4.4 Avermectins

The avermectins are derived from a family of macrocyclic lactones produced by the soil microorganism Streptomyces avermitilis. Abamectin (avermectin B1) was introduced in 1985 as a crop insecticide against mites and some insect species. The semisynthetic derivative ivermectin (22,23-dihydroavermectin B1) was introduced commercially in 1981 as an anthelmintic. The recently introduced semisynthetic emamectin benzoate has unprecedented lepidoptera activity, controlling all lepidopterous pests on various crops at rates of 8-16 g/ha. While abamectin resistance is known in some species there is not yet convincing evidence for target site resistance, and there is no cross-resistance with emamectin benzoate²⁷.

Avermectins allosterically activate inhibitory glutamate receptors and potentiate the responses of those receptors to glutamate²⁸. With the introduction of emamectin benzoate, the inhibitory glutamate receptor is essentially a new target site for most lepidopterous pests.

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