Efficacy of Malathion Against Coleopteran Populations in Newly-Harvested Versus Year-Old Stored Corn2

Abstract

The impact of malathion treatment and duration of storage prior to treatment on species composition and relative abundance of beetle pests was investigated in shelled corn in newly-constructed galvanized steel bins. Corn was sampled monthly for insects with plastic probe traps from January through September 1989. Red and confused flour beetles, Tribolium spp., hairy fungus beetle, Typhaea stercorea (L.), flat and rusty grain and flour mill beetles, Cryptolestes spp., and foreign grain beetle, Ahasverus advena (Waltl), were most abundant in traps, but plaster beetle, Cartodere constricta (Gyllenhal), minute brown fungus beetle, Corticaria pubescens (Gyllenhal), antlike flower beetle, Anthicus spp., and larger black flour beetle, Cynaeus angustus (LeConte), also were trapped. Greater numbers of the four major beetle species were trapped in older corn and in corn that was not treated with malathion and, depending on species, trap catch peaked in August or September. Information gathered during this investigation adds to our knowledge of insect infestation and insecticide application to on-farm stored corn and confirmed earlier reports that T. stercorea and A. advena potentially are pests of stored shelled corn. Thorough inspection and sampling should be conducted throughout the storage period, but especially after grain temperatures warm above 20°C.