Survival and Reproduction of Stored-Product Mites and Beetles on Fungal and Bacterial Diets1

Abstract

The grocer's itch mite, Glycyphagus domesticus (De Geer), and the grain mite, Acarus siro L., which normally feed on grain dust, other stored foods and fungi, were exposed at 17±1°C and 75±2% relative humidity (RH) to 19 species (17 genera) of fungi and 6 species (5 genera) of bacteria. The rusty grain beetle, Cryptolestes ferrugineus (Stephens), which normally feeds on grain, and the foreign grain beetle, Ahasverus advena (Waltl) which is fungivorous, were exposed to bacteria only. Both mites thrived on Syncephalastrum racemosum, Absidia spinosa, and Curvularia geniculata, but failed to survive and multiply on Aspergillus ochraceus, Gliocladium roseum or Penicillium sp. G. domesticus multiplied 30 times on S. racemosum, and A. siro multiplied 40 times on A. spinosa. Neither of the 2 mites fed adequately or multiplied on any bacterial species. All mites died in about 35 days and 50% died in 5 days. G. domesticus died sooner (8 days) on Bacillus subtilis than on any other bacteria or fungi; A. siro died soonest on B. megaterium. Both species of insects (except C. ferrugineus on Agrobacterium radiobacter) died in about 21 days and 50% died in 7 days when exposed to pure extracts of bacteria. We conclude that bacteria, unlike fungi, adversely affect both mite and insect pests of stored products.