Images Dr. Kaae.
Cockroaches are a very successful group of insects with fossil records dating back at least 280 million years. They have flat oval bodies, elongate antennae and heads held so as not to be visible from above. Their front wings are leathery (tegmina) and may be well-developed (macropterous), short (brachypterous) or lacking (apterous). In many species, the female's front wings are shorter than the male's. Most common species deposit their eggs in cases called ootheca. Depending on the species, there may be anywhere from 16 to 64 eggs in each case. Cockroaches are mainly tropical in distribution with most species in the United States found in the southern states.
Cockroaches are some of the most successful organisms on the earth. There are many factors that lead to this success. Even though these insects have 6 legs, they typically only move three at a time. The first and third leg on one side and middle leg on the other side move in unison while the other 3 remaining stationary forming a tripod. Once the moving legs touch the ground, they in turn form the tripod and then the remaining move in unison. Of course this process provides the roach a degree of stability even when running. As a result, roaches can instantly stop in a dead run without falling-a phenomenon rarely if ever seen in other animals. Walking roaches can break into a run by merely increasing the pace of the indicated sequence. It is well-documented that roaches are one of the fastest running animals based on a proportional scale. The American cockroach has been clocked at a speed of 50 body lengths per second. That is approximately 10 times faster than the fastest human can run and 3 times the relative speed of a cheetah. On a relative scale (body length compared actually speed), this computes to almost 150 miles per hour. In order to achieve a maximum speed, some species will spread their front wings, thus (leathery tegmina) moving their center of gravid backward and allowing the roach to run on its hind legs.
Cockroaches possess subgenera organs that are located at joints on the legs and function to detect the slightest sound including the movement of the legs of other roaches. The tip of each leg is suited with a pair of hook-like structures (tarsal claws) and sticky pads which allow these creatures to crawl up (and even upside down) on most surfaces. Roaches are more than capable of walking upside down on a glass surface.
A pair of anal cerci is located on the tip of the abdomen. These peg-like structures serve to detect vibrations. A roach may place them on the ground or hold them in the air and readily detect approaching danger. As a kid I used to work in one of the snack bars in Huntington Beach State Park. We had a massive German cockroach infestation for the 8 years I worked there. You would pick up a box of candy bars and 50 roaches would run out. You could come in at night and turn the light on, and the floor would seem to part. If you came in and did not turn the lights on, but tapped the floor with your foot, the floor would still appear to part due to running roaches. They could detect the air movement created by opening the door or ground vibration from the tapping foot. After 8 year, a pest control operator was finally called in.
One of the significant internal organs attributing to cockroach success is their nervous system. A roach is truly a beast with two brains. It has a large paired nerve ganglion in the head and a single ganglion nears the posterior of the roach. These are connected by giant fibers which carry nerve impulses 10 times faster than human nerves. Experiments indicate that a warning input from a roach anal cerci can be transmitted into leg movement in as little as 0.045 seconds (literally faster than a blink of the eye).
Left. A South American and Indian DominoCockroach with Peg-like Anal Cerci. Left Image Courtesy of Entophiles. Right Courtesy Sripathiharsha CC BY.SA 3.0
Cockroaches are nocturnal (active at night), negatively phototropic (avoid light), and positively thigmotactic (preferring to hide in areas where a surface touches both the top and bottom of the body). They hide primarily in cracks and crevices. Many species are also gregarious and are frequently found together in non-social groups. It is thought that they secrete pheromones that help them to congregate; the function of these loose groups is not totally understood.
An American Cockroach eEhibiting a Positive Thigmotactic Behavior. Image Dr. Kaae.
An added advantage is that roaches are omnivorous (feeding on all types of food). These insects will eat almost everything humans eat and much more including feces, book bindings, paper, ink, cork paste and any rotting organic matter. Cockroaches have even been found feeding under the toenails and fingernails of patients confined to hospital beds. In some ocean freighters, the roach populations are so large that crew-members sometimes wear socks and gloves to bed to prevent them from feeding underneath their fingernails and toenails.
My wife and I recently witnessed a cockroach’s ability to find and consume food. We sat down to dinner at a well-known restaurant. Right next to our table was a fairly large painting. We decided to have a glass of wine before dinner. Within minutes of arrival of the wine, a German cockroach appeared from beneath a painting on the wall and walked out to the middle of our table. Our reaction was not that of normal human beings, and we decided to give it some wine. I placed a small drop of wine several inches from the roach which immediately recognized the presence of food through its antennae (smell). It walked over to the drop and tasted it with its maxillary palps. The roach proceeded to suck up the entire drop (which wasn’t much smaller than the roach). It then crawled back to the picture and disappeared. Much to our surprise, within a few minutes the roach reappeared and came back on the table. I gave it another drop, and it repeated the entire process of smelling, tasting and consuming the wine-Chablis. Once finished, it cleaned its antennae and returned to the picture. A few minutes later, the roach dropped from the picture and began to spin on its back. Inebriated? I would think so.
GOOD ROACH-BAD ROACH
In some areas of the world, roaches could be considered beneficial. In tropical areas where these insects abound, roaches play a significant role in the recycling of decaying plant and animal matter. For example, in the Amazon a single species of forest floor roach is reported to produce over 6% of the turn-over of decaying plant material. As might be expected, these critters are extremely important in many food chains composing a significant part of the diet of carnivores such as lizards, frogs, fish, birds, salamanders, rats, mice and other small mammals. It has also been documented that in many areas of the world, some species of roaches are important as pollinators of certain rainforest plants. Because of their relatively large size and ease of rearing, roaches are the most commonly used specimens in studies of insect behavior, physiology, anatomy and morphology. Finally, some of the larger species (and even smaller ones) have become quite popular as pets in the U.S. and other countries such as Japan. A quick search of the web will reveal many sites that sell these seemingly disgusting critters.
In some situations, these insects could be considered beneficial. A recent survey conducted by the U.S. Fish and Wildlife Service indicated that cockroaches were the least favorite animal in the U.S. They are followed by mosquitoes, rats, wasps, rattlesnakes and bats. I imagine bedbugs are at the top of the list these days. With many individuals, the mere sight of a cockroach can bring on nausea. One of my recent students who was enrolled in a general education course in entomology indicated that she liked most of the pictures on the CD we used in the class, but that every time the picture of a roach appeared, she ran out of the room screaming.
This fear of roaches is without a doubt a learned response. Studies indicate that children under the age of 4 typically have no fear of roaches, but older children are typically told by their parents and peers that these critters are disgusting, vile and filthy. A personal note-our kids, grandkids and now great grandkids have had repeated exposure to a colony of Madagascar hissing cockroaches that we have maintained for years. Not one of them considers roaches to be disgusting, vile or filthy. Of course from the standpoint of a pest control operator, the fear of roaches is not a bad thing.
The role of roaches in the transmission of disease is well-studied. Studies indicate that about 40 different pathogens are naturally carried by roaches and make them possible suspects in the transmission of diseases such as polio, pneumonia, leprosy, bubonic plague, food poisoning, dysentery, typhoid fever, salmonella and infectious hepatitis, among others.
Certainly the transmission of these diseases is not limited only to roaches. Water, air, hands, flies and any of a number of other ways can also transmit such maladies. Such transmission is referred to as mechanical where there is no biological association between the pathogen and vector. In the case of roaches, transmission is quite simple. The pathogen is transferred from the source to the victim externally on the exoskeleton or parts of the insect. One of many possible scenarios could be a roach lives in a sewer and subsequently moves to human food and thus moves the pathogen from the source to the food. Another possible means of transmission is through the feeding. When roaches feed, they regurgitate partially digested food and frequently defecate near their meal. A simple scenario could be a roach feeds on feces (they seem to love it-check your dog feces in your backyard if you don’t believe it)) and then moves on to human food.
The role of roaches causing allergies or asthma is well-documented. According to the National Institute of Health, as many as 15 million Americans may suffer from roach related allergies. There is additional evidence that roach related allergies may lead to allergic reactions when consuming other arthropods such as shrimp crabs and lobsters. Such allergies are not due to the presence of insects themselves but because their bye-products such as cast skins, pheromones and feces. Typical symptoms of roach allergic reactions include rashes, runny nose (mild), labored breathing or in the most severe cases death from shock (rare). As might be expected, cockroach allergies are more commonly encountered in low-income neighborhoods (more roaches) and when families are crowded together under unsanitary conditions and in the northern areas with long cold winters where individuals remain indoors for extended periods of time.
Control of pest species is primarily with insecticides; however, proper sanitation is important in preventing cockroaches from reaching pest levels. If food is left exposed to these nocturnal feeders, their populations will increase much more rapidly than if certain precautions are followed. Dirty dishes should not be left on the sink overnight. Any accumulation of grease is especially attractive to these insects, and it is best to store food in "cockroach proof" containers whenever possible. Stored pet food should be closed off tightly, preferably in containers with tight-fitting lids. As discussed, cockroaches can feed on paste, bookbinding’s, soap, paper and other marginal "foods." However, when forced to do so, they generally develop more slowly and have a higher mortality rate. Once established, it is virtually impossible to 'starve out' an infestation. Experiments indicate that roaches can live for up to three months without food and two months without water.
Some chemical control is based on the thigmotactic behavior of these insects. Residual insecticides are applied to all cracks and crevices of an infested structure, and when roaches hide during the day, the residues kill the pests on contact. Some of the new synthetic pyrethroid insecticides are extremely toxic to roaches. For example, one month after a surface has been sprayed with some of these insecticides, a roach can die after merely running across it.
These chemicals are now readily available to homeowners. It should be noted that these chemicals are selectively toxic to insects; that is, when properly used, they have little effect on humans.
Worldwide there are about 5,000 species of which only 70 are established in the United States. These are mostly found in southern states with Florida leading the way. Cockroaches are extremely successful animals and are thought to have originated more than 280 million years ago. Most live outdoors and prefer a warm, humid environment. In California, 4 main species are commonly found indoors and become pests. These domestic species are the American cockroach (Periplanetia americana), the Oriental cockroach (Blatta orientalis), the Brown-banded cockroach (Supella longipalpa), and the German cockroach (Blatella germanica). All these species originated in the tropics and were introduced into the United States via commercial transport.
American Cockroach. This is the largest of the domestic species with adults rarely reaching 1 1/4 inches in length; it is chestnut brown with light-brown-to-yellow bands around the margin of the top of the prothorax. This species is also known as the sewer roach and commonly abounds in such locations.
Adult American Cockroach with Egg Case, Periplaneta americana. Image Dr.Kaae.
The American roach is primarily an outdoor species but may enter homes to feed. The life cycle from egg to adult may require from 1 to 2 years depending on prevailing temperatures. In addition, adults can live up a year or more. Adult females are capable of depositing 50 or more egg capsules (ootheca) which contain 16 eggs each. This is the most common species of roach found in sewers in the U.S., and they are commonly referred to as sewer roaches. It prefers higher temperatures and humidity and tends to replace the German roach as the most common roach found in homes in Asia. In the U.S., the German roach is the most common roach found in homes since it prefers lower temperatures.
Oriental Cockroach. This species is a large, shiny-black-to-reddish-brown and about 1 inch in length. This roach exhibits sexual dimorphism where males and females of a species are distinctly different in form. The females are nearly apterous with very short vestigial wings while the males are brachypterous (short wings) with the wings covering all but the last 2 abdominal segments. This species is frequently referred to as 'water bugs'. This is due to the fact that many homeowners are reluctant to admit that they have cockroaches and this roach prefers humid environments. This is primarily an outdoor species, but is common in garages and will readily enter other structures at night to feed. A prime location for Oriental cockroaches is water meter holes in alleys. These cavities are dark, humid and undisturbed. The roaches emerge at night to feed in garbage cans, ripe fruit on the ground and pet food dishes. The life cycle of the Oriental roach is quite similar to that of the American.
Left-Apterous Adult Female Oriental Cockroach. Right-Brachypterous Male. Images Dr. Kaae.
Brown-banded Cockroach. This is a smaller species which is about l/2 inch long, brown in color and distinguished by horizontal tan stripes on the base of the wings behind the prothorax. The sexes differ in that the male is longer and narrower with fully developed wings. The female is darker, broader and has shorter wings. This species primarily infests buildings and lives throughout structures.
A Male (Left) and fFmale (Right) Brown-banded Cockroach. Images Dr. Kaae.
German Cockroach. This is the primary cockroach found in homes and restaurants in the United States with approximately 90% of roach infestations in structures attributed to this species. This roach is about the same size and color as the brown-banded, but can readily be distinguished by 2 longitudinal black stripes on the dorsal side of the prothorax. In the nymphal forms, the stripes extend down onto the abdomen. The life cycles of the German and brown-banded cockroaches are similar—both species complete development in 60 to 90 days.
Adult German Cockroach Carrying Egg Case, the Most Common Species Found in the Home. Image Dr. Kaae.
The German cockroach is unique in that the female carries its ootheca protruding from the abdomen until the eggs are ready to hatch. This is to our advantage when attempting to eradicate this pest from our homes. If a female carrying an egg case is killed, the unhatched eggs also die. Apparently there is an essential contact between the mother and her eggs. Eggs of most insects are difficult to kill with pesticides. Unfortunately, the American and Oriental cockroaches randomly drop their egg cases soon after they are formed. The brown-banded cockroach attaches their egg cases behind objects, such as drawers and picture frames.
The German cockroach has a faster life-cycle and lays more eggs than any of the other common house infesting roaches. As a consequence, it tends to increase in numbers more rapidly than these other species. Under ideal conditions, this insect can produce 3 to 4 generations per year. In addition, each female can produce up to 8 ootheca containing 30 to 40 eggs each. Their reproductive capacity, and the fact that the environmental conditions that are typically found indoors are enhances their development and pest status.
A simple comparison of the potential reproductive capacity of the German and Oriental cockroach (or actually any of the other pest species) will illustrate the difference of each. A female Oriental cockroach typically produces five egg cases containing 16 eggs each and after hatching, the nymphs require a year to grow to adulthood. A simple calculation indicates (assuming 100% survival) that a mated female Oriental cockroach is capable of producing 80 adult roaches in a one-year period. On the other hand, a female German cockroach produces an average of eight egg cases containing 16 eggs each which after hatching complete development in three months. As a result, after three months one female would produce 108 adults, half of which are female. In turn, those females would produce 5832 adults in another three months. Assuming two more generations after one year, a single female German roach is capable of indirectly producing 2,576,000 offspring or over 320,870 times as many offspring as the female Oriental roach. It should be emphasized that this is a hypothetical calculation and there are many factors that greatly reduce the reproductive capacity of roaches, but it does give great insight as to why the German roach is so much more of a pest than the other domestic species.
During the 1950's and 60's, if a home was infested with German cockroaches, they were almost exclusively confined to kitchens and bathrooms. Over time, infestation gradually began to be seen in different areas of the home; today they frequently are spread throughout the structure. This apparent change in cockroach behavior can be explained by a combination of changes in human behavior and home construction since the 1950's.
German cockroaches prefer environments with high humidity, high temperature and available food. Fifty years ago the family normally sat and ate dinner and other meals together in the kitchen. Today, due to busy schedules, two-income families, and the advent of television, families rarely eat meals altogether or in the kitchen. Consequently, crumbs and other droppings are spread throughout the home and attract these roaches. Higher humidity in the 1950's was typically confined to the bathroom and kitchen. Older homes were usually built with one bathroom. However, bathrooms in newer homes frequently are found in several areas. As a consequence, there is increased humidity throughout the structure. Also, with the advent of central air conditioning, moisture tends to condense in wall voids where the cool room air meets the hotter outdoor air. Finally, there has been a tremendous increase in the number of televisions, microwave ovens, computers and other small appliances in homes; these are sources of heat that attract German roaches. Additionally, while sitting for long periods at the computer or television, we often have a little snack (or a full-blown meal). The combination of heat, high humidity and food must be irresistible to cockroaches!
German cockroaches can reach tremendous populations in a fairly short period of time if the right conditions exist. Recently, there have a number of lawsuits throughout the U.S. where tenants are suing slumlords for continuous unsanitary and run down conditions. Large rat and German cockroach infestations are a considerable part of the problem.
We recently visited one of these heavily infested complexes in Los Angeles. Upon entering one of the units, dozens of roaches were sitting or running about on the walls. This was quite unusual because it was day time and roaches, of course, are nocturnal. Normally, in structures where roaches are active during daylight hours, it is an indication of a very large infestation as they probably have run out of places to hide. The tenant indicated that conditions had become intolerable: a bowl of food could not be placed on the kitchen table without it being visited by hoards of roaches. It is not that unusual to find roaches hiding in the ears and up the noses of sleeping children. The ultimate insult was when one of the tenants was feeding her two-year-old and a roach crawled out of the child’s mouth.
Extreme Cockroach Infestation-Same Location. Left. To Right. Roaches Caught in Randomly Placed 3-inch by 2-inch Sticky Trap-one Night. Plate Full of German Roaches. Roach Feces in Kitchen Cupboard-As Bad as It Gets. Images Dr.Kaae.
If that story grosses you out, I suggest you not read the rest of this paragraph. Recently a doctor friend was examining an extremely overweight lady. She claims that she was examining an area between two flaps of fat on the patient's arm and she first found cookie crumbs and then a few German cockroaches living in this and several other areas of the woman’s body. The doctor was repelled by the finding and required the patient to take a shower before continuing the examination. Although I am sure this is exceedingly rare, it does make biological sense. Such a situation meets all of the biological requirements for this species: food, heat, high humidity and a thigmotactic location.
Madagascar Hissing Cockroach. This roach is an African species that has gained considerable notoriety due to its use in a number of movies (e.g. Damnation Alley, Indiana Jones and the Temple of Doom, and Men in Black). Adults may approach three inches in length and are capable of producing a hissing sound when disturbed. Contracting the body and expelling air out the trachea (internal breathing tubes) through the slit-like openings of these tubes to the outside produces this noise. This hiss mimics that of a snake and is a startle-defensive mechanism possibly used to ward off attacking predators. Male roaches also use hissing while mock fighting over females. Males can easily be distinguished from females by the presence of two small projections on the prothorax.
Left. Male Madagascar Hissing Cockroach with Hornlike Projections on Top of Prothorax. Right-Female. Images Dr. Kaae.
The effectiveness of this defensive mechanism was recently documented in our own home. I brought a box of hissing roaches home from school several years ago. They escaped by pushing open the lid of the box. I assured my wife that they were a tropical species and would not survive in our home. I was proven wrong two years later when we turned over our round oak table and there was a mother and her babies living in the hollow pedestal. Since then, one summer night a loud hissing in the front room wakened us. Upon inspection, our cat was sneaking up on a large roach, only to jump a few feet in the air after the pounce of the cat and resultant hiss of a Madagascar roach.
Finally male roaches apparently stimulate female to mate with their hiss. In one experiment, the spiracles of male roaches were sealed preventing the ability to hiss. When placed with females, these individuals were no longer attractive to females until the sound of hissing roaches was reproduced with a tape player.
Rhinoceros Cockroach. This is certainly one of the largest species of cockroaches in the world-perhaps the largest. Their distribution is limited to northern Queensland and reaches a length of 3 ½ inches and a weight of 30 grams (the weight of 2 sparrows). This is a burrowing species that forms permanent tunnels in sandy soil that may reach a depth of several feet. They emerge at night to feed on dried leaves that they frequently drag into their tunnels. As with hissing roaches, the young are born alive. They have a very long life cycle and require up to 7 years to reach adulthood.
Giant Rhinoceros Cockroach. Image Dr. Kaae.
In Australia they are frequently kept as pets and can be purchased in some pet stores where they are known as macrodogs. They have not reached the pet trade in the U.S. to any extent as it is illegal to export any insects (dead or alive) from Australia. Of course there are always some exceptions to the rule. In this case, if insects are captive bred they can be exported.
As with some of the larger insects, they are being bred in captivity in Japan and are sold for several hundred dollars each in that country. Insects as pets in Japan have become very popular. I am sure part of the reason is due to the lack of living space and insects take up very little space. In many cases, these insect pets sell for very high prices. I had a friend who was doing some work for National Geographic and ran across a new subspecies of a common rhinoceros beetle. He managed to collect 20 pair and brought them back to Japan and sold them to an insect breeder for $10,000 a pair.
Preventative Treatment. Typically cockroach infestations do not appear in the home or other structures on their own. On occasions, the American Oriental, smoky brown cockroaches and other predominately outdoor inhabiting species may move indoors on their own (normally a temporary situation). On the other hand, the German and brown-banded roaches are nearly always brought into homes by human activity. Actually, the German roach is very rarely found outdoors. There are some records of German roaches mass migrating from one structure to another but this is extremely rare. Once established, roaches have the potential to breed to huge numbers in a relatively short amount of time. As mentioned, one female German cockroach and her offspring have the potential of producing thousands of new roaches after 4 short generations. Obviously this potential is never reached or we would be literally swimming in cockroaches. A number of factors limit this potential include natural mortality, death during the molting process, available space, parasites, prevailing temperature, humidity and availability of food and water.
The presence or absence of these factors is of extreme importance in cockroach control. All structures have a limited capacity (carrying capacity) to support a cockroach infestation. Biological factors attempt to maintain insect population at that level, regardless of measures taken to reduce the population such as pesticide applications. As an example, when a number of cockroaches die as a result of an insecticide application, the reproductive rate of the remaining roaches will increase to replace those individuals and keep the infestation near or at the carrying capacity of the structure. As a result, an important phase of roach control is to attempt to reduce the carrying capacity of a structure. In some cases, the pest control operators will not be able to accomplish this on their own, but they can attempt to educate the client and thereby increase the chance of successful control.
The most important areas that can be controlled in order to reduce the carrying capacity of a structure are the availability of food, space and water. A tiny quantity of water (less than a drop) is all that is needed to sustain a roach for weeks or even months. Obvious sources of water include small leaks, condensation on pipes, moist sponges, moist food and even soaked wood. Roaches eat almost anything including paper, hair, crumbs, feces, fingernail clippings, spots of grease, pet fur, oiled clothes, bedbugs and dead insects (including dead cockroaches). They will cannibalize their own young and egg cases if food becomes scarce. Food high in protein or containing significant moisture is very attractive to roaches. However, if forced to feed on less nutritious food such as wood, soap, fingernails, their natural mortality rate will increase and their reproductive capacity will decrease.
Domestic roaches are positively thigmotactic, and they hide during the day where they have a surface touching the top and bottom of their bodies. This normally equates to crack and crevices that are around 1/16th inch wide. They also prefer to sit on soft surfaces such as paper and wood rather than metal. Their flat body allows them to squeeze into places where they can touch the surfaces above and below at the same time. Additionally the warmth around motors of refrigerators and dishwashers is attractive, especially if there is a drip pan under the refrigerator which provides water. Roaches commonly infest computers, television and microwaves all of which provide tights spaces and heat. In summary, one of the aims of a successful pest control program should include the reducing the availability of those factors (discussed above) that determine the carrying capacity of a structure.
Limiting the Availability of Water. Plumbing. Of the factors discussed above, availability of water is probably the most significant in reducing roach populations. As with humans, roaches can survive much longer without food than they can in the absence of water. Plumbing is one of the most common sources of water for these insects. Any leaking faucets including a loose gasket at the base should be replaced or repaired. Normally, if a faucet leaks at the base, this occurs when the water us running. Roaches will crawl up into faucets for water. If the screen that breaks the flow of the water into a steady stream is missing or damaged, it should be replaced. Plumbing beneath a sink should be examined for leaks and repaired. A whitish residue on these pipes indicates a slow leak. Pipe insulation may be required in order to prevent condensation from forming during humid conditions in the summer. Pipe insulation ideally should be sealed in order to prevent roaches from hiding between the insulation and the pipes. Generally kitchen sink strainers will not exclude roaches from entering drains for moisture.
Limiting Food Supply. Sanitation begins with a total clean-up of the cooking area. Areas under the refrigerator, stove and freezer can harbor large numbers of food. The outside of the appliances should be thoroughly cleaned. A tremendous quantity of nourishing food can accumulates under a stovetop. Accumulation of grease is of special importance as roaches consider it an ideal source of food. Roaches readily feed on the thin layer of grease on oven-hoods and walls next to or behind where grills, or frying pans are used. If possible, foods should be stored in cockroach proof containers. Considering the feeding habit of roaches, this can be difficult. Unfortunately, these beasts can chew their way through most types of packaging including aluminum foil, thin soft plastic, cardboard and paper. Food should be left out overnight, especially on dirty dishes in the sink. It is difficult to completely deprive roaches of a food source, but limiting food sources can help in the overall control of these pests.
Unlike humans, cockroaches make little distinction between a gourmet meal and garbage. Garbage disposals should be used on a daily basis and should be flushed thoroughly after each use. The top cover to the drain leading to the disposal should be in place when the disposal is not in use or at least during the night. All food preparation surfaces, pans, pots and dishes should be thoroughly cleaned after eating but certainly before retiring.
Eliminate Hiding Places. Roaches prefer to rest in small, tight places and on porous surfaces such as cloth, paper as opposed to aluminum, stainless steel, ceramic tile, plastic laminates, and baked enamel surfaces. These so called "soft" surfaces are layered (such as corrugated cardboard), an ideal site for cockroach resting and breeding is the result. Never keep paper sack, bags, rags, cardboard boxes or pieces of wood in locations where cockroaches may be present. One of the biggest mistakes is to store paper sacks next to the refrigerator because it provides a layering effect next to a warm area and high source of humidity. Equally troublesome is the storing of paper bags in layers in kitchen drawers.
Ideally narrow cracks, seams and crevices should be sealed in order to reduce the hiding places of roaches. Frequent hiding places include small holes, in seems beneath kitchen tables and cabinets, behind molding, around rubber gaskets on refrigerators and freezers, and where walls and cabinets meet, or around built-in appliances. Caulking is the most commonly used material to seal most of roach hiding locations. Silicone caulks are preferred as they do not crack or shrink, and cannot be chewed through by cockroaches.
Chemical Control. Chemical control is more difficult for the homeowner as opposed to the professional exterminator. The main advantage the professional has is the range of products available. However, there are effective products available to the homeowner. It is important to read the pesticide label before selecting a product and to precisely follow its directions when using any pesticide product. Most importantly, the product should be developed for roach control and should have some residual activity and remain active for days if not weeks. It is not important to apply the chemical directly to the roach but is more important to apply it to where the roaches hide during the day. Keep in mind that roaches are positively thigmotactic and hide in cracks and crevices. Generally speaking, roach motel type products and aerosol bomb are not that effective in this author's opinion. There a number of very effective cockroach baits.
Poisonous Baits. As their name implies, baits are formulate by mixing a pesticide with an attractive food which when consumed kills the pest species. They are useful for controlling pests such as flies, rats, mice, squirrels, cockroaches and ants. Often the whole area doesn’t need to be treated, just those spots where the pests gather. Usually only small amounts of pesticides are used in comparison to the total area treated. As a result, the potential for environmental pollution is minimized.
The main problem with controlling infestations of cockroaches is ensuring that enough insecticide gets to a sufficiently large proportion of the population to affect control. Cockroach infestations have been treated with insecticidal sprays, dusts, gels and baits. Cockroach bait may consist of simple poisons, killing from direct feeding only to the latest insecticides which use delayed transferred toxic action.
Secondary transmission of toxic baits. Cockroaches eat the feces of other roaches and they feed on each other. After consuming a lethal dose of a residual bait insecticide known to have delayed toxicant activity, cockroaches return to the harborage where they excrete feces. The insecticide-laden feces, fluids and eventual their carcasses can contain sufficient residual pesticide to kill others in the same nesting site. As the roach staggers around for hours or even days, it infects other roaches in the nest with toxicant transfer through feces. These can in turn infect others. The cascading effect goes on to wipe out whole colonies from indirect exposure by contact with the corpses, feces, or harborages of cockroaches previously exposed.
Active ingredients. Such roach baits may contain the active ingredient Fipronil .05% or Hydramethylnon 2%, available from Maxforce and Combat. The active ingredient Fipronil .05% disrupts the insect central nervous system leading to the cockroach’s death in 6 to 24 hours. Cockroaches nestling together transfer insecticide to one another by touch. Fipronil acts as an insecticide via contact, and as a stomach poison. It is somewhat soluble in water and is stable at normal temperatures for one year. Fipronil is an extremely active molecule and is a potent disruptor of the insect central nervous system. Fipronil bait is more effective and kills faster than Hydramethylnon. Mortality rates caused by secondary transmission are higher for Fipronil bait than for Hydramethylnon bait. Fipronil may be found in Maxforce®, Combat® and Siege®. Fipronil is a known carcinogen and has caused tumors in rats.
The active ingredient Hydramethylnon 2% when used as a cockroach bait leads to death in 2–4 days. Hydramethylnon inhibits mitochondrial energy production and has delayed action. After a single feeding, there are no immediate symptoms of poisoning, but within a few hours, the insects become lethargic and stop eating. This condition progresses until the insects die within 24 to 72 hours. Hydramethylnon kills insects by disrupting energy production in their cells. Hydramethylnon is a slow-acting stomach poison (delayed toxicity) that does not need to be eaten to be effective. It is toxic to cockroaches both by topical application and by ingestion. Hydramethylnon residues are much less active against cockroaches by contact than by ingestion. This slow-acting poison is desirable since roaches have long enough to return to the colony to share it with others. Hydramethylnon is used in Maxforce®, Combat®, Siege®, Amdro® and Sensible®. Hydramethylnon is known to cause cancer in rats, particularly uterine and adrenal tumors and lung cancer.
Boric acid is not dry bait but a dust that is both a toxin and a desiccant. Boric acid is often formulated into a paste. Roach attractants are mixed with the boric acid. It is similar in consistency to toothpaste. Boric acid roach baits consist of a proprietary blend of attractants. These products are often sold at exterminator or pest supply houses. They are sold at most hardware stores and some big box home improvement or retail stores. Boric acid is harmful to humans, children and pets.
Bait Placement. Cockroaches tend to live in groups with other cockroaches in the darkest shelters available. They instinctively choose darker over more illuminated areas. Cockroaches will settle in if a place is dimly lit and well-populated, and will use their antennae to feel whether other cockroaches are present.
The best way to determine the extent of cockroach activity, and hiding places is to look for them at night. Cockroaches are nocturnal and the few observed during the day are likely forced out by overcrowding; this is a possible sign of severe infestation.
For baiting to be effective, proper placement and techniques are a must. Put baits as close to their congregation sites as possible. A bait just 50 cm further away from such a location can reduce the amount consumed by half. If the same amount of bait is used to cover two areas, the area with the greater number of placements will also have the most consumed. One should avoid spraying insecticides in baited areas. That can cause the bait to become contaminated, thus the roaches would likely avoid consuming it. Baits, gels and Insect Growth Regulators can be useful in many cases. Bait placed in the open, away from a wall, is essentially non-effective because cockroaches are less likely to locate it. A small quantity of bait in many locations provides better control than large quantities in a few locations.