Laboratory evaluation of diatomaceous earths, when applied as dry dust and slurries to wooden surfaces, against stored-product insect and mite pests

Abstract

Abstract The efficacy of Silico-sec ® and Diasecticide ™ applied as dry dust and slurry applications to wooden surfaces was assessed in the laboratory against adult Sitophilus granarius , and Lepidoglyphus destructor and against larvae of Ephestia kuehniella . Wood was used as the test substrate as it was considered to present a realistic challenge to efficacy due to its 3-dimensional structure. Against the insects, doses of 10 g/m 2 Silico-sec ® and 20 g/m 2 Diasecticide ™ were evaluated. Against the mite 1 and 3 g/m 2 of the respective Silico-sec ® and Diasecticide ™ dry dusts and 20 g/m 2 of the slurries were assessed. The effects on the insects and mites were assessed one day, 4 weeks and 12 weeks after treatment of the wood. Mortalities were evaluated after exposure times of 24 h and 7 days for the mite and insects, respectively, at conditions of 15 °C and 80% r.h., chosen to represent typical UK conditions after harvest. Of the four treatments, the Silico-sec ® dry dust was the most effective against all the pest species, producing 80–95, 100 and 93–100% mean mortalities of S. granarius , E. kuehniella and L. destructor , respectively, over the 12-week experimental period. The Diasecticide ™ dry dust produced 99 and 68–93% mortalities of the respective species. The slurry treatments were less effective than the dry dusts with the Silico-sec ® slurry producing 29–46, 83–97 and ™ slurry being ineffective against S. granarius and L. destructor and producing 34–61% mortality of E. kuehniella . This study built on information gained from preliminary work and assessed DEs against tolerant pests on a surface where control was expected to be difficult, in order to provide dose recommendations which would encompass a range of infestation situations in the field.