Evaluation on the efficacy of spinosad dust against major storage insect pests

Abstract

Laboratory bioassay trials were conducted at the National Agricultural Research Laboratories and Kiboko sub-centre in Kenya to determine the efficacy of spinosad dust 0.125% admixed with shelled grains, compared to a “cocktail” of pirimiphos-methyl 1.6% and permethrin 0.3% (Actellic super dust) against four important storage-insect pests: Sitophilus zeamais (Motsch), Tribolium castaneum (Herbst), Rhyzopertha dominica (F.) and the larger grain borer, Prostephanus truncatus (Horn). Spinosad dust was applied at 0.35, 0.7 and 1.44 parts per million (ppm), and Actellic super dust at 10.5 ppm. All treatments were significantly (P=0.05) better than the control except when applied against T. castaneum. Spinosad at 0.7 and 1.44 ppm was able to controlS. zeamais over the 24-week trial period. Similarly, all treatments gave good control over P. truncatus and R. dominica, with not apparent significant differences (P=0.05) between treatments on the latter. On P. truncatus, Spinosad showed better performance than Actellic super dust (P= 0.05). All levels of spinosad dust appeared to perform better on P. truncatuscompared to Actellic super dust, but spinosad dust, unlike Actellic super dust, was unable to control T. castaneum. The evidence from this trial suggests that spinosad dust may have potential in controlling major storage-insect pests, with special applicability against the destructive larger grain borer, P. truncatus. Key words: Spinosad, Actellic, dust formulations, storage pests, pest control.