Tim Lockley: Asian cockroaches are drawn to light

By Tim Lockley

When dinosaurs first showed up, cockroaches were waiting for them. They've been around so long that termites evolved from them. From the Carboniferous period 320 million years ago, these loathed arthropods have hardly changed. They haven't had to. They are nearly perfect for what they do.

I first found the Asian cockroach (Blatella asahinai) in Hancock County in an Africanized bee trap I'd set up. It was first discovered near Tampa, Fla., in 1986 and has managed, over the past decades, to expand its range throughout the Gulf States.

You may have noticed them and mistaken them for German cockroaches (the Germans call them the Russian cockroach). They do resemble each other quite closely but can be distinguished by their behavior. Both are 12 to 15 millimeters long, light to medium brown and have two distinctive parallel bars running down the length of the shield that covers the head. Both, as adults, have well-developed wings, but the German doesn't readily fly, while the Asian cockroach is a powerful flier and can travel up to 40 meters in a single flight. The German lives almost exclusively inside and only rarely ventures outside of a building. The Asian lives outside in mostly shaded areas with grass, leaf litter, mulch or other dense cover. German cockroaches are nocturnal (the Romans called roaches Lucifuga meaning "flees the light") and prefer to scuttle around in the dark. The Asian cockroach is attracted to light, which means you'll find them hanging around your porch light at night. If they get inside, they'll fly to your lamps and lit television screen.

Although most insecticides will kill Asian cockroaches, control is problematic because of their mobility and exceptional abundance (they can reach densities of over 600,000 per hectare). Perimeter treatments inside and out will have only limited effect, due to their widespread infestations. Even if you manage to control them in your yard, reinfestation will occur quickly as they move back in from your neighbor's yard. Controlling them requires a community effort. If you've got them, you can bet your neighbors have them as well. Talk to them (your neighbors, not the roaches) to set up some sort of coordinated effort.

When using residual sprays (such as bifinthrin, cyfluthrin or esfenvalerate), concentrate on the exterior -- around light fixtures, windows and doors. Spray your lawn, mulched areas, leaf piles and other shaded sites. If you're willing to do it, turn off exterior lights. If you can't, replace the bulbs with an old-fashioned yellow bulb for porch lighting and a sodium vapor lamp for your security light. Close the shades or blinds on your windows to reduce light leakage. If you find them in your house, you can remove them when they aggregate around lights by using a vacuum cleaner. Once collected, remove and dispose of the vacuum bag. Keep your lawn closely mowed and eliminate any clutter or litter around your home and out buildings. Exclusion techniques should be used on your house: caulking, screening and tight-fitting doors.

Although Asian cockroaches currently are susceptible to almost insecticide, baits are the most reliable. Baits containing hydramethylon or fipronil (Combat Plus, Combat Quick Kill Formula, Combat Source Kill) will quickly kill most Asian cockroaches. Another type of bait contains the insect growth regulators Abamectin B1 and Hydroplane (Raid Max).

Tim Lockley, a specialist in entomology, is retired from a 30-year career as a research scientist for the U.S. Department of Agriculture. For answers to individual questions, please send a stamped, self-addressed envelope to Tim Lockley, c/o Sun Herald, P.O. Box 4567, Biloxi MS 39535.