I have had a hard time getting control of German cockroaches in a new account. I have tried bait, but they don’t seem to be eating it. Could the cockroaches be bait-averse?

If the bait is still intact when you do your return visit and you aren’t finding a lot of dead cockroaches where the infestation was the heaviest, it is possible you are dealing with bait-averse cockroaches. Bait aversion is a genetic trait that can be passed onto offspring that makes cockroaches averse to glucose, a popular bait component. German cockroaches will emerge from their harborages nightly to feed, so if your bait has been consumed you should be able to see results in a day or two. In heavier infestations, you may be able to bait near a harborage and draw cockroaches out to eat the bait immediately. If they don’t come out to eat and there are not a lot of competing food sources, the cockroaches are not attracted to the bait being used. Since this is a new account, try a few different kinds of bait to see if the cockroaches will accept a different brand or formulation.

How often should I re-apply a cockroach gel bait? 

How frequently you apply any cockroach gel bait can depend on a number of different factors. First, the application rate can change depending on the species you are trying to control. For example, you may have to bait more frequently for larger species such as American or Australian cockroaches because they can consume more bait per feeding than the same number of smaller German or brown-banded cockroaches. Another equally important factor to consider is the level of an infestation. A home heavily infested with German cockroaches would require more frequent baiting than a home infested with a much smaller number of American cockroaches. Temperature and humidity may also influence your need to reapply baits. If a gel bait is dried out, it will be less palatable to cockroaches. So, baits applied in warmer, drier conditions may desiccate faster and require more frequent reapplications. Lastly, your baiting schedule may be limited by the product itself. Therefore, you should always consult the product label to ensure all application and safety guidelines are followed.

I have been battling German cockroaches at one location and don’t seem to be making any progress with the gel bait that I typically use. I have even noticed that some cockroaches are ignoring the bait all together. Am I doing something wrong?

Many factors can impact the effectiveness of cockroach baits. One of the most common culprits is poor sanitation. Clutter and debris provide ideal harborage for cockroaches, while dirty dishes and food spills can offer food sources that compete with baits. Another important factor to consider is resistance. There are two major forms of resistance that can occur with cockroach baits: physiological resistance to the active ingredient, and behavioral resistance to inert ingredients such as glucose that are added to improved attractiveness to the bait. Glucose aversion has been documented in cockroach populations, and may explain your observation of cockroaches avoiding the gel bait. Rotating the baits you use every 90 to 120 days with different active ingredients and bait matrices can reduce potential resistance, and can improve the bait’s effectiveness. Lastly, how and where cockroach baits are placed can impact their performance. Apply the bait in small, pea-sized amounts, concentrating your applications in cracks and crevices where cockroaches are most likely to hide. Never apply new baits over old bait placements that have dried out and are no longer palatable. Be careful not contaminate baits by spraying over them with repellent insecticides or cleaning supplies. If you are a smoker, the nicotine in your cigarettes can get on your hands and contaminate baits. Always wash your hands and wear gloves before handling any bait if you smoke cigarettes.

How can I tell the difference between cockroach and drywood termite droppings?

To the untrained eye, drywood termite droppings, or frass, can closely resemble that of cockroaches. Both types of frass tend to be small, multi-sided pellets that are often compared to coffee grinds. However, there are key differences to look for that can help you to determine what pest you may be dealing with. Many cockroaches produce somewhat cylindrical fecal pellets that have a coarse surface, and are black to dark brown in color. The size of the pellets can vary depending on the size of the cockroach that produced them. Drywood termite pellets are more oval with a smooth, six-sided surface. They are uniformly sized and tend to be light brown, but can vary in color because they take on the color of the wood the termites are eating. The location and distribution of frass also can be useful in identification. Frass found in locations that lack wood, such as metal filing cabinets or drawers, are less likely to be from drywood termites. Also, drywood termite frass is ejected from galleries through “kick-out” holes, often accumulating into small piles beneath the galleries. Cockroach frass, on the other hand, is deposited infrequently and will not typically be found in piles.

How can I tell the difference between a German cockroach and an Asian cockroach?

The German cockroach (Blattella germanica) is one of the most ubiquitous pests on earth.  Originally thought to have originated in Europe, then Africa, the most recent theories surrounding its indigenous range trace it to Asia.  Today, it can be found on nearly every continent on earth (except Antarctica) and is almost always associated with human dwellings.

The species’ predilection for warm, humid environments make human structures, particularly areas where food is prepared, the perfect habitat for infestation.  Anywhere that humans are found, cockroaches are probably present too.  The Asian cockroach (Blattella asahinai), not to be confused with the Oriental cockroach (Blatta orientalis), has a more recent history of association with humans compared to German cockraoches.  To the casual observer, and even the seasoned pest management professional, the Asian cockroach looks nearly identical to the German cockroach.  They are closely related, but there are some key differences in behavior that make management methods different for the two species.

Asian cockroaches have longer and narrower wings compared to German cockroaches, along with a few other minor morphological differences.  The most obvious difference is the ability of Asian cockroaches to fly.  They are often attracted to lights and are most commonly found outdoors.  In North America, the Asian cockroach is currently known to be established in Florida, Georgia, South Carolina, North Carolina, Alabama, Louisiana and Texas, but has the potential to spread further throughout the United States because it can be established indoors.

I have a commercial customer with a large atrium inside the building.  I have collected multiple immature cockroaches that appear to be oriental cockroaches, but the adults I’ve seen have tan wings. The roaches seem to be living in the planters and mulched areas inside the atrium.  Any ideas what they are?

The insects in question are Surinam cockroaches (Pycnoscelus surinamensis), an exotic species that is established in the Gulf Coast states. In the northern parts of the United States, it is primarily a pest inside greenhouses and indoor atriums.  Adults are approximately 0.75 to 1.0 inch in length with wings that extend past the tip of the abdomen.  The cockroach is uniformly dark brown except for the front and side edges of the pronotum and wings which are light brown in color. The nymphs look a lot like oriental cockroaches, but upon closer inspection you will notice that the last five abdominal segments have a dull, rough appearance in contrast to the glossy sheen of the rest of the body.

Believe it or not, all of the Surinam cockroaches found in the continental United States are females.  It turns out that they reproduce parthenogenetically (without fertilization) resulting in the offspring being clones of the mother. No males have ever been observed for this species.  A closely related species, P. indicius is found in Hawaii and the Indo-Malayan region, and has both male and female forms.

Surinam cockroaches typically prefer to burrow into loose soil, leaf litter or mulch and remain hidden during daylight hours.  After dark, they emerge and feed on plant material, often causing substantial damage to plants in greenhouses and managed interior plantscapes.  Harborage areas are sometimes difficult to identify since these pests are known to burrow three to four inches deep and only emerge under cover of darkness or following heavy watering of potted plants.

When inspecting sticky traps, I noticed two projections off the back end of a brown cockroach.  What are these things and what purpose do they serve?

The projections you saw are called cerci, paired appendages and found on nearly every insect.  In some species, the cerci (singular: cercus) are large and pronounced; while in others they are reduced and hardly visible.  Given the discrepancy in appearance, you could rightly guess that they function differently for different insects.  In cockroaches, especially pestiferous species, cerci provide a valuable service in predator aversion.  Cockroaches love tight spaces, many of which allow cockroaches only to move forward or backward.  In this position, the cockroach can use its antennae and cerci to detect air movement and vibrations from ahead and behind.

The most prominent cerci in the insect world belong to earwigs.  Their cerci, commonly called pinchers, are used extensively in defensive behaviors, and will readily try to ‘bite’ you with them if handled.  The presence and activity of their cerci is most likely a major reason why earwigs are both detested and feared by homeowners.  For those identifying earwigs, this is a major feature used to separate species and even determine gender.  Some are toothed, some smooth, some cross over each other while others do not.