[Emerging Pests] Asian Cockroaches Invade Texas

The Asian cockroach, Blattella asahinai, has been discovered in Houston, Harris County, Texas. Collections from commercial buildings, residential areas and feral sites indicate that the Asian cockroach has been present in the Houston area for at least several years prior to its discovery this year.

First identified as a newly introduced species near Lakeland, Fla., in 1986, the Asian cockroach, a native of Japan, has spread to infest much of central and south Florida, portions of southern Georgia, southwestern Alabama and Charleston County, South Carolina. It is unknown if the Texas infestation is a range extension of the populations in Florida and other southeastern states, or if it represents an unrelated introduction.

Similar in appearance to the common indoor German cockroach, the habitat and behavior of the Asian cockroach differs markedly from its domestic cousin. Asian cockroaches are both feral and peridomestic. That is, they can live outdoors away from human habitation, but also are found in and around human dwellings. Asian cockroaches prefer outdoor areas that are shaded and covered with leaf litter or grass. German cockroaches, which are almost never found outdoors, prefer indoor cracks, crevices and clutter usually associated with moisture in places such as kitchens and bathrooms.

Perhaps the most troublesome difference for homeowners between German and Asian cockroaches is that while the German cockroach is unable to fly, the Asian cockroach is an excellent flyer. Asian cockroaches typically are most active during the first hour after sunset. Their frenzy of activity begins on the ground in the grass and plant duff, with roaches scurrying around and climbing to the tips of blades of grass and leaves of plants and weeds. The adults then take flight and are attracted to bright lights on porches, lights in windows and the lighted walls of commercial buildings. Some of the cockroaches will then find their way into homes and businesses.

The infestation we discovered in Houston was found during May 2006 and is located in the western portion of Harris County, about 18 miles west of Houston. Asian cockroaches were originally found flying to the lights surrounding a car dealership and then crawling into the showroom. Each morning dozens of adult Asian cockroaches were found covering the showroom floor. This activity has continued through the first week of August. The dealership sits on Interstate 10 and backs onto the Barker Reservoir. All life stages of the Asian cockroach were found in leaf litter under trees within 125 meters of the back of the dealership and approximately 315 meters from Interstate 10. Since the original discovery, Asian cockroaches also have been collected in residential areas to the east and west of the Barker Reservoir.

It is reported that the Asian cockroach can achieve population densities of 30,000 to 250,000 cockroaches per acre. This, and the fact that the Asian cockroach can fly up to 120 feet in a single flight, means the possibility exists that cockroaches can invade or re-infest from adjacent properties. While most insecticides are affective against the Asian cockroach, its outdoor habitat, ability to fly and high reproductive potential will make it a difficult pest to manage.

The author is president of Entomology Associates, Houston, Texas, and can be contacted at jtucker@giemedia.com.