New insect control agents: modes of action and selectivity

Insect control agents remain an important part of most insect pest management (IPM) programs. Over the past decade, a variety of new insect and mite control agents have been developed, or are being developed, that may fit a variety of IPM needs, and many of these have novel modes of action. Several new acaricides acting at complex 1 of the mitochondrial transport system and chlorfenapyr, a proinsecticidal uncoupler, are representative of new compounds targeting insect respiration. Several diacylhydrazines (e.g. methoxyfenozide, an ecdysone agonist), along with pyriproxyfen, a juvenoid, are relatively new insect control agents that act on the insect endocrine system. Several new acaricides/insecticides (etoxazole, spirodiclofen) also disrupt mite and insect developmental processes. Among the new neurally active insect control agents, ethiprole (a phenylpyrazole) and emamectin benzoate both act on GABA gated chloride channel, although in very different ways, while indoxacarb acts at a novel site in the voltage gated sodium channel. Pymetrozine and IKI-220 act on the (aphid) insect nervous system in novel ways to disrupt feeding. There are several new neo-nicotinoids including thiacloprid, thiamethoxam and clothianidin that, like imidacloprid, are potent agonists for insect nicotinic acetylcholine receptors. The novel macrolide, spinosad, appears to alter the function of the nicotinic as well as GABA gated chloride channels in a novel manner. These recent new insect control agents demonstrate a variety of new and under-utilized modes of action. In many cases these new insect control agents also couple field efficacy with improved selectivity (compared to older chemistries) towards beneficial insects, especially predators. The preservation of a beneficial insect component in any IPM program is an important non-chemical source of selection pressure against a pest population, resulting, in not only in an overall enhancement in pest control, but a reduced likelihood of resistance development.