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Spinosad
Aug 21, 2018

Spinosad is an insecticide based on chemical compounds found in the bacterial species Saccharopolyspora spinosa. The genus Saccharopolyspora was discovered in 1985 in isolates from crushed sugarcane which produce yellowish-pink aerial hyphae, with bead-like chains of spores enclosed in a characteristic hairy sheath. This genus is defined as aerobic, Gram-positive, nonacid-fast actinomycetes with fragmenting substrate mycelium. S. spinosa was isolated from soil collected inside a nonoperational sugar mill rum still in the Virgin Islands. Spinosad is a mixture of chemical compounds in the spinosyn family that has a generalized structure consisting of a unique tetracyclic ring system attached to an amino sugar (D-forosamine) and a neutral sugar (tri-Ο-methyl-L-rhamnose). Spinosad is relatively nonpolar and not easily dissolved in water.

Spinosad is a novel mode-of-action insecticide derived from a family of natural products obtained by fermentation of S. spinosa. Spinosyns occur in over 20 natural forms, and over 200 synthetic forms (spinosoids) have been produced in the lab. Spinosad contains a mix of two spinosoids, spinosyn A, the major component, and spinosyn D (the minor component), in a roughly 17:3 ratio.

Spinosad has been used around the world for the control of a variety of insect pests, including LepidopteraDipteraThysanopteraColeopteraOrthoptera, and Hymenoptera, and many others.It was first registered as a pesticide in the United States for use on crops in 1997. Its labeled use rate is set at 1 ppm (1 mg a.i./kg of grain) and its maximum residue limit (MRL) or tolerance is set at 1.5 ppm. Spinosad’s widespread commercial launch was deferred, awaiting final MRL or tolerance approvals in a few remaining grain-importing countries. It is considered a natural product, thus is approved for use in organic agriculture by numerous nations.Two other uses for spinosad are for pets and humans. Spinosad has recently been used in oral preparations (as Comfortis) to treat C. felis, the cat flea, in canines and felines; the optimal dose set for canines is reported to be 30 mg/kg.

Trade names include Comfortis and Trifexis (which also includes milbemycin oxime) (both brands treat adult fleas on pets; the latter also prevents heartworm disease), and Natroba (for human head lice). It is commonly used to kill thrips.