[Cockroach Control] Fighting Back

Preventing physiological resistance or behavioral aversion in insects is, at its simplest, a matter of using a variety of techniques and products for pest elimination. It is the industry’s dependency on and repeated use of a single active ingredient or formulation that most often causes insects to build a tolerance for or react aversely to a product or formulation.
So says Dr. Gary Bennett, professor, Purdue University, West Lafayette, Ind., who has spent more than 40 years studying the biology, ecology and management of structural pests. During the last few years, as bait aversion began showing up in cockroaches, Bennett and his colleagues in academia started conducting studies on the effects of baits on various cockroach populations. “All of a sudden we were starting to see a lot of situations, a lot of accounts where people could no longer get control using baits,” he says. The cockroaches wouldn’t eat the bait. “They may hang around, but they simply won’t eat (it).”
The difference in this situation and former resistance problems is that this is not a physiological resistance issue, but a behavioral aversion problem, which are two very different things, researchers are quick to point out. “In the past, we dealt with a resistance problem,” where insects adapted to the toxicant in a physiological way. But this issue, Bennett says, is not physiological in nature; rather the cockroaches have adapted their behavior so as to avoid the inert ingredients in the baits, one of the first instances of behavioral aversion in a pest (cockroaches) commonly encountered by pest management professionals. Further, Bennett says, “it’s when you have chronic, large populations,” that’s when resistance and aversion problems will “crop up.”
Dina Richman, product development manager, FMC Corporation, concurs with this assessment, noting that “aversion is really most (often) a problem in commercial kitchens; and we are hearing of it cropping up in low-income housing.” Although it is a low percentage of cockroaches that are currently averse, Richman sees the problem increasing. “I think it’s going to spread because we’re moving roaches from place to place.” In addition, she says, “We’re seeing an evolution in German cockroaches right now.” Physiological aversion is not new, but the ability of the cockroach to make behavioral modifications is new. In fact, she says, bait-averse cockroaches reared in the lab are different than normal cockroaches. “There is a physical component.”   
In many ways, the problem is a result of the advantages of baits — their efficacy, ease of use and applicability in sensitive areas. In the past, says Dave Naffziger, senior research scientist, Whitmire Micro-Gen Research Laboratories, the industry would hold meetings to discuss and plan cockroach strategies. “Then baits came along and we quit planning,” he says. In addition, many pest management professionals began treating only with baits. “It worked so well they didn’t do anything else,” Naffziger says, “but you need to do something else.” And that “something else” is exclusion, crack and crevice treatments, vacuuming and other IPM strategies.
The mentality of some technicians that if a little works good, a lot will work great also has led to aversion issues. At times when Whitmire Micro-Gen has stepped in to help PCOs, Naffziger says, “We literally had to go back to some accounts and scrape out the gel bait.” However, he doesn’t believe it’s a matter of lack of training; rather it’s a matter of applying the knowledge consistently in the field. “They all have the correct training, they just have to put it into practice.”
“There was a combination of pressures that led to the overuse of baits,” Bennett adds, one of which was the benefits of baits in sensitive areas. “Some government agencies were promoting or even requiring that only baits be used (in certain facilities). That put the industry under pressure.” Now that the aversion problem has developed, the government has become more amenable to other options.
Frank Meek, technical director, Orkin Pest Control, adds however, that technicians need to be careful not to blame aversion simply on improper treatment. “We have a tendency to blame every bait failure on it being bait aversion. We can’t do that.” Rather, he says, the technician needs to first verify that his or her work was done properly and that there aren’t other conditions contributing to the failure. When it truly is an aversion issue is when IPM practices need to be incorporated, with a return to conventional methods of dust, liquid residuals, insect growth regulators (IGRs), sanitation and exclusion, rather than a technician overusing the bait or switching to a different formulation or bait product because the population is not responding, Meek said.

MANUFACTURER RESPONSE. Most product development managers agree that it is the overuse of a single product or ingredient that has caused cockroach bait aversion. As a result, product manufacturers have been working during the last few years to formulate new cockroach baits, many of which have just come to market this year. 
Dr. Clay Scherer, development manager, DuPont Professional Products, says there is actually a 20-year history of bait aversion in cockroaches, but “in the last three or four years, there has been a growing need in the marketplace for a cockroach bait for what researchers are calling gel aversion or bait aversion.” In response to this, DuPont recently introduced Advion bait, which includes a unique formulation featuring indoxacarb, an entirely new class of insecticide and mode of action. “Insects have never been exposed to this mode of action so they are not predisposed to resistance,” he says.
Wellmark International launched its new Matrix gel bait at the 2004 PestWorld Convention, with production rolling out the first quarter of 2006, said Manager of Specialty Field Development Doug Vangundy. The bait was added to the company’s existing product line because Wellmark felt it would complement its IGR technology. The bait combines different food attractants, including proteins and sugar, with the active ingredient, hydramethylnon, in a bait formulation.
FMC’s Transport also came to market earlier this year. The bait, which incorporates the active ingredient acetamiprid, is “very active,” according to Richman. “We formulated a matrix that both normal and bait-averse cockroaches will eat.”
Whitmire Micro-Gen also introduced a new product in the fight against averse cockroaches. Avert, in a dry flowable powder formulation, has a dual mode of action and is now approved for food-handling areas. Not only are the cockroaches attracted to the bait as a food substance, Naffziger says, but it also adheres to their bodies so it is ingested during grooming.

BAIT ROTATION. In addition to applying various techniques for effective control, most of the product development managers recommended that technicians rotate baits to prevent aversion. “They really should be rotating product,” Richman says. “That way we can avoid physiological and, hopefully, behavioral aversion.”
Vangundy agrees. In addition to implementing an integrated pest management strategy to include monitoring, insect growth regulators and baiting, technicians should implement a rotational strategy between baits in order to prevent aversion.
Not only should technicians rotate baits, Naffziger adds, but they should rotate formulations, switching from gels to powders, and rotating between gels from different manufacturers.
The industry was there before with conventional cockroach treatments, Meek says, and he believes we will get to that point again. “We will have to go into some type of rotational pattern to try to stay ahead of this extremely intelligent insect.”
There are, however, dissenters to the rotation strategy. “Rotation is a strategy somewhat supported from agricultural resistance management,” says Dr. Byron Reid, product development manager, Bayer Environmental Science. He emphasizes “somewhat,” because there is just as much evidence that rotating pesticides simply increases the potential of resistance to both, he says. “It’s an easy thing for marketers to latch onto — saying you should rotate your baits — but quite honestly, it’s a fallacy,” Reid explains, adding, “The science doesn’t back it up.” Rotation has been tried before, he says. “It’s a simple concept for people to understand, but it’s never worked for aversion to cockroach baits.”
The strategy, instead, Reid says, should be to use a dose that is high enough to kill even the most tolerant ones.” That, he says, is exactly what Bayer did when formulating Maxforce FC Select, which has a concentration of fipronil much higher than even the most resistant cockroach can tolerate. “Maxforce was responsible for the original discovery of bait aversion in the ’80s,” Reid says, adding that, since then, Maxforce has been improved with advancing formulations, and Bayer continues to  conduct research enabling it to document that “its formulation is taking care of averse cockroaches and resistant cockroaches.”

THE FUTURE. Regardless of the specific bait a technician uses or whether or not he follows rotational strategies, it is imperative that the industry take a lesson from cockroach bait aversion and apply it across the board. Naffziger says too often the industry overuses a particular product technology or treatment technique when addressing pest problems. “Eventually, insects overcome many of our control efforts,” he says. “That’s why they’ve survived millions of years, but we shouldn’t help them by overusing a particular technology.”
Unfortunately, there will be such repercussions anytime the industry relies heavily on any one method, affirms Bennett. Thus, it is critical that PCOs not slip into the same routine with the newly introduced baits. “If technicians go out and depend entirely on those baits, you can bet the problem will crop up again,” he says. “Don’t depend just on baits. If you do that, it will catch up with you.”
But Bennett does see PCOs as being more aware of the issue, training accordingly, and implementing preventive measures. “The pest control industry is getting used to this,” he says. “They are doing things to provide better, more sustainable service.”

The author is a freelance writer based in Champlin, Minn., and can be reached at llupo@giemedia.com.