Texas Growers Could Benefit From Asian Cockroaches

For cotton farmers in south Texas, a predatory flying cockroach from Asia could turn out to be a highly beneficial insect, according to Agricultural Research Service (ARS) scientists in Weslaco, Texas.

Cockroaches are generally regarded as pests, but ARS entomologist Bob Pfannenstiel, at the ARS Beneficial Insects Research Unit at Weslaco, has seen a potential benefit from them as a natural control agent for insects that threaten U.S. agriculture.

Pfannenstiel studies predatory insects that feed on eggs of lepidopteran pests of annual crops. Lepidoptera is the insect order that includes moths and butterflies, including the cotton bollworm and the beet armyworm. He often spends his nights doing field tests on soybeans—a crop not often grown by farmers in Texas' Lower Rio Grande Valley. That makes soy a good crop for research purposes, enabling Pfannenstiel to make comparisons with cotton, the crop on which he does most of his work.

With technician Frank de la Fuente, Pfannenstiel starts putting out eggs of the cotton bollworm and beet armyworm at 3 p.m. in test fields. Then they measure predation at three-hour intervals for the next 24 hours. In the summer of 2006, they discovered a new predator in the system: the Asian cockroach, Blattella asahinai. Large numbers—up to 100 or more per square meter—showed up in soybean fields at Weslaco.

A strong flier first seen in Florida as a troublesome household pest in 1986, the nocturnal B. asahinai moved steadily westward, expanding its range at night and resting during the day on leaf litter or turf. Pfannenstiel’s results suggest that these roaches may become a dominant predator of pests in soybean and cotton in the Rio Grande Valley.

In addition to the curiosity of an invasive household pest serving a role as a biocontrol agent, the significance of this research is that it could influence the integrated pest management of important soybean pests. The frequency and timing of insecticide applications, for example, may be changed in order to allow the cockroaches to reduce the pest population naturally.

Read more about this research in the January 2008 issue of Agricultural Research magazine.

ARS is the U.S. Department of Agriculture’s chief scientific research agency.