EFFICACY OF THE DIATOMACEOUS-EARTH DRYACI DE(R) AGAINST STORED-PRODUCT PEST INSECTS

Efficacy of the diatomaceous earth Dryacide(R) against stored product pest insects The diatomaceous earth (DE) Dryacide(R) was tested under laboratory conditions on surfaces (2 g DE/m(2)) and in wheat grain (3 kg DE/t wheat) at a relative humidity of 70 +/- 5% and a temperature o f 22 +/- 1 degrees C. The wheat had a moisture content of 14.5%. The e ffect of surface treatments was tested on Ephestia kuehniella, Oryzaep hilus surinamensis, Tenebrio molitor and Tribolium castaneum. The effi cacy of grain treatments was determined using Ephestia elutella, O. su rinamensis, Sitophilus granarius and Tribolium confusum. In both treat ments adult and larval stages were included. 100% mortality were reach ed with the surface treatments in adults and larvae of O. surinamensis and the adults of T. molitor and E. kuehniella after an exposition ti me of 3-9 days. Against T. castaneum and the larvae of T. molitor and E. Kuehniella no complete control could be achieved. In the grain trea tments the dosage of 3 kg DE/t wheat reached 100% mortality in all tes ted pests except S. granarius. Most sensitive were O. surinamensis and E. elutella. In T. confusum the adults died within 13 days of treatme nt, but for complete control of the larvae 13 weeks were necessary. Ag ainst S. granarius the silica dust showed no satisfactory efficacy, be cause 49 days after beginning of the examinations beetles of the proge ny hatched. Dryacide(R) could not prevent the reproduction of the gran ary weevil, but there was a lower number of progeny compared to the un treated control.