Pii: S0022-474x(99)00021-1

Source of diatomaceous earth (DE), insect species, grain moisture content, temperature, method of application and duration of exposure were all factors that in ̄uenced the mortality of stored-product insects. In all tests, regardless of the insect species, or source of DE, the lower the moisture content of grain, the greater the mortality. DEs from di€erent geographical locations had di€erent ecacies. The ranking of the di€erent DEs remained similar at di€erent moisture±temperature combinations. However, the mortality response with respect to moisture content did change among DEs from di€erent sources for Sitophilus oryzae (L.), but not for Tribolium castaneum (Herbst). Of all the insects tested, Cryptolestes ferrugineus (Stephens) was the most sensitive to DE. Oryzaephilus surinamensis (L.) and S. oryzae were more tolerant than C. ferrugineus. Rhyzopertha dominica (F.) and T. castaneum were the most tolerant species tested. Applying DE as a dust was more e€ective than applying DE as an aqueous spray. For C. ferrugineus, lower temperatures reduced DE ecacy. The opposite was true for T. castaneum, as lower temperatures increased ecacy for most DEs tested. For S. oryzae some DEs had increased ecacy with lower temperatures and others had decreased ecacy with lower temperatures. # 1999 Published by Elsevier Science Ltd. All rights reserved.