Aug 1, 2012 – To Repel or Not To Repel
QUESTION:
Which pesticide chemical families are considered repellent and which are considered non-repellent?
ANSWER:
Traditionally we think of the Synthetic Pyrethroids as the main group having some level of repellent effect on many insects. This has been known for a fairly long time and some manufacturers, initially, even lobbied for this repellency as a feature that could be exploited in managing certain bugs. For example, early on cyfluthrin (in Tempo) was known to be highly repellent to ants and it was suggested that the repellency could form a barrier around a structure that might keep ants away, thus protecting the structure. However, what was found was that it also could be a barrier to ants already within or under a structure, preventing them from leaving to the outside to forage for food, and in some cases it may have caused ants that otherwise were not a problem to begin foraging within that structure in their effort to find food.
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Which pesticide chemical families are considered repellent and which are considered non-repellent?
ANSWER:
Traditionally we think of the Synthetic Pyrethroids as the main group having some level of repellent effect on many insects. This has been known for a fairly long time and some manufacturers, initially, even lobbied for this repellency as a feature that could be exploited in managing certain bugs. For example, early on cyfluthrin (in Tempo) was known to be highly repellent to ants and it was suggested that the repellency could form a barrier around a structure that might keep ants away, thus protecting the structure. However, what was found was that it also could be a barrier to ants already within or under a structure, preventing them from leaving to the outside to forage for food, and in some cases it may have caused ants that otherwise were not a problem to begin foraging within that structure in their effort to find food.
Pyrethroid termiticides also have been shown to act as a repellent to the movement of foraging termites, and I recall at least one discussion of this at a major educational conference. One of our university researchers presented findings showing that foraging subterranean termites would quickly turn away from soils treated with pyrethroids. Again, this could be a benefit or a detriment. If the treatment of the soil was thorough and without any "breaks" those termites would continue to be repelled from the structure, but if there were breaks in the treatment the termites could eventually find them and move on through in their pattern of continuous wandering and searching.
Even WAAAYYYY back in the Olden Days when I started in this industry we relied on Organophosphates (diazinon, chlorpyrifos) and Chlorinated Hydrocarbons (lindane, chlordane) and loved the fact that those hydrocarbons might last for 30 years or more in the soil beneath a house. We could treat a landscape for ants with chlordane and not see any more ants the rest of the season. But, one respected industry leader suggested that the reason those ants stayed invisible was due to the long lasting repellency of the chlordane, so repellent the ants preferred to stay in their colony and starve rather than come out and walk on that chemical residue. We knew that OP's were repellent to ants and to roaches, and found that hiding the active ingredient within capsules ("microencapsulated" products like KnoxOut 2FM) would minimize that repellency and allow the ants to wander on our treated surfaces.
Now, of course, we have an ever-expanding arsenal of "non-repellent" active ingredients and the obvious benefits of them. Since our goal is to achieve contact time between the active ingredient and the pest bug we must provide a treated surface that they willingly stand on. We still should, whenever possible, make the application directly INTO the harborage point of the bug, rather than on nearby exposed surfaces where the bug may spend minimal time and the a.i. will more rapidly degrade.
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