Richard A. Dybas

Abamectin Use in Crop Protection

Initial indications that the avermectins possessed activity against arthropods were obtained in studies with avermectin B1a against the confused flour beetle (Tribolium confusum) and the sheep blowfly larva (Lucilia cuprina). Evaluation of the 8 major natural avermectins and several hundred semisynthetic avermectin analogs and derivatives showed that avermectin B1, the major component of the fermentation of Streptomyces avermitilis, was extremely toxic to acarines and to a wide range of insects, including members of the orders Diptera, Homoptera, Coleoptera, and Lepidoptera (Putter et al. 1981). Avermectin B1 (MK-936), with the common name abamectin, was selected for use against arthropod pests of economic importance in horticulture and agriculture.

AVERMECTINS: THEIR CHEMISTRY AND PESTICIDAL ACTIVITIES

ABSTRACT The avermectins, a novel class of compounds isolated from fermentation of the soil organism Streptomyces avermitilis , consist of eight major components with potent anthelmintic and insecticidal activities. These natural products are described as pentacyclic lactones containing an α-L-oleandrosyl-α-L-oleandrosyl dissacharide attached to the macrocylic lactone ring through the allylic C 13 -hydroxy group. The structure and stereochemistry of the avermectins were determined by spectroscopy, chemical degradation, and x-ray crystallography. A series of derivatives were prepared for biological evaluation through selective reactions of the natural products. A synthetic derivative 13-deoxy-22,23-dihydroavermectin B 1 b aglycon proved identical to the microbial metabolite milbemycin B41D. The avermectins have demonstrated high potencies in laboratory and field evaluations against agricultural and household insect pests in several Orders, phytophagous mites, and the plant parasitic nematode, Meloidogyne.