“Whatever you throw at them, they have an amazing ability to quickly adapt and overcome adversity,” said Phil Koehler, an entomology professor with UF’s Institute of Food and Agricultural Sciences. “We know that 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 the bait-avoidance problem was first noticed about five years ago in Florida, where the state’s warm climate is ideal for roaches, and in recent months has spread to other states as far north as Michigan.
“In Florida, pest control operators say that 60 percent of their customers have German cockroaches (Blattella germanica) that are refusing to eat most commercial baits, indicating there is something in the baits that roaches do not like,” he said.
Koehler and Barbara Bayer, a graduate research assistant, are working with pest control operators and product manufacturers to develop and test more effective baits for the German cockroach.
“It’s the roach that gives all other cockroaches a bad name,” Koehler said. “It’s also the most common cockroach species in homes, apartments, restaurants, hotels and other institutions in the United States and in most parts of the civilized world.”
As a result of their research, two new bait products designed for use by pest control operators have been shown to kill cockroaches that are refusing to eat existing baits, and the UF researchers are monitoring their effectiveness. The new products are Advion roach bait manufactured by Dupont and Max Force FC Select roach bait made by Bayer Environmental Sciences.
“It remains to be seen how long these two products will be effective,” said Bayer, who is not affiliated with the bait manufacturers. “Ten years ago, German cockroaches began avoiding baits that contained glucose sugar, and now they are developing an ability to avoid other ingredients in some of the newest baits on the market. We need to learn more about which chemicals they like and do not like.”
Koehler said that their research shows that the development of a more effective bait will also provide a secondary kill of the pest.
“Some of the cockroaches that avoid the bait in the first instance will eat dead or sick cockroaches that did consume the bait, resulting in a secondary kill,” he said. “But wait, the yuck factor gets worse – some of the roaches that avoid the bait will consume contaminated fecal matter or vomit from dead or sick roaches that ate the bait, which then will kill them.”
He said their rapid reproductive cycle allows them to quickly develop resistance to chemicals and avoid toxic ingredients. If just a small percentage of the roach population is able to avoid eating a toxic chemical, those cockroaches would be able to reproduce in exponential numbers.