Chemical insecticides and repellents play a dominant role in protection of crops, livestock, homes, pets and humans from arthropod pests and disease vectors. Since the advent of widespread use of synthetic organic and microbially-derived insecticides in the 1940s, insecticide resistance and increasingly stringent regulations have fostered a continuing demand for new modes of action, which the chemical industry has been able to deliver at a steady pace. In the early 1980s, companies began hiring biologists to study these new modes of action, and I am fortunate to have been among them and to have had the opportunity to study successive generations of novel insecticides. I will briefly summarize this work, which includes studies on the mode of action of pyrethroids, fiproles and neonicotinoids on already known targets, as well as the identification of the novel insecticidal modes of action of sodium channel blockers (indoxacarb and metaflumizone), nicotinic receptor allosteric modulators (spinosyns) and chordotonal organ TRPV channel modulators (pymetrozine, pyrifluquinazon and afidopyropen).  Innovation in repellents has been comparatively less remarkable, with the market still dominated by DEET, the first widely used repellent, which was introduced more than seventy years ago. The mode of action of DEET is still not understood, but is widely thought to involve disruption of olfaction. In the second part of this talk, I will describe the discovery of a novel sensory modality that is used by ticks in host-finding, and its disruption by low concentrations of DEET, picaridin, and other repellents. This new insight into host-finding by ectoparasites the mode of action of repellents could facilitate future discovery of novel repellents.

Mode of action of insecticides and repellents

256th National Meeting (2018)

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