Fighting roaches a losing battle

University of Florida scientists suggest mankind can never win the war against German cockroaches, as the hated household pests become resistant to new poisons almost as quickly as the products are produced.

“Whatever you throw at them, they have an amazing ability to quickly adapt and overcome adversity,” said Phil Koehler, entomology professor at the university’s Institute of Food and Agricultural Sciences.

“We know they have developed resistance to many of the most widely used insecticides, and now they are turning up their noses at baits, including some that were very effective just a few years ago,” he said.

Mr. Koehler and graduate student Barbara Bayer are monitoring two new roach baits on the market, developed as a result of their research for use by pest control operators. The baits have been shown to be more effective in killing cockroaches than other baits now available, ones that roaches tend to avoid.

“But it remains to be seen how long these two new products will be effective,” Mrs. Bayer said yesterday.

She pointed out that in the 1990s, roach baits contained glucose.

“But roaches weren’t eating those baits, so manufacturers changed the ingredients and replaced glucose with another sweetener to entice them. That worked fine until recently.”

Mrs. Bayer called it “pretty inevitable” that roaches also will stop eating the new baits, Advion by Dupont and Max Force FC Select by Bayer Environmental Sciences. Mrs. Bayer is not affiliated with the bait manufacturers.

But it remains to be seen “how long it will take” for resistance to the new baits to set in, she said.

“Roaches are one of the most resilient — if not the most resilient — insect on earth,” said Cathy Mannex, spokeswoman for the National Pest Management Association.

“Every time you put a single food source out there [to kill them], they become fussy over time, so you have to rotate products.”

Dupont spokesman Mike McDermott said roach bait manufacturers are always trying to design toxic food products that “are more attractive [to roaches] than other foods.”

“Over time, roaches feeding on the same food look for something else,” Mr. McDermott said. “It would be like people eating pizza three times a day. It would be great for a while, but you’d eventually get tired of it.” He declined to disclose what Advion contains.

Mr. Koehler said the “toughness” of German cockroaches — the most common variety in this country — is evidenced by the fact that they have been around for about 3 million years, 10 times longer than humans.

“And roaches will be around long after we’re gone,” Mrs. Mannex predicted.

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