Roaches: The Battle Continues; Evicting the Most Common Roaches May Get Easier
Ralof, Janet, Science News
Roaches: The Battle Continues
Few fixtures of urban apartment life elicit such near-universal disgust as the cockroach. The tawny, half-inch-long German cockroach is the major indoor roach in North America, "probably in the world," according to Philip Koehler, a research entomologist with the University of Florida in Gainesville. But new technology has the potential to put these pests on the defensive. An arsenal of new weapons -- including several still under development -- should improve the success of tactical strikes against this age-old scourge.
The immediate benefit, besides peace of mind, should be better hygiene. Notoriously filthy, cockroaches have been known to carry the Salmonella bacteria that cause food poisoning, and have been implicated in spreading diseases like hepatitis. Improved roach control might also bring unexpected relief to many allergy and asthma sufferers.
At its Insects Affecting Man and Animals Laboratory in Gainesville, Fla., the Agricultural Research Service (ARS) has a team of cockroach specialists investigating everything from the insect's nutrition to potential birth control drugs -- all in hopes of learning how better to control the proliferation of this consummate urban survivor. The conventional wisdom is that if a female and all her progeny are given enough food and allowed to proliferate, a single fertilized roach can set up a colony of "close to a million offspring within a year," explains Koehler, who conducts much of his research at the ARS lab.
Most humans discourage such proliferation by baiting, trapping, spraying and just plain squashing the fleet-footed pests. Even so, roach populations can become disturbingly large in crowded, low-income areas, according to a two-year survey of German-cockroach populations just completed by Koehler and Richard Patterson, who studies household insects at the ARS lab. Involving more than 1,000 low-income apartments in the southeastern United States, the study found that 97.5 percent were infested -- with a minimum of 160 roaches per dwelling, and an average of 33,600. And those estimates are "conservative," Koehler believes.
The survey also tends to dispel the rubric that roaches prefer to dwell under the kitchen sink. Instead, it found that the best places to trap roaches are, in order, next to the garbage, on kitchen counters, and under the kitchen or dining room table. The insects' use of countertops as a major thoroughfare and for foraging "means that cockroach droppings, roach parts and probably cockroaches themselves are regularly being incorporated into meals," Koehler says. But the pests are not above making a meal of the humans themselves. Where infestations are heavy -- the worst cases may involve a quarter million -- the roaches will move into bedrooms. "In those cases," Koehler says, "the roaches will climb on people, gnawing off their eyelashes, eyebrows and calluses on their hands and feet."
These bugs can also prove a potent health hazard to those with allergies. Frank Twarog, an allergist at the Harvard Medical School in Boston, says his data suggest that 50 percent of people in the Boston area who have allergies and are exposed to cockroaches will develop an allergic sensitivity to the insects. In a study reported earlier this year, pediatric allergist Elsie Morris at Emory University in Atlanta found that of 48 inner-city children with chronic wheezing, runny eyes and runny nose, 37 proved to be allergic -- and more than half of those who proved allergic were sensitive to cockroaches. In fact, 20 of the 21 who tested positive for cockroach sensitivity were asthmatic. "That's serious," she points out. "Any asthma can be life-threatening." In fact, data by allergy immunologist Bann Kang at Mt. Sinai Hospital Medical Center in Chicago suggest that up to 50 percent of asthmatics with multiple allergies may develop cockroach sensitivities. Her data also show that cockroach allergens tend to elicit far more potent reactions than other substances to which an asthmatic is sensitive. …