Phosphine resistance in rusty grain beetles, Crytopolestes ferrugineus (Stephens), (Coleoptera: Laemophloeidae) from stored wheat in Oklahoma
Abstract: Phosphine gas, or hydrogen phosphide (PH3), is the most common insecticide applied to durable stored products worldwide and is routinely used in the U.S. for treatment of bulk-stored cereal grains and other durable stored products. Research from the late 1980s revealed low frequencies of resistance to various residual grain protectant insecticides and to phosphine in grain insect species collected in Oklahoma. Recent research conducted using populations of stored-product insects collected from Oklahoma commercial grain storage facilities showed that one Tribolium castaneum (Herbst) (Coleoptera: Tenebrionidae) population was 119-fold moreresistant than the susceptible strain and a population of Rhyzopertha dominica (F.) (Coleoptera: Bostrichidae) that was over 1,500-fold more resistant. The present work, which employed the same previously established protocols for phosphine toxicity as in earlier studies, evaluated adults of 13 populations of Cryptolestes ferrugineus (Stephens) (Coleoptera: Laemophloeidae), collected from four counties in the state of Oklahoma. All the 13 populations were resistant to phosphine. Two of the populations showed extremely high resistance frequencies of up to 100%. Future research will focus on conducting a wider survey of phosphine resistance in C. ferrugineus from Oklahoma and to perform dose-response tests to determine levels of resistance in field-collected populations with high resistance frequencies.