Action of amorphous diatomaceous earth against different stages of the stored product pests Tribolium confusum, Tenebrio molitor, Sitophilus granarius and Plodia interpunctella

Environmental and human health problems associated with the use of syntheti c pesticides have prompted the demand for non-polluting, biologically speci fic insecticides. The current study tested the use and action of diatomaceo us earth against several stored product pests. Fossil Shield(R) applied to wooden plates was lethal to adult Tenebrio molitor and Tribolium confusum, but larvae of the mealworm were unaffected. Beetles died within 14 days exp osure in the absence of food to a dose of 2 and 4 g/m(2) but mortality was reduced in those fed grain bran. Fossil Shield(R) was lethal to first insta r larvae of Plodia interpunctella, but not lethal to older larval stages. T wo-week old larvae of T. confusum were more sensitive to diatomaceous earth than P. interpunctella at the same age. Contact with diatomaceous earth ca used adult Sitophilus granarius, T. molitor and T. confusum to lose weight and reduced their water content, suggesting disruption of "the water barrie r". Death of stored product insects treated with diatomaceous earth decreas ed with increased r.h., due to reduced transpiration through the cuticle. H igh r.h. delays, or above 60% can prevent, the drying action of diatomaceou s earth. (C) 2000 Elsevier Science Ltd. All rights reserved.