The IGR and Auto-Dissemination Process

 

Any eggs laid in this area by mosquitoes will be affected by the insect growth regulator and not develop into adults, thus terminating their life cycle. In auto-dissemination, any female mosquitoes that fly into and land in this area for egg-laying or resting will touch and contaminate their legs with the IGR. Later, when the mosquito lays eggs or rests elsewhere, that secondary area will also be contaminated with the IGR. Any eggs laid in this area will also be affected by the IGR and will not develop into adult mosquitoes.

 

The active ingredient in the IGR, pyriproxyfen, is moved by the mosquito effectively from one area to another, potentially affecting a new area that the PMP did not treat. “You’re letting the mosquito do the work for you,” said Tommy Powell, technical field specialist for MGK. 

 

What helps with the effectiveness of the process is that pyriproxyfen “can work with really, really small amounts,” even just a few molecules, explains Salem. 

 

“Insect growth regulators (IGRs) are insecticides that mimic hormones in young insects. They disrupt how insects grow and reproduce. IGRs can control many types of insects including fleas, cockroaches, and mosquitos. Although they are rarely fatal for adult insects, they can prevent reproduction, egg-hatch, and molting from one stage to the next. Many IGR products are mixed with other insecticides that kill adult insects.” — Source: National Pesticide Information Center (http://npic.orst.edu/ingred/ptype/igr.html)

 

To zero in on a neighborhood mosquito problem, PCOs need to “localize the points where mosquitoes are breeding, and attack those areas with larvicides and IGRs; that’s the way it has to be done,” says Salem. Using an IGR, pyriproxyfen, is “an extremely effective mosquito control” tactic, especially when utilized in an area where water is unnaturally found, like a cemetery vase, says Craig A. Stoops, Ph.D., B.C.E., and chief science officer of Mosquito Authority in Jacksonville, Fla. The IGR stops the mosquito from moving through its life cycle, he says.

 

John Bell, B.C.E., regional technical manager/staff entomologist for TruGreen in Orlando, Fla., describes one challenge and caution in using IGRs, however. Since mosquito larvae are found in water, if a PMP uses an IGR that is mixed with a pyrethroid to kill larvae and adults, “you can’t apply a pyrethroid in the water.” The challenge is to stay within the label restrictions and not contaminate the water with pyrethroid products, says Bell.

 

We carried out four field experiments in two areas of Rome, Italy, that are typically highly infested with Ae. albopictus. In each area we used 10 pyriproxyfen “dissemination” stations, 10 “sentinel” sites and 10 covered, control sites. The sentinel and control sites each contained 25 Ae. albopictus larvae. When a 5% pyriproxyfen powder was used to contaminate the dissemination sites, we observed significantly higher mortality at the pupal stage in the sentinel sites (50-70%) than in the controls (<2%), showing that pyriproxyfen was transferred by mosquitoes into sentinel sites and that it had a lethal effect. The results support the potential feasibility of the auto-dissemination approach to control Ae. albopictus in urban areas. — Source: Paraphrased from a study regarding the auto-dissemination approach to fight Aedes albopictus in urban areas from the U.S. National Library of Medicine National Institutes of Health (https://www.ncbi.nlm.nih.gov/pubmed/22953015)

 

Auto-dissemination is “something so amazing,” Salem said. The process might seem unreal because mosquitoes carry miniscule amounts of pyriproxyfen on their legs to contaminate other areas, but the product is designed to work effectively in very small amounts, says Salem. “We have research and proof that it happens,” he says. Salem explains that theses small amounts of pyriproxyfen work most effectively with Aedes mosquitoes because they are known to look for “small pots of water” rather than rivers or larger areas.

 

Not everyone in the pest control world is completely convinced of the effectiveness yet, but they are very hopeful. Stoops says he believes in the research and the researchers, but is anticipating seeing more field data. “It’s coming. We’ll have real-world examples,” he says. 

 

Similarly, Bell states, “I have to be cautious as a PCO with what works in a lab to make sure it works realistically in the field.” Bell, confirms, however, that his company is testing auto-dissemination now. “The case is there enough that we’re testing it. We’re not dismissing it,” he says.