FAMILY-SYRPHIDAE-FLOWER FLIES

 

The size of hoverflies varies, depending on the species.  Some are small, elongate and slender, while others are large, hairy, yellow, and black. They are brightly colored, with spots, stripes, and bands of yellow or brown covering their bodies. Due to this coloring, they are often mistaken for wasps or bees; despite this, hoverflies are harmless. Hoverflies are distinguished from other flies by a spurious vein, located parallel to the fourth longitudinal wing vein. Their bodies are densely covered by hair, and adults feed mainly on nectar and pollen.  They also hover around flowers, lending to their common

        

        

 

Hover fly wing illustrating characteristic spurious vein.  Image courtesy of http://commons.wikimedia.org/wiki/User:Lycaon.  Adult Hover Fly

Adult hover flies are often found near flowers and usually do a lot of hovering. While the adults of most flower flies are nectar feeders, the larval stage is highly predaceous on aphids and other soft-bodied insects.  Females lay single eggs on the plants near aphid populations. Each female can lay several hundred eggs. The eggs hatch after 2 or 3 days. The larvae are small maggots that feed voraciously on aphids. In its life span one larva can eat up to 400 aphids. The larval stage has 3 instars which together take about 2 weeks to develop into a pupa. 

 

                                                A Typical Syrphid \Fly Larva Consuming an Aphid.  Image Courtesy of Clemson University Entomology.

 

Not all syrphid flies are predatory in the larval stage.  A well-known example is the drone bee.  The adult of this species closely mimics a honey bee drone.  It is nearly worldwide in distribution.  The larval stage is called the rat tailed maggot which is a fitting description considering its appearance.  A characteristic feature of rat-tailed maggots is a tube-like, three segmented, telescoping breathing siphon located at their posterior end. This acts like a snorkel, allowing the larva to breathe air while submerged. The siphon is usually about as long again as the maggot's body (20 mm when mature), but can be extended as long as 150 mm. It is this organ that gives the larva its common name. It lives in stagnant, oxygen-deprived water, with a high organic content. It is fairly tolerant of pollution and can live in sewage lagoons and cesspools.

These larvae, commonly called "mousies" are cultured and sold as fish bait. They are especially popular in ice fishing. There have occasionally been documented cases of human intestinal myiasis of the Rat-tailed maggot larvae. Symptoms can be none (asymptomatic) to abdominal pain, nausea and vomiting. Infection can be caused by ingestion of contaminated food or water but doubts have been expressed that accidentally ingested fly larvae could survive in the gastrointestinal tract.  Some have proposed an alternative called "rectal myiasis". Flies, attracted to feces, may deposit their eggs or larvae near or into the anus, and the larvae then penetrate further into the rectum. They can survive feeding on feces at this site, as long as the breathing tube reaches towards the anus.

                                                                                      

                                                                                    

 

The Drone Bee, also Known as the H-bee.  Image Courtesy of Dave Britton.  Rat Tail Maggot Larvae.  Image Courtesy of C Johnson-Walker

                 

FAMILY-ASILIDAE-ROBBER FLIES

 

The family Asilidae contains about 7,100 described species worldwide. All robber flies have stout, spiny legs, a dense moustache of bristles on the face (mystax), and 3 simple eyes (ocelli) in a characteristic depression between their two large compound eyes. The mystax helps protect the head and face when the fly encounters prey bent on defense. The antennae are short, 3-segmented, sometimes with a bristle-like structure called an arista. The short, strong proboscis is used to stab and inject victims with saliva containing neurotoxic and proteolytic enzymes which paralyze and digest the insides; the fly then sucks the liquefied meal through the proboscis. Many species have long, tapering abdomens, sometimes with a sword-like ovipositor. Others are fat-bodied bumblebee mimics. Adult robber flies attack other flies, beetles, butterflies and moths, various bees, ants, dragon and damselflies, Ichneumon wasps, grasshoppers, and some spiders.

Adults lay eggs into soil or plants. The larvae are often found in decaying organic matter, such as dung heaps and rotting logs, but are also found in ordinary soil. In most species the larvae are omnivorous and are known to eat the eggs and larvae of other insects. Their life cycle ranges from 1 to 3 years

 

                                                                                     

 

Typical Robber Fly with Robust Thorax, Long Tapering Abdomen and Bearded

Mouthparts.  Left Image Courtesy of IO Vision, Dexter Sear.

 

BOMBYLIIDAE-BEE FLIES

 

Bombyliidae is a large family of flies with hundreds of genera, although their life cycles are not well known. Adults generally feed on nectar and pollen, thus are pollinators of flowers. They superficially resemble bees, thus are commonly called bee flies, and this may offer the adults some protection from predators.

The larval stages are predators or parasitoids of other insect eggs and larvae. The adult females usually deposit eggs in the vicinity of possible hosts, quite often in the burrows of beetles or wasps/solitary bees. Where most often in the insect world parasitoids are highly specific in the host species that they will infect, some bombyliids are opportunistic and will use a variety of hosts.

While bombyliids have a great variety of species, rarely are individuals of any one species abundant, and this is perhaps one of the poorest known families of insects relative to its size. There are at least 4,500 described species, and probably thousands as of yet undescribed.

                                                                                           

                                                                                                                                         Bee Fly Adult.

This is a frequently overlooked family from the standpoint of biological control.  They are predatory in both the adult and stage and are quite common in many agricultural systems.  The long-legged flies make up a large family with more than 7,000 described species in about 230 genera distributed worldwide. They are generally small flies with large, prominent eyes and a metallic cast to their appearance, though considerable variation is observed. Most have long legs, though some do not. The males often have enlarged genitalia which can be useful for species recognition. The adults are predatory on other small animals.

This family includes the subfamily Microphorinae, formerly placed in Empididae, and briefly considered a separate family.

Dolichopodidae give visual (as distinct from chemical or other) signals during courtship; many studies have been undertaken of this behavior. The larvae occupy a wide range of habitats, both terrestrial and aquatic, and can be predators or scavengers.

 

                                                                      

 

                                                                                                                          Long Legged Flies. Right Image en Wikipedia.

 

 

                                                                                                           Family Empididae-Dance Flies

 

Empididae is a family of flies with over 3,000 described species occurring worldwide, but the majority is found in the Holarctic. They are mainly predatory flies and exhibit a wide range of forms but are generally small to medium sized, non-metallic and rather bristly.

Common names for members of this family are dagger flies (referring to the sharp piercing mouthparts of some species) and balloon flies. The term "dance flies" is sometimes used for this family.

                                                                          

                                                                                                          

                                                                   Dance Fly and Maiting Pair with Nuptuial Gift.   Image Courtesy Onno Zweers

 

Dance flies exhibit unique mating behaviors, and have been the subject of a number studies seeking to understand the operation of sexual selection.  In “typical” dance flies, males capture (but do not eat) insect prey, then form specialized aerial mating swarms. Females fly into the swarm and choose a mate, which then offers the prey as a nuptial gift for the female to feed on during mating. Unlike related empidoid flies, in which both sexes are predatory, many adult dance flies feed mainly on flower nectar and eat insect prey only during mating.  This presumably makes females dependent on males for protein to complete egg development.  These behaviors have probably heightened the strength of sexual selection for dance flies, and led to the evolution of unusual structures and behaviors for attracting mates.

There are many variations on this typical set of behaviors.  For example, some groups do not form aerial swarms or present nuptial gifts.  In several groups, males are choosy, and swarms are composed mainly of conspicuously marked females advertising to males.  In other species, males give the female non-edible gifts of dried insects or plant parts.  "Balloon flies" (certain species of Hilara and Empis) present as a nuptial gift a balloon made of silk or froth, which may be empty or contain a small insect.  Some Empididae, such as the European species Hilara maura, have an elaborate courtship ritual in which the male wraps a prey item in silk and presents it to the female to stimulate copulation.

Empidid larvae are also largely predatory (although some are scavengers) and occupy a wide range of habitats, both aquatic and terrestrial.

 

                                                                                                            FAMILY-CALLIPHORIDAE-BLOW FLIES

Blow flies have a characteristic green, copper or blue metallic coloration.  This, in combination with their “typical” (appearing as a stereotype fly) flulike appearance, is diagnostic. Also note the white lobe-like extension of the wing (yellow arrow).  This is a calypter and is characteristic of a number of the common flies (blowflies, house flies, flesh flies, and tachinid flies) discussed in this CD. The larvae feed on dead animals, excrement, and occasionally living flesh.  These flies are generally considered beneficial, as they are key elements in the decaying process of dead animals.                                         

             

 Adult Blow Flies. 

Some species of blow flies will also attack living animals.  An infestation of a living animal is referred to as myiasis.  In the United States most cases of traumatic myiasis (infesting wounds) are more or less confined to rotting tissues.  Typically these flies deposit their larvae or eggs that hatch and feed chiefly on the decaying tissue associated with wounds.  This feeding activity rarely harms the person or animal, and in some cases can actually be beneficial.  It was found during World War I that wounded troops not found immediately but left in the battlefield for a few days developed less of certain types of deep-seated infections than those soldiers taken directly to the hospital.  The wounds of the soldiers left in the field were infested with fly maggots, which secreted a material named alantoin, a natural antibiotic. The introduction of blow fly maggots into wounds is still practiced worldwide by many primitive people and the use of sterilized maggots for this purpose is now receiving some attention by physicians in the United States.

We once had a loop eared rabbit which has a large flap of skin below its chin call a dewlap.  Every time it drank water this structure became wet.  As a result a local bow fly made a hit (deposited a few hundred eggs) on this structure and by the time we discovered it, the maggots were feeding on the entire underside of the still living animal.  Of course the animal had to be destroyed.

 

Secondary and Primary Screwworms. Cochliomyia macellaria and Cochliomyia hominivorax.  These are metallic green to bluish green in major coloration, with setae on the dorsal surface of the stem vein, orange gena, pale white anterior spiracles, filiform palps, and three black longitudinal stripes (vittae) on the notum of the thorax. The screwworm is name after the fact that the larvae possess small spines on each body segment that resemble a screw’s threads.

This entire life cycle lasts an average of 21 days at prime conditions (preferably a warm, moist environment), and can last as long as two to three months in colder climates. Female Cochliomyia only lay eggs once in a lifetime and can lay anywhere from 100 to 400 in a clutch. Females usually lay their eggs on the edge of an open wound. The warm and moist conditions are the perfect combination of home and food source. The nose, mouth, or anal areas of a host are especially prone to Cochliomyia oviposition.

                                                                                    

 The adult of a primary screwworm, a major cattle pest from Mexico to South America.  Image courtesy Marcelo de Campos Pereira, Sao Paolo, Brazil.

The cream colored larvae hatch approximately 12-21 hours after the eggs have been laid.  The primary screwworm larvae will dive head-first into whatever food source is nearest, and burrow deeper, eating into live flesh if available. This results in a pocket-like lesion that causes severe pain to the host. On the other hand secondary screwworm larvae only feed on the necrotic tissue of a wound. After 5 to 7 days, the larvae drop and move away from the food source to pupate. The larvae burrow into the first layer of topsoil, beneath leaves or garbage and pupate. This stage can last from 7 days at a warm temperature to as long as two months if the weather is much colder. Adults breed only once in their lifetime. Sexually mature adults typically breed between 3-4 days after hatching from the pupa. Males mature rapidly, and will spend their time waiting and eating on nearby vegetation and the nectar of flowers. The females, however, are predacious, and will feed on the fluids from live wounds. The females can fly long distances to find a mate. The adult flies of this species will live approximately two to three weeks.

They tend to reproduce only on the flesh of a living host. Unlike most other maggots, the hominivorax maggots will attack and consume healthy living tissue along with decaying tissue (hominivorax literally translates to “man eating”). About 12-21 hours after the larvae hatch, they crawl into the wound and immediately begin to feed and burrow deeper perpendicular to the skin surface eating into live flesh, again resembling a screw being driven into an object. The larvae will then continue to feed on the wound fluids and the animal’s tissue. After 5-7 days, the larvae grow and depart from the wound to burrow into the soil and pupate. The pupal period varies from a week to upwards of 2 months, depending on the soil temperature. Adults breed only once during their lifetime, which is close to 20 days. 

Cochliomyia hominivorax has been present in North America from ancient times, and is even referenced in some ancient indigenous dialogues. Mention of the species has also been found in some various texts from the time of the Spanish American colonies. Control of the adult flies was an exercise in futility in the United States for quite some time, until the advent in 1958 of the sterile insect technique. Proposed by a pair of scientists, Edward F. Knipling and Raymond C. Bushland, and rapidly adopted by the United States Department of Agriculture, the technique centers on a unique reproductive handicap that prevents female hominivorax flies from reproducing more than once in their life-spans. The scientists reasoned that if it were possible to clinically sterilize and release huge numbers of male hominivorax as breeding time approached, fertile males might be out-competed and the majority of female flies would lay sterile eggs. Irradiating the males was the method used for sterilization. As the agricultural industry was losing millions of dollars annually due to treatment and loss of fly-struck animals, this solution was quickly approved for testing. It was first applied on a large scale in the state of Florida, due both to the severity of the problem there and to the state’s unique island-mimicking geography, which allowed for relative isolation of the Florida hominivorax population. Following eradication of Florida’s Primary screwworm population in 1959 the program was applied throughout the southern United States, and eventually adopted through much of Mexico in 1972 and parts of Central and South America. The hominivorax was completely eradicated from the southern United States in 1966 and from Mexico in 1991. Primary screwworm has been effectively eliminated in the United States and Mexico. Livestock there continue to be vulnerable, however, and strict laws regarding animal inspection and reporting of suspected infestations remain in place.

The largest documented infestation of hominivorax myiasis outside of the North American continent was found in sheep located in Northern Africa in the year 1989. The myiasis spread rapidly infecting numerous herds in the territory during the following months. The infested area was 25,000 square kilometers, and reached more than 2.7 million animals between the Mediterranean Sea and the Sahara desert. From July 1989 to April 1991 there were more than 14,111 documented cases of large scale myiasis due to the Cochliomyia hominivorax species. Traditional control methods were unable to prevent this screw-worm spreading in Africa and therefore the sterile insect technique was used. For the African outbreak, sterile flies were made and shipped over from a factory in Mexico. Then the 1,260 million sterile flies were released to mate in the infested 15,000 kilometer area. Soon after the fly population shrunk and became manageable. This successful program cost almost 100 million US dollars and several months to complete. After this historical outbreak in Africa the sterile male technique was mastered and is now in use to lower the number of flies in areas of Central and Southern America. The inaccessibility of some areas that the fly inhabits, language differences, and the need of constant vigilance has slowed the eradication of this species in parts of Central and Southern America. This eradication was declared the most efficient and successful international animal health program in the history of the United Nations Organization.

Secondary Screwworm, Cochliomyia macellaria. This is a flesh-eating fly whose larvae consume only necrotic tissue, either that of carrion or of an animal or human host (myiasis). This important distinction between macellaria and hominivorax was not understood for much of medical history; myiasis of humans and animals was viewed as universally disastrous. However, as medical understanding of the process of tissue breakdown and infection progressed, it began to be observed that wounds with specific types of maggot infestation actually had a decreased severity and duration of infection. This progressed to the point of macellaria being applied in some cases as surgical maggots. However, the negative connotation surrounding the word “screwworm” has persisted, and the largely-harmless macellaria are often blamed for myiasitic attacks that hominivorax are actually responsible for. This should not be interpreted to mean that macellaria is not an avid consumer of flesh; Cochliomyia macellaria are routinely among the first colonizers of carrion, and in forensic cases have long had a habit of literally consuming evidence. The macellaria are especially abundant on corpses and carrion in warm, direct sunlit areas. Fortunately, with the recent advent of molecular evidence, macellaria maggots removed from a body and boiled to sterility can now provide vital information regarding a victim and determining a post mortem interval. Forensic entomologists can use various extraction methods to test the composition of the alimentary canal of the larvae to determine if the victim had any drugs or mind altering substances in their system before they were killed. It is important however for the forensic entomologist to determine whether the Old World Screwworm, Chrysomya rufifacies, is present in the maggot masses on the body. This is because Chrysomya rufifacies is usually after the macellaria in the succession of colonizing a body and the rufifacies second and third instar larvae are facultatively predacious. This could result in a PMI post mortem interval) being off by a few days at the most if the rufifacies were to predate upon all of the macellaria larvae.

Screwworms and Human Myiasis.  In 1935, prior to its eradication in the United States, there were over a hundred cases of human myiasis in Texas alone.  In one documented case, a female fly deposited her eggs up the nostril of a man who had a cold.  Apparently, the fly was attracted to his nasal discharge.  The first symptoms were those of a severe cold.  As the larvae cut away through the various tissues of the head, the victim became slightly delirious and complained of intense misery and discomfort in the nose and head.  When the larvae finally cut through the soft pallet, his speech was impaired.  Despite attempts to remove the larvae, the patient had a relapse after a short recovery as the Eustachian tubes were invaded.  The tissue damage was extensive and the head and face showed the characteristic swelling of screwworm myiasis. During the autopsy over one hundred larvae were removed from the man’s brain.

Cochliomyia hominivorax are primary, obligate parasites in the larval stage, and as a result of this are capable, unlike their secondary screwworm counterparts, of initializing the penetration of the skin barrier to create an entry wound. Despite this, they are most commonly seen as colonizers of previously-existing wounds, and will frequently be hatched from eggs laid at the perimeter of the wound. Once the infestation commences, a dark brown or reddish-brown discharge will begin leaking from the wound, sometimes accompanied by an unpleasant smell as the flesh begins to become necrotic. This is often the first sign in human victims that something is amiss, and will often initialize consultation of a professional. As the infestation increases, the victim will begin to experience escalating tissue irritation, and in the case of domesticated animals may be observed to become withdrawn, listless, and anorexic.

Treatment of the victim can be time-consuming and, due to the high incidence of secondary infection, frustrating, but with decisive treatment, a surprisingly positive result is often achieved in all but the worst cases. The obvious first step is the manual removal of the maggots, generally using tweezers or forceps to seize the larva at the posterior end as the spiracles emerge to allow respiration. Once all larvae have been removed, a topical antibiotic smear will be applied, often with an oral antibiotic accompaniment. Necrotic tissue may need to be cut out, which can be a painful process. A loose dressing is essential to allow continued fluid drainage form the wound.

Both Cochliomyia hominivorax and Cochliomyia macellaria thrive in tropical areas which are warm and humid. Cochliomyia macellaria is the most common Cochliomyia species found in North America. This species is distributed throughout northern South America, Central America, Caribbean Islands, United States, and southern Canada. Cochliomyia hominivorax was distributed throughout the northern South America, Central America, Caribbean Islands, and the United States prior to the use of the Sterile Insect Technique, after which it was eradicated from the U.S. and Mexico. However, the bordering Central American countries serve a challenge to keep the species eradicated since these countries still have populations of this fly. Many of these countries continue to implement eradication programs.

 

                                                                                                      Sterile Male Technique-Success and Failure. 

This is a method of biological control, whereby millions of sterile insects are released. The released insects are normally male as it is the female that causes the damage, usually by laying eggs in the crop, or, in the case of mosquitoes, taking a blood meal from humans. The sterile males compete with the wild males for naturally occurring female insects. If a female mates with a sterile male then it will have no offspring, thus reducing the next generation's population. Repeated release of insects can eventually wipe out a population, though it is often more useful to consider controlling the population rather than eradicating it.

The technique has successfully been used to eradicate the Screw-worm fly (Cochliomyia hominivorax) in areas of North America. There have also been many successes in controlling species of fruit flies, most particularly the Medfly (Ceratitis capitata), and the Mexican fruit fly (Anastrepha ludens).

Labortory reared pupae are typically sterilized in with radiation (Cobalt 60), which might weaken the newly sterilized insects, if doses are not correctly applied, making them less able to compete with wild males. However, other sterilization techniques are under development which would not affect the insects' ability to mate.

The technique was pioneered in the 1950s by American entomologists Dr. Raymond C. Bushland and Dr. Edward F. Knipling. For their achievement, they jointly received the 1992 World Food Prize. Raymond Bushland and Edward Knipling first developed the technique to eliminate screwworms preying on warm-blooded animals, especially cattle herds. With larvae that invade open wounds and eat into animal flesh, the flies were capable of killing cattle within 10 days of infection. In the 1950s, screwworms caused annual losses to American meat and dairy supplies that were projected at above $200 million. Screwworm maggots are also known to parasitize human flesh.

The goal of Bushland and Knipling to find an alternative to chemical pesticides in controlling the devastation by these insects began in the late 1930s when both scientists were working at the United States Department of Agriculture Laboratory in Menard, Texas. At that time, the screwworm was decimating livestock herds across the American South. Red meat and dairy supplies were also affected across Mexico, Central America, and South America.

In 1954, the technique was used to completely eradicate screwworms from the 176-square-mile (460 km²) island of Curaçao, off the coast of Venezuela. Screwworms were eliminated in a span of only seven weeks, saving the domestic goat herds that were a source of meat and milk for the island people. Screwworm larvae were originally reared on meat and then whale blubber.  Today a fiber based artificial diet is used since there is literally a need for trillions of these insects.

During the 1960s and 1970s, the technique was used to control the screwworm population in the United States. The 1980s saw Mexico and Belize eliminate their screwworm problems, and eradication programs have progressed through all of Central America, with a sterile male barrier having been established in Panama to prevent reinfestation from the south. In 1991, Knipling and Bushland's technique halted a serious outbreak in northern Africa. Similar programs against the Mediterranean fruit fly in Mexico and California use the same principles. In addition, the technique was used to eradicate the melon fly from Okinawa and has been used in the fight against the tsetse fly in Africa.

The technique has been able to suppress insects threatening livestock, fruit, vegetable, and fiber crops. The technique has also been lauded for its many environmentally sound attributes: it uses no chemicals, leaves no residues, and has no effect on non-target species.

Proven effective in controlling outbreaks of a wide range of insect pests throughout the world, the technique has been a boon in protecting the agricultural products to feed the world’s human population. Both Bushland and Knipling received worldwide recognition for their leadership and scientific achievements, including the World Food Prize. Their research and the resulting Sterile Insect Technique were hailed by former U.S. Secretary of Agriculture Orville Freeman as "the greatest entomological achievement of (the 20th) century."

Tse-Tse Fly. The sterile fly is an innovative solution to the problem of African trypanosomiasis (sleeping sickness), and is being developed by the United Nations and the International Atomic Energy Agency (IAEA), building on their experience of similar programs over past decades against the fruit fly in Australia and Africa.

Sleeping sickness or African trypanosomiasis is a parasitic disease in humans. Caused by protozoa of genus Trypanosoma and transmitted by the Tsetse fly, the disease is endemic in certain regions of Sub-Saharan Africa, covering about 36 countries and 60 million people. It is estimated that 300,000 - 500,000 people are infected, and about 40,000 die every year. Three major epidemics have occurred in the past hundred years, in 1896 - 1906, 1920, and 1970.

Studies of the tsetse fly show that females generally only mate once in their lifetimes and very rarely mate a second time. Once a female fly has mated, she can then produce continual offspring throughout her short life.

Using this information, the International Atomic Energy Agency has developed a process of irradiating male Tsetse flies that have been specially bred. This process of irradiation sterilizes the male. These sterilized male flies are then released into areas where sleeping sickness is prevalent, and then mate with the females. Because the male is sterile, and the females mate only once, the population of Tsetse flies in the affected area will drop. Studies have shown that this process has been very effective in preventing sleeping sickness in people who live in the area.

Since sleeping sickness is fatal without treatment and infected people can be without symptoms for months, the release of sterile flies into affected areas leads to greater levels of health and economic activity.

Other Successes.

§         Screwworm fly Cochliomyia hominivorax - eradicated from the United States, Mexico, the whole Central America, and Libya.

§         Mexican fruit fly Anastrepha ludens (Loew) eradicated from most of northern Mexico.

§         Tsetse fly eradicated from Zanzibar.

§         Medfly Ceratitis capitata (Wiedemann) - eradicated from northern part of Chile and southern part of Peru and southern part of Mexico.

§         Melon fly Bactrocera cucurbitae (Coquillett) eradicated from Okinawa, Japan.

§         Extensive table of the application of sterile insect technique.

Other Potential Targets of Interest.

§         Anopheles mosquito - Malaria^l vector, example Anopheles arabiensis.

§         Tsetse fly (Glossina spp) - sleeping sickness vector.

§         Painted Apple Moth (Lepidoptera: Lymantriidae) in Auckland, New Zealand.

§         Aedes mosquitoes, vectors for filariasis, Dengue and yellow fever.^[9]

§         Continuing use across the world against various fruit fly species, including Medfly, Caribbean and Mexican fruit fly (Nth, Sth and Central America), Queensland fruit fly in Australia (Bactrocera tryoni) and several other Bactrocera sp. across Australia, Asia and Oceania. The IAEA lists 36 different fruit fly SIT facilities across the globe, on all six inhabited continents  and provides information on the doses of radiation used in the control of pest insects and mites of agricultural, commercial or quarantine significance. It includes data on both the radiation dose required for the disinfestation of generic commodity groups, fresh and durable, and also the radiation dose used to induce sterility for pest control through the sterile insect technique.

Existing Problems

-In some cases it is essential to use repeated insecticide treatment in order to reduce an existing population of the target insect prior release of the sterile males.  The whole idea of the technique is to release overwhelming number of sterile males (as opposed to natural males) in order to increase the chances of a natural mating with a sterile male as opposed to a natural male. In some cases it is difficult to separate the male from the females (those to be sterilized), though this can be easily performed on Medfly and screwworm, for example.

-Radiation treatment in some cases effect the health of males (making them less competitive as opposed to natural males), so sterilized insects in such cases are at a disadvantage when competing for females.

-The technique is species specific, for instance: there are 22 species of Tsetse fly in Africa, and the technique must be implemented separately for each.

-Standard operating procedures of mass rearing and irradiation do not leave room for mistakes. Since the fifties, when SIT was first used as a means for pest control, several failures have occurred in different places around the world where non-sterilized artificial produced insects were released before the problem was spotted.

-Application to large areas should be long lasting, otherwise migration of wild insects from outside the control area could repopulate.

New Techniques.

-The major drawback to this technique is in the poor countries where it is often prohibitive the cost of producing such a large number of sterile insects.

-A method using recombinant DNA technology to create genetically modified insects called RIDL (Release of Insects carrying a Dominant Lethal) is under development by a company called Oxitec. The method works by introducing a repressible "Dominant Lethal" gene into the insects. This gene kills the insects but it can be repressed by an external additive, which allows the insects to be reared in manufacturing facilities. This external additive is commonly administered orally, and so can be an additive to the insect food. The insects can also be given genetic markers, such as fluorescence, that make monitoring the progress of eradication easier.

There are potentially several types of RIDL, but the more advanced forms have a female-specific dominant lethal gene. This avoids the need for a separate sex separation step, as the repressor can be withdrawn from the final stage of rearing, leaving only males.

These males are then released in large numbers into the affected region. The released males are not sterile, but any female offspring their mates produce will have the dominant lethal gene expressed, and so will die. The number of females in the wild population will therefore decline, causing the overall population to decline.

Using RIDL means that the males will not have to be sterilized by radiation before release, making the males healthier when they need to compete with the wild males for mates.

Progress towards applying this technique to mosquitos has been made by researchers at Imperial College London who created the world's first transgenic malaria mosquito.

A similar technique is the daughterless carp, a genetically modified organism produced in Australia by the CSIRO in the hope of eradicating the introduced carp from the Murray River system. As of 2005, it was undergoing tests to assess the risks of releasing it into the wild.

Biotechnological approaches based on genetically modified organism (transgenic organisms), still under development, are promising; however since no legal framework exists to authorize the release of such organisms in the nature ^[14][15], sterilization by irradiation remains the most used technique. A meeting was held at FAO headquarters in Rome, 8 to 12 April 2002 on "Status and Risk Assessment of the Use of Transgenic Arthropods in Plant Protection". The resulting proceedings of the meeting have been used by NAPPO (North American Plant Protection Organization) to develop NAPPO Regional Standard No. 27 on "Guidelines for Importation and Confined Field release of Transgenic Arthropods", which provides the basis for the rational development of the use of transgenic arthropods.

SIT programs will benefit tremendously if genetic methods can be developed that enable only male insects to be reared as has already been done for the medfly. Also more appropriate artificial diets for larvae, and hormonal, nutritional, microbiological, and semiochemical treatments for adults, could make major contributions through improved economy and insect quality.

Economic benefits of SIT have been demonstrated in various cases. Direct benefits of screwworm eradication to the North and Central American livestock industries are estimated to be over $ 1.5 billion/ year, compared with a total investment over half a century of close to $ 1 billion. Mexico protects a fruit and vegetable export market of over $ 3 billion/year through an annual investment of ca. $ 25 million, and medfly-free status has been estimated to have opened markets for Chile’s fruit exports of up to $ 500 million.   When implemented on an area-wide basis and with economies of scale in the mass rearing process, the use of SIT for suppression is cost competitive with conventional control, in addition to its environmental benefits.

Maggot Theropy. Maggot therapy (also known as maggot debridement therapy (MDT), larval therapy, larva therapy, larvae therapy, biodebridement or biosurgery) is a type of biotherapy involving the intentional introduction of live, disinfected maggots (fly larvae) into the non-healing skin and soft tissue wound(s) of a human or animal for the purposes of selectively cleaning out only the necrotic tissue within a wound (debridement), disinfection, and promotion of wound healing.

                                                                                     

                                                                                     Maggots Feeding In Wound. Image Courtesy of PD-USGOV-HHS-NIH

Written records have documented that maggots have been used since antiquity as a wound treatment. There are reports of the successful use of maggots for wound healing by Maya Indians and Aboriginal tribes in Australia. There also have been reports of the use of maggot treatment in Renaissance times. During warfare, many military physicians observed that soldiers whose wounds had become colonized with maggots experienced significantly less morbidity and mortality than soldiers whose wounds had not become colonized. These physicians included Napoleon’s surgeon general, Baron Dominique Larrey, who reported during France's Egyptian campaign in Syria, 1798–1801, that certain species of fly destroyed only dead tissue and had a positive effect on wound healing.

Dr. Joseph Jones, a ranking Confederate medical officer during the American Civil War, is quoted as follows, "I have frequently seen neglected wounds ... filled with maggots ... as far as my experience extends, these worms only destroy dead tissues, and do not injure specifically the well parts." The first therapeutic use of maggots is credited to a second Confederate medical officer Dr. J.F. Zacharias, who reported during the American Civil War that, "Maggots ... in a single day would clean a wound much better than any agents we had at our command ... I am sure I saved many lives by their use." He recorded a high survival rate in patients he treated with maggots.

During World War I, Dr. William S. Baer, an orthopedic surgeon, recognized on the battlefield the efficacy of maggot colonization for healing wounds. He observed one soldier left for several days on the battlefield who had sustained compound fractures of the femur and large flesh wounds of the abdomen and scrotum. When the soldier arrived at the hospital, he had no signs of fever despite the serious nature of his injuries and his prolonged exposure to the elements without food or water. When his clothes were removed, it was seen that "thousands and thousands of maggots filled the entire wounded area." To Dr. Baer's surprise, when these maggots were removed "there was practically no bare bone to be seen and the internal structure of the wounded bone as well as the surrounding parts was entirely covered with most beautiful pink tissue that one could imagine." This case took place at a time when the death rate for compound fractures of the femur was about 75-80%.

While at Johns Hopkins University in 1929, Dr. Baer introduced maggots into 21 patients with intractable chronic osteomyelitis. He observed rapid debridement, reductions in the number of pathogenic organisms, reduced odor levels, alkalinization of wound beds, and ideal rates of healing. All 21 patients' open lesions were completely healed and they were released from the hospital after two months of maggot therapy.

After the publication of Dr. Baer's results in 1931, maggot therapy for wound care became very common, particularly in the United States. The Lederle pharmaceutical company commercially produced "Surgical Maggots", larvae of the green bottle fly, which primarily feed on the necrotic tissue of the living host without attacking living tissue. Between 1930 and 1940, more than 100 medical papers were published on maggot therapy. Medical literature of this time contains many references to the successful use of maggots in chronic or infected wounds including osteomyelitis, abscesses, burns, sub-acute mastoiditis, and chronic empyema.

More than 300 American hospitals employed maggot therapy during the 1940s. The extensive use of maggot therapy prior to World War II was curtailed when the discovery and growing use of penicillin caused it to be deemed outdated.

[With the advent of antibiotic-resistant bacteria, Dr. Ronald Sherman, a physician previously at the University of California, Irvine, sought to re-introduce maggot therapy into modern medical care. In 1989, he set up fly breeding facilities at the Veterans Affairs Medical Center in Long Beach, California, in order to use maggots for the treatment of wounds. That year, using a Paralyzed Veterans of America grant, he initiated a prospective controlled clinical trial of maggot therapy for spinal cord patients with pressure ulcers who had failed two or more courses of conventional wound care.

The therapeutic maggot used by Sherman is a strain of the green bottle fly (Phaenicia sericata) and marketed under the brand name Medical Maggots.

                                                                                  

                                                                         Adult of Phaenicia sericata (Green Bottle Fly). (. Image Courtesy of Calibas.

Over fifty scientific papers have been published that describe the medical use of maggots. Six thousand maggot therapy patients have been included in case histories or other studies. About 400 patients have been documented within clinical studies. In the medical literature, limb salvage rates with maggot therapy are about 40% to 50%. Some report success rates of 70% to 80%.

In a 2007 preliminary trial, maggots were used successfully to treat patients whose wounds were infected with MRSA, a bacterium (Staphylococcus aureus) with resistance to most antibiotics. Some of these strains include "flesh eating bacteria" causing frequent deaths upon infection of deep tissue. In these cases maggots clean up the already dead tissue thus preventing further infection spread.

In 1995, a handful of doctors in 4 countries were using maggot therapy. Today, any physician in the U.S. can prescribe maggot therapy. There are over 800 health care centers in the United States that have utilized maggot therapy. Over 4,000 therapists are using maggot therapy in 20 countries. Approximately 50,000 treatments were applied to wounds in the year 2006.

The use of maggots to clean dead tissue from animal wounds is part of folk medicine in many parts of the world. It is particularly helpful with chronic osteomyelitis, chronic ulcers, and other pus-producing infections that are frequently caused by chafing due to work equipment. Maggot therapy for horses in the United States was re-introduced after a study published in 2003 by veterinarian Dr. Scott Morrison. This therapy is used in horses for conditions such as osteomyelitis secondary to laminitis, sub-solar abscesses leading to osteomyelitis, post-surgical treatment of street-nail procedure for puncture wounds infecting the navicular bursa, canker, non-healing ulcers on the frog, and post-surgical site cleaning for keratoma removal.

Maggots are applied by containing them in a cage-like dressing over the wound for two days. The maggots may be allowed to move freely within that cage, with the wound floor acting as the bottom of the cage; or the maggots may be contained within a sealed pouch, placed on top of the wound. The dressing must be kept air permeable because maggots require oxygen to live. When maggots are satiated, they become substantially larger and seek to leave the site of a wound. Multiple two-day courses of maggot therapy may be administered depending on the severity of the non-healing wound.

Maggots can never reproduce in the wound since they are still in the larval stage and too immature to do so. Reproduction can only occur when they become adult flies and mate.

The maggots have three principal actions reported in the medical literature:

§         Disolving rotting tissue from wounds (debridement);

§         disinfecting the wound by killing bacteria; and

§         stimulating wound healing.

The debridement of necrotic tissue is a prerequisite for successful wound care. If debridement does not take place, wound repair is significantly impaired. Necrotic tissue in the wound is not only an obstacle for localized treatment, but becomes an ideal breeding ground for bacteria and may lead to gangrene, necessitating limb amputation, and potentially fatal sepsis (infection of the blood).

Surgeons cannot be very precise in debriding dead tissue while leaving living tissue. The human eye is simply not very discriminating in identifying healthy tissue from necrotic tissue, and surgeons only have a very limited time to operate while their patient is under anesthesia. Consequently, surgeons use their scalpels to remove far more viable tissue than is needed, producing a wound larger than necessary that has more bleeding and a greater chance of becoming infected. Patients also experience more wound-associated pain after removal of healthy tissue. Wound care therapists can find themselves needing to remove necrotic tissue from a wound day after day, deeper and deeper; this is impractical as surgeons simply do not have the time to perform frequent surgical debridements. The requirement for frequent surgical debridement complicates and lengthens wound healing, lengthening hospital stays and increasing costs.

In maggot therapy, a large number of small maggots selectively consume only necrotic tissue far more precisely than is possible in a normal surgical operation, and can debride a wound in a day or two. These maggots do not damage healthy tissue: they operate with precision at the boundary between healthy and necrotic tissue. They derive nutrients through a process known as "extracorporeal digestion" by secreting a broad spectrum of enzymes that liquefy necrotic tissue, and absorb the semi-liquid result within a few days.

Any wound infection is always a serious medical complication. Infected living tissue cannot heal. If the wound is infected with an antibiotic-resistant bacterial strain, it becomes difficult or impossible to treat the underlying infection and for any healing to occur. Wound infection could further be limb- and life-threatening. When maggots successfully debride a necrotic wound, a source of wound infection is removed.

For wounds already infected, maggot therapy is effective even against antibiotic-resistant bacteria. Maggot secretions were first experimentally shown in the 1930s to possess potent antimicrobial activity.  Secretions believed to have broad-spectrum antimicrobial activity include allantoin, urea, phenylacetic acid, phenylacetaldehyde, calcium carbonate, and proteolytic enzymes. Bacteria not killed by these secretions are subsequently ingested and broken down within the maggots.

In vitro studies have shown that maggots inhibit and destroy a wide range of pathogenic bacteria including methicillin-resistantStaphylococcus aureus (MRSA), group A and B streptococci, and Gram-positive aerobic and anaerobic strains. In a published review of five patients who were infected with MRSA, some having failed conventional therapy for up to 18 months, maggot therapy was able to eliminate the bacterium from all wounds in an average of 4 days.  Maggot therapy therefore represents a highly cost-effective method for managing MRSA infection without exacerbating the problems of antibiotic resistance.

Maggot therapy has been shown by multiple researchers to have wound healing properties. Maggot secretions appear to amplify the wound healing . Recent studies have shown that maggot secretions are able to stimulate the growth of human fibroblasts and slow-growing chondrocytes. Chondrocyte proliferation, as well as the synthesis of cartilage-specific type II collagen, increases in the maggot secretion environment. Micromassage of the wound by maggot movement is further thought to stimulate the formation of granulation tissue and wound exudates by the host. The precise mechanism(s) of maggot stimulation of wound healing is an active area of study by several researchers. Maggot secretions also contain a substance called allantoin (also found in many shaving gels) which has a soothing effect on the skin.

There are limitations of maggot therapy. The wound must be of a type which can actually benefit from the application of maggot therapy. A moist, exuding wound with sufficient oxygen supply is a prerequisite. Not all wound-types are suitable: wounds which are dry or open wounds of body cavities do not provide a good environment for maggots to feed. In some cases it may be possible to make a dry wound suitable for larval therapy by moistening it with saline soaks, applied for 48 hours.

Maggots have a short shelf life which prevents long term storage before use.  Patients and doctors may find maggots distasteful, although studies have shown that this does not cause patients to refuse the offer of maggot therapy. Maggots can be enclosed in opaque polymer bags to hide them from sight. Dressings must be designed to prevent any maggots from escaping, while allowing air to get to the maggots. Dressings are also designed to minimize the uncomfortable tickling sensation that the maggots often cause.

Cluster Flies-Pollenia spp. Unlike more familiar blowflies such as the bluebottle genus Phormia, they do not present a health hazard because they do not lay eggs in human food. They are strictly parasitic on earthworms; the females lay their eggs near earthworm burrows, and the larvae then infest the worms. However, the flies are a nuisance because when the adults emerge in the late summer or autumn they enter houses to hibernate, often in large numbers; they are difficult to eradicate because they favor inaccessible spaces such as roof and wall cavities. They are often seen on windows of little-used rooms. They are also sometimes known as attic flies.

The typical cluster fly Pollenia rudis is about 7 mm long and can be recognized by distinct lines or stripes behind the head, short golden-colored hairs on the thorax, and irregular light and dark gray areas on the abdomen. Cluster flies are typically slow moving.

                                                                                

                                                                                                       Cluster Flies.  Image Courtesy Richard Bartz.

 

                                                                                                              FAMILY-SARCOPHAGIDAE-FLESH FLIES

 

Members of this family are typically somewhat larger than houseflies and blow flies and have and most have 3 longitudinal black stripes on the top of the thorax (muscids have 4) and a typical checkerboard patterning on the top of abdomen.  Most flesh flies breed in carrion, dung, or decaying material, but a few species lay their eggs in the open wounds of mammals, hence their common name. Some flesh fly larvae are internal parasites of other insects. These larvae live for about 5–10 days, before descending into the soil to pupate and eventually maturing into adulthood. At that stage, they live for 5–7 days.

Some species are predatory feeding on beetles, snails, and caterpillars, especially the forest tent caterpillar. Flesh-flies, being viviparous, frequently give birth to live young on corpses of human and other animals at any stage of decomposition from recently dead through to bloated or decaying (though the latter is more common).

                                                          

                                                                                                             Adult Flesh Fy on Decaying Meat.

 

 FAMILY-MUSCICAE-MUSCID FLIES

 There are a number of economically important species in this family including the house fly, Musca domestica, which is one of the best-known insect pests in the world.  This fly has 4 longitudinal stripes on the thorax.  The eggs are laid in batches of 100-150, with a female capable of producing over 1,000 in her lifetime.  The eggs hatch in about 8-12 hours and the larvae are worm-like with no visible head area.  The larvae or maggots go through 3 successive molts that, under optimum conditions, take 2 to 5 days.  With many flies, the outer skin of the last instar larva hardens prior to pupation and forms a capsule like structure, within which is found the pupae (Figure 113). The puparium is dark and will take 3 to 4 days to develop into the adult fly.  Under ideal conditions the house fly can complete one life cycle in as little as 7 days.  With this number of eggs and speed of development these insects have a tremendous reproductive capacity.  Someone once figured out that if one female house fly in April laid all her eggs and all her offspring survived and reproduced similarly, by August there would be 191,0100,000,000,000,000,000 flies or enough to cover the earth by 43 feet.  This obviously doesn’t happen.  The limiting factor is the availability of food.  Of course, in the United States we have health codes that, when followed, greatly reduce the breeding sites of these pests

.

Common house fly, Musca domestica. Image courtesy, Clemson University Entomology.

The adult lives for about 30 days and prefers to oviposite on decomposing manure or vegetable matter.  Normally most fly infestations around the home are of local origin; however, these flies are capable of flying up to 20 miles if need be.

The house fly occasionally causes enteric myiasis.  One interesting case resulted when an elderly lady went to the doctor complaining of intestinal and stomach cramping.  After considerable consultation, a stool sample revealed living house fly maggots and pupae.  Apparently she had consumed some food that was infested with maggots.  These maggots passed through the digestive system and were basically impervious to digestive enzymes and other digestive processes.  Normally, under these conditions, maggots in the digestive system may survive but do not complete their life cycles.  Rectal myiasis has also resulted when house fly adults lay their eggs around the anus.  Upon hatching the maggot migrate up into the rectum causing considerable discomfort. (So, wipe well!)

The most important medical implication of the house fly is its potential to vector disease causing organisms.  The house fly freely enters the home, restaurants and other places where human food is available; it just as freely inhabits situations where human and animal excrement is available.  It feeds on human food and excrement!  Because the fly can only feed on liquids it regurgitates digestive enzymes from its stomach to dissolve solids.  In doing so it may also regurgitate drops of excrement.  The fly is also structurally adapted for picking up pathogens.  Its mouthparts are provided with many fine hairs and ridges that readily collect germs and filth.  The tarsi are a complex structure of fine hairs and sticky pads that enhances it potential for vectoring diseases.  Studies have indicated that a single house fly can carry as many as 6 million bacteria on its body.  Flies have been known to be contaminated with more than 100 species of pathogenic organisms, including the causative agents of amoebic and bacterial dysentery, typhoid fever, cholera, salmonella, anthrax, leprosy, yaws, trachoma, polio, and infectious hepatitis.  In addition they have been demonstrated to carry the eggs of certain pathogenic worms including pinworm, tapeworms and hookworms.

 

       The lesser house fly, a more common inhabitant of homes than the house fly.  Image courtesy of Marcelo de Campos Pereira, University Sao Paulo Brazil.

 

Lesser houseflies are prolific breeders in poultry manure, but will also breed in other moist decaying matter. The flattened, legless, greybrown maggots hatch within 24-48 hours. Hairy protuberances on their dorsal surface are thought to aid progression and floating in a semi-liquid medium. The newly hatched larvae frequently wander for a time before burrowing into a suitable food source. Larval development requires a minimum period of 8 days, during which time the larva passes through 3 stages, eventually attaining a length of 6-mm. Eggs hatch after 1 to 4 days. Each larval instar lasts 3 to 5 days. Pupae leave the semi-liquid or liquid substrate for somewhat drier places to pupate when the mated female is 10 days old. The eggs are banana-shaped, 1 mm in length and bear a pair of longitudinal ridges which assist flotation in a liquid medium. The flattened, legless, greybrown maggots hatch within 24-48 hours. Hairy protuberances on their dorsal surface are thought to aid progression and floating in a semi-liquid medium. The newly hatched larvae frequently wander for a time before burrowing into a suitable food source. Larval development requires a minimum period of 8 days, during which time the larva passes through 3 stages, eventually attaining a length of 6-mm. Eggs hatch after 1 to 4 days. Each larval instar lasts 3 to 5 days. Pupae leave the semi-liquid or liquid substrate for somewhat drier places to pupate.

 

Lesser house flies are more reluctant to enter homes than are house flies: instead they tend to congregate in outdoor locations especially in shaded areas. They seldom land and are not considered a significant disease vector. Strong air currents tend to disperse the male aggregations. As temperatures decline, they seek cover in buildings or protective vegetation. As temperatures rise in late spring and early summer, populations of Fannia diminish. In some parts of California Fannia are the main pest flies from November to June, with Musca domestic assuming major pest status between June and November.

 

The Lesser housefly makes longer flights and spends less time resting than the housefly. Females of the species tend to remain near the breeding sites and only the males migrate. For these reasons F. canicularis is less prone to transmit disease than M.domestica, but large populations and similar feeding habits mean that this insect, too, has a considerable potential to act as a vector of disease. It has occasionally been implicated as a vector of intestinal or urinary myiasis.

 

Flies have rapid, prolific breeding habits and high mobility. In order to break the lifecycle, control measures should be directed against larval and adult flies. Domestic refuse must be stored in well sealed bins, for early removal to disposal sites. High-risk material should be sealed in bags wherever possible. Refuse piles should be covered with earth, to a depth of at least 230 mm (9 inches), and then compacted. This will minimize larval emergence and promote fermentation temperatures at which larvae cannot survive. Farm manure should be kept as dry as possible, especially in poultry houses, where leaking water feeders can provide ideal, moist breeding conditions. The Biothermic method of storing dung involves compacting manure into a cuboids stack, a method particularly suited to horse manure. This form of storage promotes uniform, persistent fermentation throughout the dung, which is lethal to larvae. Tarpaulins can also be used to cover heaps.

 

Stable Fly, Stomoxys calcitrans. Both male and female stable flies feed on blood and are persistent feeders that cause significant irritation to host animals. Adults are 1/4 to 1/3 inch long and resemble house flies. A "checkerboard" appearance on the top of the abdomen and the stiletto-like proboscis separate this species from adult house flies. 

 

  An adult stable fly with bayonet-shaped mouthparts. 

Females deposit clusters of eggs containing up to 50 eggs. Several egg clusters may be deposited during the life of a female fly and a single female can lay up to a thousand eggs during her lifetime. The larvae have a typical maggot shape and are similar to the house fly. There are three larval stages. The last stage larva is about 2/5 inch long and is a cream white color. After the third stage larva completes feeding, it shortens, hardens and darkens in color. The chestnut brown pupa is 1/4 inch long. Stable fly pupae are very similar in appearance to house fly pupae and are difficult to distinguish since, in their natural habitat, they are usually mixed with house fly pupae.

 

They are common called the biting house fly.  Individual flies may feed more than once per day with peaks of feeding activity commonly occur during the early morning and again in the late afternoon. They prefer feeding on lower parts of the hosts such as the legs and belly of horses and cattle. On dog a common feeding location is on the nose. Both male and female flies feed on blood with the female requiring blood meals to produce viable eggs. Eggs are deposited into a variety of decaying animal and plant wastes but are rarely found in fresh manure. Fly larvae develop in excrement mixed with straw, soil, silage or grain but are also found in wet straw, hay, grass clippings, other post-harvest refuse, and poorly managed compost piles. Large round hay or straw bales, where contacted by moist soil, may also serve as a larval development site. Larval development requires 11 to 21 days, depending on environmental conditions. Mature larvae then crawl to drier areas to pupate. The pupal period varies from six to 26 days depending on temperature. The entire life cycle from egg to adult is generally completed in three to six weeks.

Stable flies prefer to feed outdoors and rarely are found feeding or resting indoors. These flies are strong fliers and dispersion from one livestock facility to the next is common. They remain active into October or later in warmer areas of the US. However, larval development slows as autumn temperatures decrease. At temperatures near freezing, larvae can survive but continue to develop slowly in habitats such as piled silage or manure where fermentation generates heat.

Stable Fly Management. A sound sanitation program is of paramount importance to fly control; all other types of control are doomed to failure without this important first step. Control of stable flies in barnyards, stables or corral areas usually involves several methods. These methods also apply for the house fly. Chemical control directed at larval and adult stages of both insects is usually required periodically during the fly season.

The basic aim of a sanitation program is to reduce or eliminate larval development sites. A number of areas require attention because of the varied habitats suitable for larval development of these flies. Manure management is essential in limiting fly production. Timely spreading of manure promotes drying and prevents larvae from developing. Even small areas, where manure mixes with straw, are ideal breeding sites for large numbers of both stable and house flies. Wet areas where manure, mud and plant debris accumulate also form ideal breeding habitats for these fly species. Modifications of the drainage around corrals to reduce excess moisture can eliminate these fly production sites and make chemical control efforts much more successful.

A variety of chemical control techniques are available to the horse owner. Generally, control of adult flies using residual insecticides as surface treatments and knock-down sprays to kill existing adult flies are the most effective techniques. Applications of residual insecticides to premises are frequently used to control both house and stable flies. Longer residual insecticides provide control for an extended period when sprayed onto sites where the adult flies congregate. Sides of buildings, inside and outside surfaces of stalls and fences may be potential day or night resting sites for these flies. Observation of your own barnyard situation will quickly tell you the favored resting sites for flies. Flies contact the insecticide when they land on the treated surfaces.

Horn Fly. Haematbia irritans. This is the smallest of the biting muscids, gray in color, approximately ³⁄₁₆ inch in length. Both the male and female have slender, black, piercing mouthparts which project forward from the bottom of the head. They often aggregate densely on cattle, each fly oriented with its head in the same direction as hair tips of that site on the host. Horn flies typically have eyes that are dark reddish-brown.

Haematobia irritans is not native to the U.S. and originally came from Europe. It can live in any similarly climatized area, as evidenced by its most recent spread to Argentina and Uruguay. In the U.S., the active time of the horn fly is between April and October and, in a warm fall, even as late as mid-November. The flies are often most abundant from June through mid-July with a second population peak in mid-to-late August.

 

                                                                       

 

                                                                                        Horn Flies on Horse. Image Courtesy USDA-ARS.

 

The horn fly lays eggs in fresh cow manure, and the female is known to laying her eggs in the feces before the cow has even completed defecation. The larvae remain in fresh pats of the animal's dung and feed on the both the resident bacterium and the compositions of the decomposition products of the resident bacterium.

The adult, on finding a suitable host, remain on it and others in the same herd for life, with the female only leaving to lay her eggs. Horn flies will also move around to different areas on the same animal to regulate their temperature and minimize their exposure to the wind. Both the male and the female subsist completely on blood, using their sharp mouthparts to pierce the animal's hide to suck it out. Males typically feed around 20 times and females around 40 times daily, and when not feeding they tend to rest around the horn region of the host.  If left untreated, horn fly numbers may reach several hundred per animal by late July or early August. At this level, cattle will usually bunch, fail to graze properly and expend considerable energy in tail switching, head throwing and stamping in an attempt to dislodge flies. High numbers (over 200) of horn flies may reduce weaning weights, because of reduced cow milk production, yearling weights and cow body condition scores. The degree of loss is associated with quantity and quality of forage available and climate. Hot, dry weather and horn fly stresses seem to be synergistic. Weight losses ranged from an average of 22 pounds per calf on a hot, dry year to three pounds on a cool, wet year with an average reduction of 11 pounds per calf over a 10-year study period. At elevations of over 6500 feet, horn fly populations may not surpass 200 per animal, and therefore, are non-economic. If the host is infested with a large number of flies, the resulting skin irritation and wounds may result in the drawing of a secondary infestation of myasis producing flies. There is some controversy over whether the horn fly is a disease vector, with at least one source asserting that the flies can be an intermediate host of Stephanofilaria stilesi, a parasite of cattle in North America. Primarily livestock (specifically cattle) but is known to feed on horses, sheep and goats to a lesser extent. The horn fly is known as a strong flier, and upon emerging as adults they can fly up to 10 miles to find a host. However, most often a horn fly will not have to fly more than three miles to find a host.

Much has been done over the years in the effort to manage, reduce, and eliminate the horn fly. Traditional methods were through the use of pour-ons, backrubbers and face powder bags, with products such as Co-Ral which is available as dust for face/horn flies. Self-applicator methods such as dust bags and backrubbers are used mainly for range or pasture herds, and are placed so that the animal cannot avoid coming into contact with it, such as at a gate through which animals pass. More recently, control of the horn fly by using ear tags on cattle has been extremely successful. The ear tags are made of a PVC matrix impregnated with pyrethroid, and can be effective for between 16 to 24 weeks. Originally, the ear tags were developed and used against such pests as ticks and by 1983 50% of cattle had ear tags. Long periods of such dosing resulted in the elimination of 95-99% of susceptible flies, but this strong selection pressure ended up resulting in the development of resistant strains of the flies. To combat this, the use of organophosphates and piperonyl butoxide as a synergist are now recommended to be alternated with pyrethroid to help slow resistance. In addition, methoprene in the form of sustained release bolus (a rounded mass of food or pharmaceutical preparation ready to swallow) inhibits the emergence of an adult insect from a pupal case or an insect larva from an egg for up to 7 months.

 Face Fly-Musca autunalis. The face fly is similar to the closely related house fly. Slightly larger, averaging about 7 - 8 mm long and grey in color with 4 dark stripes on the thorax, with a grey-black patterned abdomen. Like many true flies, in the males, the eyes almost touch when viewed from above.  Musca autumnalis is widespread throughout Most of Europe, Central Asia, also North India, Pakistan,China, and some parts of North Africa.

                                                                                                                                   Face Fly Adult.

It has been introduced into North America around the 1940s, and now spread to cover from Southern Canada into most temperate parts of the United States. also introduced to St Helena Island in the South Atlantic.

Adult flies will emerge from winter hibernation around March to early April. Daytime they feed on manure juices and plant sugars. On cattle and horses they feed on secretions of the facial orifices, around the eyes, mouth and nostrils. The adult flies will also feed on the host’s blood through wounds such as horse-fly bites. A larger proportion of face flies on the host will be females, as they have a higher need for protein provided by animal hosts. Night time both sexes will rest on vegetation

Females deposit eggs on fresh cow manure, and these hatch within hours post deposition. The yellowish white maggots feed on the microbialflora and fauna of the manure and pass though three larval stages (instars), growing to about 12 mm long. Then develop into a white pupa. They emerge as Adults approximately 10 to 20 days after egg deposit, dependent on temperature.

Musca autumnalis is considered a pest species, as it transmits eyeworm Thelazia rhodesi to cattle and horses, and in Cattle. Losses to the livestock industry are as a result of the face fly is estimated by the USDA to be $68 million annually (1979). The losses from this pest are more difficult to document than for the horn fly. However, since the fly has been implicated in the transmission of pinkeye which thus makes it a serious pest.

The face fly is not a blood sucker since its mouthparts are the sponging type like those of the house fly. The face fly feeds on various animal secretions. Tears, saliva, nasal mucus, blood and serum exuding from wounds, perspiration and filth adhering to the animal hair are all attractive to the face fly for feeding purposes. The persistence and habit of the fly in congregating about the eyes and nose of an animal cause the cattle to bunch and seek shade or water. These evasive actions by the cattle undoubtedly interfere with normal grazing patterns and thus cause reduced milk and weight gain production

 

The tsetse fly, Glossina spp., is well known for inhabiting tropical and sub-tropical areas of the world.  Both sexes are blood feeders and attack a wide variety of hosts.  This fly is approximately 2 times the size of the house fly and is brownish in color.  It feeds in the daylight and is attracted to movement.  The female fly gives birth to fully-grown larvae, having passed 3 larval instars inside the female’s body where they feed on a specialized milk gland.  Once released, the larva immediately pupates and develops into adults in 3 to 4 weeks.

These flies vector African sleeping sickness (Trypanosoma brucei), which is related to Chagas Disease.  This organism invades the cerebral spinal fluid and various organs of the body.  It is also a major problem in cattle and has prevented the development of this industry in certain parts of Africa.  The disease kills over 7,000 people per year.  First phase symptoms of the disease include irregular fever, enlarged glands in the neck and slow debilitation.  The second phase includes increased enlargement of the lymph glands and jerking movements.  The disease may progress into coma and eventual death.  There are strains of the trypanosome with the 'Gambian' strain being less severe and the 'Rhodesian' strain.

The disease is transmitted by the pathogen adhering to the mouthparts of the fly and completing part of the life cycle inside the gut of the insect.  The pathogens then move to the salivary glands of the insect and are injected into the new host.  G. palpali, is the principle vector of the 'Gambien' strain and inhabits the heavy forest of West Africa, commonly known as the "Congo." G. morsitan, vectors the 'Rhodesian' strain of the disease and is found in the Savannahs of Eastern Africa.  This fly prefers big game animals and humans.  Various control strategies are employed such as traps, insecticide applications, natural enemies, sterile male releases, and modification of the environment.  None have proven to be very effective.  Drug therapy, although highly toxic, is utilized as well as antibiotics.  This disease is considered by the World Health Organization (WHO) to be an epidemic in Central Africa with 20,000 new cases being reported a year.

 

FAMILY-TACHINIDAE-TACHINID FLIES

Tachinidae is a large and rather variable family with more than 8,200 known species and many more to be discovered. There are over 1300 species in North America. They occur in almost all habitats all over the world. There are Neotropical, Nearctic,Afrotropical^[1], Palaearctic, Oriental, Australasian and Oceanic species. This is the second largest family of flies with many economically important species.  Many are black to grey in color with an abundance of hairs and spines covering the body (Figure 216).  Tachinid flies are characteristically very active flies flying rapidly and can frequently be seen rapidly waking over the soil or on plants searching for a host.  Most species are host specific parasites of other insects and other arthropods.  They are one of the most valuable groups of insects in the biological control of pests.  The larvae of these flies are internal parasites of many different kinds of insects including Orthoptera, Hemiptera, Coleoptera, Hymenoptera and especially Lepidoptera

Adult Tachinid Fly.http://commons.wikimedia.org/wiki/User:Viridiflavus

 

FANMILY-TEPHRITIDAE-FRUIT FLIES

This is a relatively large family of medium to small sized flies with many economically important species.  Most species have picture wings (patterned coloration-spots or stripes) which they characteristically pump (move up and down) when at rest.  There are a number of economically important species that are well established in the US including the walnut husk fly, cherry fruit fly and apple maggot.  There are also a number of very important species that are not well-established in the US but are of considerable concern because of their potential to become established.  The more important of these include the Mexican Fruit fly, Oriental fruit fly and Mediterranean fruit fly.  The larvae of all of these are internal borers of fruit.    

Fruit Fly Pest Not Establish in the US.

Mediterranean Fruit Fly. This the most notorious of the fruit flies. The possible establishment of this and other exotic fruit flies in California or other states creates an enormous threat to agriculture.  Fruit flies are primary pests because they attack fruit instead of leaves, stems or roots of crops (the parts of the crop that aren’t harvested).  This is compounded by the fact that they are capable of attacking many different types of crops; the Medfly has over 200 known hosts.  Their reproductive capacity is tremendous, much like that of the housefly.  Consequently, once established, their population would explode—with heavy infestations quite likely.

 

 

  Mediterranean fruit fly.

 

Much of our fruit is sold abroad at a premium price.  If this fly became established in the continental U. S. these countries may imposed a quarantine on this fruit not wanting this fly to gain entry in their countries. With this in mind, the California Department of Agriculture has a rather extensive program to prevent these pests from becoming established in the state.  The initial phase of the program consists of attempts to prevent the accidental introduction of fruit flies.  Any foreign produce, which might contain fruit fly maggots, is inspected closely and/or quarantined.  This includes not only commercial produce, but also accidental introduction by individuals traveling.  People found carrying undeclared fruit in their luggage upon returning from a country where fruit flies occur (most tropical countries) would face an automatic fine.  U.S. Customs has rather refined inspection procedures for detecting infested fruit and are diligent in enforcing these regulations. One of these tools includes the use of beagles that have been trained to sniff our luggage containing fruit (the beagle brigade).  X-ray machines are used to search suspected luggage.

 

The second phase of the fruit fly prevention program consists of detection of initial infestations.  This is accomplished mainly by the use of traps baited with pheromone-like chemicals attractive to the adult flies.  Thousands of these traps are placed at strategic locations around the state in the attempt to detect an initial infestation before it becomes widespread.  Common locations for trap placement are around airports and throughout the community in the trees of individual homeowners--especially when fruit trees are on the premises.

 

Once an initial infestation is found and its borders are established, eradication attempts are initiated.  Quarantine borders are quickly established around the infestation in the attempt to prevent the spread of flies by either commercial or private movement of infested fruit.  Signs are posted on freeways and other streets to indicate zones of infested areas and to announce that fruit cannot legally be transported from those areas.

 

In the 1980’s, a Medlfy infestation spread over several counties of Southern California.  The primary means of eradication consisted of malathion bait sprayed by helicopters.  The spray consisted of a small amount of malathion mixed with corn syrup and egg whites, which serve as a feeding attractant to the adult flies.  This material was applied at the rate of two ounces per acre over a large geographical area.  Sprays were applied at night; this alone upset many homeowners as the helicopters only flew a few hundred yards off the ground and were quite noisy (Vietnam flashbacks). Also, there were many complaints associated with the formulation, including poisonings and a variety of ill effects on humans; these included skin irritations, nausea and headaches.  Many people were very concerned about the possible long-term effect of malathion exposure.  However, almost all these complaints proved to be unfounded.  Malathion has been used for over 30 years as a backyard spray and for a variety of other uses and has an excellent record as being a relatively ‘safe’ pesticide.  When formulated as a bait spray, malathion is about as toxic to humans as laundry detergent.  It should be mentioned that some individuals did experience a temporary nausea immediately after the helicopter applications of this material.  It is well documented that malathion bait-spray did cause mild etching on certain types of automobile paint; consequently, homeowners were advised to cover their cars on nights when applications were scheduled.

 

An alternative to a malathion bait spraying is the sterile male technique.  This consists of raising huge numbers of Medflies in a laboratory.  The male pupae are exposed to cobalt 60 gamma radiation.  As a result of this exposure, at least one dominant lethal mutation develops in the genes of the sperm in the developing pupa’s testes.  The basic concept is to release huge number of sterile males in the infested area; this greatly decreases the chance of a "natural" male mating with a naturally occurring female--thus maximizing the chance that the females will mate with sterile males instead.  If this occurs, females will not be able to produce offspring due to the dominant lethal gene carried by the sterilized males' sperm.  Releases are weekly and eventually the sterile-male-to-natural-male ratio increases.  This decreases the chance that a natural male will mate with a natural female; eventually the species is eradicated.  This technique has proven to be very effective.

 

It was not possible to use it as an alternative to the bait-spraying program in 1990 because, at the time, the initial infestation was widespread and there were not enough sterile males available to be effective.  Since that time the USDA has established a huge sterile male rearing laboratory in Hawaii.

 

Frequently bait-spray treatments and sterile male release programs are used together.  Initially the natural population may be reduced with several applications of bait-spray thus insuring a high sterile-male-to-natural-male ratio with follow up release of irradiated males.

export of many fruit crops in California if it were allowed to become established. The combined 2007 gross value of those hosts attacked by this fly was over $2.8 billion.  In the U.S., populations of this pest are found in extreme south Texas along the lower Rio Grande Valley, but are currently under eradication both there and in the bordering areas of Mexico. It has been discovered and eradicated successfully in California numerous times, with the first eradication occurring in 1954 in San Diego County.

 

Mexican Fruitfly-Anastreps ludens.  This fly is common throughout much of Central America.  We export of many fruit crops from these countries and if it were allowed to become established in California this would be a major problem. The combined 2007 gross value of those hosts attacked by this fly was over $2.8 billion.  In the U.S., populations of this pest are found in extreme south Texas along the lower Rio Grande Valley, but are currently under eradication both there and in the bordering areas of Mexico. It has been discovered and eradicated successfully in California numerous times, with the first eradication occurring in 1954 in San Diego County.

 

 

Mexican Fruit Fly-Anastrepha ludens. Image courtesy USDA-ARS.

 

Females lay eggs in groups of up to 18 and a single fly may lay several thousand eggs in her lifetime. Larvae may require 11 days to over a month to complete development, depending on temperature. At maturity, the larvae exit the fruit and burrow into the soil to pupate. Adults emerge from 12 to 100 days later depending on temperature.  Breeding is continuous with four to six generations a year.

 

ERADICATION PROGRAM. Protecting California’s environment from invasive species is the goal, and eradication via sterile insect technique (SIT) and ground treatments is the strategy. SIT relies on a continuous release of thousands of sterile Mexican fruit flies per square mile each week. When the sterile males mate with wild females, no offspring are produced and the wild fly population becomes extinct.

 

Sterile fruit flies will be released each week for at least two life cycles beyond the last fly find. If there is evidence that a breeding population exists in an area, supplemental ground treatments may be required to mitigate the spread of MFF. In this case, host trees and plants within a 200-meter radius of the find site are treated with a handheld hose that dispenses an organic formulation of Spinosad. Treatments are repeated every seven days for six weeks or for one life cycle. If larvae are discovered, fruit from the infested property and up to 100-meters around the find site may be removed and taken for disposal under regulatory compliance.

 

Oriental Fruitfly- Bactrocera dorsalis The oriental fruit fly is widespread throughout much of Pakistan, India, Sri Lanka, Sikkim, Myanmar, Indonesia (Celebes, Borneo, Sumatra, Java), Malaya, Thailand, Cambodia, Laos, Vietnam, southern China, Taiwan, Philippine Islands, Micronesia, and Mariana Islands (Guam, Rota, Saipan, Tinian). In the U.S. it is currently present on all major Hawaiian Islands after being accidentally introduced into Hawaii in 1944 or 1945 (Mau 2007).

 

 

Adult Oriental Fruitfly.  Image courtesy USDA.

 

Adult Identification. The adult, which is noticeably larger than a house fly, has a body length of about 8.0 mm; the wing is about 7.3 mm in length and is mostly hyaline. The color of the fly is very variable, but there are prominent yellow and dark brown to black markings on the thorax. Generally, the abdomen has two horizontal black stripes and a longitudinal median stripe extending from the base of the third segment to the apex of the abdomen. These markings may form a T-shaped pattern, but the pattern varies considerably. The ovipositor is very slender and sharply pointed

Four major oriental fruit fly infestations in California were eradicated between 1960 and 1997. A new infestation of this pest was detected in San Bernardino County, California, in August 2002. In 2004, the USDA quarantined a portion of San Bernardino and Orange counties in California. Regulatory activities in those counties ceased in December 2006 and July 2007 respectively. Several other counties in central and southern California also reported finds during 2007 (CDFA 2008).While not established in Florida, oriental fruit flies are occasionally trapped in this state.

Development from egg to adult under summer conditions requires about 16 days. The mature larva emerges from the fruit, drops to the ground, and forms a tan to dark brown puparium. Pupation occurs in the soil. About nine days are required for attainment of sexual maturity after the adult fly emerges. The developmental periods may be extended considerably by cool weather. Under optimum conditions, a female can lay more than 3,000 eggs during her lifetime, but under field conditions from 1,200 to 1,500 eggs per female is considered to be the usual production. Apparently, ripe fruit are preferred for oviposition, but immature ones may be attacked also.

The oriental fruit fly has been recorded from more than 150 kinds of fruit and vegetables, including citrus, guava, mango, papaya, avocado, banana, loquat, tomato, surinam cherry, rose-apple, passion fruit, persimmon, pineapple, peach, pear, apricot, fig, and coffee. Avocado, mango, and papaya are the most commonly attacked.

 

Injury to fruit, as with other members of this genus of fruit flies, occurs through oviposition punctures and subsequent larval development. It was introduced into the Hawaiian Islands about 1945, apparently by U.S. military troops returning to the islands. Once there, the oriental fruit fly soon became a more injurious species than the Mediterranean fruit fly or the melon fly before it was partially brought under control by introduced parasitoids.

In Hawaii, larvae have been found in more than 125 kinds of hosts. Infestations of 50 to 80% have been recorded in pear, peach, apricot, fig, and other fruits in West Pakistan. It is the principal pest of mangoes in the Philippines. It was a serious pest of citrus and other subtropical fruits in Japan, Okinawa, and the Japanese islands of Amami, Miyako, and Bonin before it was eradicated. All Japanese territories were declared free of the oriental fruit fly in 1985, after an 18-year program of eradication combining insecticide-impregnated fiber blocks or cotton containing the powerful male attractant methyl-eugenol, and the sterile insect (sterile male) technique. Steiner traps baited with a lure and toxicant are also used to monitor the presence and control of the flies.

This pest has been intercepted on many occasions at ports of entry on the U.S. mainland. The extensive damage caused by the oriental fruit fly in areas similar to Florida indicates that this species could rapidly become a very serious pest of citrus and other fruit and vegetables if it became established in Florida. USDA-APHIS, in cooperation with threatened states, has established action plans that go into effect when fruit flies are trapped and reported (USDA 2008).

 

Melon Fly-Bactrocera curcubitae.  This fly is a serious agricultural pest, particularly in Hawaii. The adult melon fly is 6 to 8 mm in length. Distinctive characteristics include its wing pattern, its long third antennal segment, the reddish yellow dorsum of the thorax with light yellow markings, and the yellowish head with black spots.

                                                                                                   Melon Fly Adult. Image courtesy Scott Bauer, USCA ARS

 

Development period from egg to adult ranges from 12 to 28 days. The female may lay as many as 1,000 eggs. Eggs are generally laid in cavities in young fruit, but are also deposited in the succulent stems of host plants. Once the larvae complete their development feeding inside the fruit pupation usually occurs in the soil. There may be as many as 8 to 10 generations a year.

Melon flies are most often found on low, leafy, succulent vegetation near cultivated areas. In hot weather they rest on the undersides of leaves and in shady areas. They are strong fliers and usually fly in the mornings and afternoons. They feed on the juices of decaying fruit, nectar, bird feces, and plant sap.

The melon fly is native to India, and is distributed throughout most parts of the country. It can be found throughout most of southeastern Asia, including the Mariana and Hawaiian Islands. It is the first tephritid fruit fly species established in Hawaii. It was introduced into the Hawaiian Islands from Japan around 1895, and by 1897, when it was first observed, it had already become a serious pest. It is also found in Egypt, Kenya, Tanzania, Burma, Ceylon, Formosa, Guam, Japan, Java, Kenya, Malaya, Mauritius, Philippines, Singapore, Southern China, Timor Island, Pakistan, all of southeast Asia as far north as Nepal and on the islands of New Guinea and Taiwan.

Although a single specimen was collected in 1956 in Los Angeles County, California, it is not yet established in the continental . Plant quarantine inspectors at west coast ports of entry have made many interceptions from Hawaii.

Melon flies use at least 125 host plants. They are major pests of beans, bitter melon, winter melon, cucumbers, eggplant, green beans, hyotan,luffa, melons, peppers, pumpkins, squashes, togan, tomatoes, watermelon, and zucchini. In the Indo-Malayan region, the melon fly is considered the most destructive pest of melons and other related crops. In Hawaii, it has caused serious damaged to melon, cucumber and tomato crops.

The melon fly can attack both flowers, stem and root tissue, and fruit. The two most common mechanical methods of control are wrapping developing fruit with a protective covering and the use of baited trap. The most effective cultural management technique is the destruction of all infested and unmarketable fruit, and the disposal of crop residues immediately after harvest.

                                                                                               Domestic Fruit Fly Pests 

 

Walnut Husk Fly, Rhagoletis complete. This fly infests walnuts in most California walnut-growing areas. It feeds on black walnut and on all varieties of English walnut, but some early maturing varieties can escape infestations in most years. The walnut husk fly is about the size of a housefly and very colorful. It has a yellow spot just below the areas where the wings are attached and iridescent, greenish eyes. The wings have three prominent dark bands, one of which extends around the wing to form a V-shape. The banded wings distinguish it from other flies found in the walnut orchard.

Larvae feed in groups within the husk, but you won’t see them unless you remove the skin of the damaged husk. Dark, soft blotches on maturing husks are a good clue to husk fly presence. Blotches that are hard and dry are caused by blight disease and should not be confused with husk fly damage.

Adult Walnut Husk Fly. http://www.entomart.be/listetotale.html.

Life Cycle. This fly has one generation per year. Walnut husk flies overwinter as pupae in the soil and emerge as adults in some areas as early as May but generally around July 1. Peak emergence often occurs mid-July through mid-August. The female fly deposits eggs in groups of about 15 below the surface of the husk. Usually the first sign of an infestation is a small, sting-like mark on the husk caused by this depositing of eggs. At first these areas are difficult to see, but they soon darken and appear as little, black spots on the husk, usually near the stem end of the husk and often on the shaded side of the nut. Eggs hatch into white maggots within 5 days. The maggots feed inside the husk, enlarging the black area, which remains soft, unsunken, and smooth. The outer skin of the husk usually remains intact, but its fleshy parts decay and stain the nutshell. Older maggots are about 1/4 inch long and are yellow with black mouthparts. After feeding on the husk for 3 to 5 weeks, mature maggots drop to the ground and burrow several inches into the soil to pupate. Most emerge as adults the following summer, but some remain in the soil for 2 or more years.

The primary damage from the husk fly is nutshell staining, which is a problem in commercial orchards where nuts are grown for in-shell sale; however, this can be tolerated in backyard situations. Feeding by the husk fly maggots also causes the damaged husks to stick to the shell, making them difficult to remove. An early season husk fly infestation (June to mid-August) can result in shriveled, moldy kernels.

Control. Most home growers ignore the walnut husk fly, because generally it doesn’t affect the nutmeats. Since the husks can be difficult to remove, home growers can place the damaged nuts in a damp burlap bag for a few days before attempting to remove the hull. Be sure to dispose of infested husks in a tightly sealed bag. Certain general sanitation practices that reduce the number of husk flies overwintering near a tree or orchard can assist with control. These practices include removing and disposing of damaged nuts as soon as possible. It also might be possible to reduce next year’s population by spreading a tarp under the tree from July through August to prevent the maggots from entering the soil to pupate.

If gardeners feel treatment is necessary in home orchard situations for trees with early or severe infestations, they can make multiple applications of insecticide combined with bait beginning in July. These sprays are aimed at controlling adults before they can lay eggs. Spray on a 7- to 14-day interval until within 1 month of harvest. Eggs laid later than this will not have time to develop and cause damage.

Add bait to the spray as an attractant so that the flies will feed on the spray. When using bait, complete coverage of the tree often is not required.  This makes application easier for home gardeners with large trees. Commercial growers use specially prepared baits that they mix with insecticide or pre-mixed insecticide baits for walnut husk fly such as GF-120 Naturalyte Fruit Fly Bait. These products are sold only in large quantities but sometimes are available at farm chemical suppliers for home use. Their effectiveness for home use situations is unknown.

Olive Fruit Fly- Bactrocera oleae.  Until 1998, the fly had not been detected in the United States, and its range coincided with the range of the olive tree in the Eastern Hemisphere: northern, eastern and southern Africa, Canary Islands, India, Western Asia. In the Western Hemisphere, it is currently restricted to California.  The olive fruit fly was first detected in North America infesting olive fruits on landscape trees in Los Angeles County in November 1998. It can now be found throughout the state.  Its likely source of importation was from France.

 

The olive fruit fly is one of the smaller species in the genus. The adult female is approximately 5 mm long, and has a wing expanse of approximately 10 mm. The wings are mostly transparent and marked with brown, including a spot at the wing tips. The thorax is black, with a silvery pubescence dorsal surface stripped with three narrow parallel black lines. The humeri, or shoulders, and an area above and below the base of the wings are yellow. The inner portion of the scutellum is black, and the posterior portion is yellow. The abdomen is black, covered with a scattered gray pubescence. The basal segments are marked with pale transverse bands and an irregular parallel bar or blotch of reddish-brown occupying the center of the apical segments. The terminal segment is reddish-yellow.

 

                                                                                        

 

                                                                                     Olive Fruit Fly.  http://commons.wikimedia.org/wiki/User:Alvesgaspar

 

The life cycle of the olive fruit fly is closely linked to the seasonal development of its main host, the cultivated olive (Olea europea), and to the local climate. In mild coastal areas of California, adult flies remain active year-round, and the eggs and maggots can be found throughout the year in fruit left on the ground or on the trees.

In inland areas of California, adult flies emerge from March to May and attack olives remaining on trees from the previous season. During early summer (June) as temperatures and day length increase and few mature fruit remain on trees, female flies do not lay eggs. Although few olives are present from the previous crop to host the egg laying, the adults remain active, and they may disperse to new locations such as citrus orchards or vineyards.

By late June to the beginning of July as the new olive crop develops, females begin to lay eggs and are attracted to the fruit. Although eggs may be laid in small fruit, the larvae do not successfully develop until the ripening fruit grows to sufficient size. Eggs are laid just under the fruit’s skin.

In the Eastern Hemisphere, insecticides are used in bait-sprays or as sprays from the air to control the olive fruit fly. More environmentally benign techniques that are being tested or used in limited areas are use of radiation sterilized males and pheromones. Both sexes can be sterilized with 8 to 12 krad (80 to 120 Gy radiation) when late pupae are exposed to the irradiation. Synthesis of 1,5,7-trioxaspiro[5.5]undecane, an analog of the major pheromone component, has been synthesized and tested, and under optimal conditions it was as attractive as the natural compound, but it did not last as long in traps as the natural material. Small plywood rectangles dipped in 0.1% (a.i.) aqueous solution of deltamethrin for 15 minutes and added to bait stations containing either sex pheromone or ammonium bicarbonate, a food attractant, gave cost-effective control in a large test orchard.

In California, management depends on bait sprays, trapping of adult flies, harvest timing, fruit sanitation after harvest, and biological control .A recent (2008) introduction of a hymenopteran parasitoid, Psyttalia cf. concolor, from Kenya has raised hopes for effective biological control of the olive fruit fly. The wasp appears to be a more effective natural enemy than other olive fly parasitoids brought to California in the early 2000s. Early results showed that the wasp's parasitism rate was variable in some hot, dry, inland groves, where the olive fruit fly is sparse, but in a coastal orchard heavily infested with the flies, parasitism was very high. 

Apple Maggot-Rhagoletis pomonella.  This fly (also known as the "railroad worm") is an insect native to North America. Originally it fed in the fruit of wild hawthorn (Crataegus spp.), but then it became a primary pest of cultivated apples, especially in the northeastern United States and southeastern Canada. Summer- and early fall-maturing varieties are particularly vulnerable, but hard winter apples are sometimes infested. Thin skinned sweet and subacid varieties are most susceptible, but acid varieties may be attacked. Plum, pear, and cherries also serve as hosts, but usually the apple maggot is not a serious pest of these fruits. Crab apples are invariably infested by this pest. A closely related species, the blueberry maggot fly (Rhagoletis mendax Curran), is important as a pest of cultivated blueberries.

 

Rhagoletis pomonella is a pest across eastern North America from eastern North Dakota and southern Manitoba to Nova Scotia, southward to eastern Texas to central Florida, occurring over the entire middle and eastern region of the United States. In 1981 it became established in Oregon, from where it spread to California, Washington State, Utah and Colorado, and eventually Nebraska in 1991.

 

Adults of the apple maggot are slightly smaller than a house fly, black in color, with white bands on the abdomen (four on the female and three on the male), and the wings are conspicuously marked with four oblique black bands.

 

                                                                                   

 

Apple Maggotc.  Image Courtesy USDA.

 

Larvae are white or yellowish tapered maggots slightly smaller than those of the house fly. The maggots are about 1/2 inch in length and tapering toward the head.
Adults emerge from the ground during early summer. Emergence continues for a month or more, and many pupae may remain inactive and not emerge until the second year. Egg-laying usually does not take place until eight to 10 days after the flies have emerged. The female punctures the skin of the fruit with her ovipositor and lays eggs singly in the pulp. Eggs hatch in five to 10 days. The maggots develop slowly in the green fruit and usually do not complete their growth until the infested fruits have dropped from the tree, after which growth is completed rapidly.

Larval development requires from two weeks in drops of early maturing apples to three or more months in hard winter varieties. Then the larvae leave the fruit and enter the soil where the puparia are formed. R. pomonella undergoes a partial second generation in the southern part of the range, with adults emerging in early fall. Winter is passed as puparia in the soil.

The maggots bore throughout the fruit, forming irregular, winding tunnels which turn brown, often causing premature dropping of fruit. When the fruit is slightly infested, there may be no external indication of the presence of the maggots, but when the fruit ripens, the burrows show as dark, winding trails beneath the skin. Minute egg punctures and distorted, pitted areas may show on the surface. Heavily infested early varieties of fruit will be reduced to a brown rotten mass filled with the fly larvae.

 

 

Damage from Apple Maggot.  Image Courtesy Whitney Cranshaw,

 

Control.  The systematic destruction of infested apples and the elimination of hawthorn and abandoned apple trees in the vicinity of orchards are considered valid control practices. Apple maggots in fruits may be killed by placing the fruit in cold storage at 32°F for a period of 40 days.

Consult local university or state recommendations or registered chemicals. Emergence and dispersal of adult flies must be carefully monitored to effectively time treatments. Sticky traps, including yellow rectangles and red spheres, are used in other areas to monitor adults and time treatments. Unfortunately, only provisional economic thresholds are available for apple maggots, even in areas where it has long been a pest. The first emergence of adults can be detected by hanging yellow sticky traps in abandoned orchards or unsprayed apple trees in infested areas. To detect the beginning of egg laying, red sticky spheres are hung in apple trees; once detected applications should commenced immediately.

  55. Syrphid fly adults and larvae typically feed on aphids and other soft bodied insects.  The adults are typically bee-like in appearance.

  56. Most experts feel that malation bait spray is about as toxic to humans as laundry detergent.

  57. Exposure of male Medfly pupae to Cobalt 60 (at the proper dosage) will result in at least one dominant lethal mutation in the genes of developing sperm.

  58. Adults of long legged flies and robber flies are both predatory.  Long legged flies are more important from the standpoint of biological control in cropping situations.

  59. The tachinid flies are extremely important from the standpoint of biological control.

  60. Some species of blow flies deposit their eggs in wounds of living animals.  The feeding of blow fly larvae in wounds in some cases is considered beneficial to the host animal.

  61. Flesh fly larvae have similar feeding behaviors as blowflies.  That is they typically feed in meat, flesh and the like. 

  62. Adults of flesh flies are typically larger than house flies, with a grey and black checkered abdomen.

  63. The stable fly is a fly that is very similar in appearance to the house fly; one primary difference is that the adults are capable of delivering a painful bite and feed on blood resulting

        from their bite.