EFFECT OF INSECTICIDES ON THE PEA APHID, ACYRTHOSIPHON PISUM (HEMIPTERA: APHIDIDAE), AND ASSOCIATED FAUNA ON ALFALFA

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Abstract
Four insecticides effectively controlled the pea aphid, Acyrthosiphon pisum (Harris), but differed in their effects on other pest species and on predators. Two days after treatment, methidathion, dimethoate, and malathion reduced populations of all the pest species, but pirimicarb gave no control of the weevils Hypera postica (Gyllenhal) and Sitona scissifrons Say. Methidathion reduced populations of all predators, dimethoate reduced populations of all predators except Aeolothrips fasciatus (Linnaeus), and malathion reduced populations of all the predators except Nabis alternates Parshley. Pirimicarb reduced only the populations of syrphids. Of the insecticides tested, methidathion was the most disruptive to predators and pirimicarb the least.