Asian roaches enjoying Florida vacation.

Asian roaches enjoying Florida vacation

Florida's infestation of flying Asian cockroaches has begun to resemble a bad dream scripted by Franz Kafka. The airborne intruder, Blattella asahinai, has spread to as many as 18 Florida counties since its U.S. introduction in 1984. And while federal researchers say they're on to some promising repellents, new insights into the roach's genetics suggest control will be difficult at best.

In parts of Florida, roaches are no longer a mere household hassle. B. asahinai has become a major pest in gardens and commercial spaces such as shopping malls, says Richard J. Brenner, a research entomologist with the U.S. Department of Agriculture in Gainesville, Fla. Transplanted to a climate resembling their native Okinawa, "these roaches are in hog heaven," he says.

Unlike the familiar German cockroach, which keeps all six feet on the ground and has a well-known predilection for lurking in the shadows, B. asahinai is attracted to light and enjoys a reasonable measure of aeronautical ability (SN: 7/11/87, p.23). "They are extremely strong fliers," sometimes staying aloft for hundreds of meters, Brenner said last week at the annual meeting of the Entomological Society of America in San Antonio, Tex.

Moreover, since the Asian roaches live in leaf litter and in the shade of sprawling citrus groves, they maintain a relatively impregnable outdoor base from which to launch their nightly invasions of well-lit buildings. Researchers estimate the insects have reached population densities exceeding 100,000 per acre in parts of the state.

Pest control businesses find the cockroaches a major economic liability because nearly a third of the residents in treated buildings call back within days to report new infestations, Brenner says. Houses built near orchards -- once coveted for their pastoral views -- are especially hard hit. "And if you're really unfortunate, you have a street light outside," he adds. "That really brings them into your neighborhood."

On commercial sites, where liability concerns require that buildings remain well-lit at night, customers commonly spot the critters along shopping aisles, inside vending machines and even in such "nontraditional sites" as bridal shops, says Brenner. And although the insects so far have not exacted substantial agricultural tolls in the state, backyard farmers report increasing damage to such varied crops as grapes, corn, tomatoes and strawberries.

Though the species is far more insecticide-sensitive than the German cockroach -- which has developed strong resistance to most insect poisons -- its maintenance of large outdoor populations makes traditional pest control strategies impractical. "You can't spray every square inch of Florida," Brenner says.

Moreover, adds Richard S. Patterson of the USDA's Agricultural Research Service laboratory in Gainesville, recent experiments indicate that hybrids of Asian and German cockroaches retain both the Asian ability to fly and the German resistance to insecticides. These crosses were performed in the laboratory, and entomologists have yet to see such hybridization in nature. However, says Patterson, "we haven't been actually searching [for hybrids], either."

Brenner says he and his colleagues have developed several novel roach repellents that show promise against German cockroaches and that should help deter Asian roaches as well. Rather than relying on biological poisons, the new repellents contain substances that physically irritate the roaches. "German cockroaches would rather stand under bright lights without food and water and starve to death than go into these [treated] areas," Brenner says. Details on the repellents remain proprietary for now.

Until such products hit the market and prove useful, the Asian cockroach problem is bound to get worse, Brenner concludes. Last year, 35 million people visited Florida, he notes. Seventeen million arrived by car and drove back to their home states. So, while scientists have yet to sight the pest beyond Florida's borders, "it would be foolish to think it's not elsewhere," he says.