Abstract

Laboratory experiments were carried out in order to evaluate the insecticidal effect of diatomaceous earth against adults of Callosobruchus maculatus (F) and Sitophilus granarius (L.), two important stored grain pests in darkness (30°C and 65% relative humidity). Wheat and cowpea were treated with the diatomaceous earth formulation Silicosec^® (Biofa, Germany), at five concentrations determined with preliminary tests and compared with untreated wheat and cowpea as control. Dead adults were counted 24, 36 and 48 h later. Results showed that increasing concentration of Silicosec^® and days after treatment (DAT) significantly increased the mortality rates of adults to above 90% in both experiments. Regarding LC₅₀ and LC₉₅ values, it was observed that C. maculatus adults are more susceptible to Silicosec^® than S. granarius. The results showed that these two pests could be controlled successfully with diatomaceous earth.

Key words: Callosobruchus maculatus, diatomaceous earth, Silicosec^®, Sitophilus granarius, stored grains, cowpea, wheat, effective concentration.