Efficiency and persistence of insecticides with different action mechanisms applied on wheat stored pest sitophilus zeamais

Abstract

Sitophilus zeamais is the most important insect-plague among stored grain pests. The method of chemical control based on phosphine is the most used for its control, however, this method presents some inconveniences, being a costly method in labor and dangerous to the operators from the toxicological point of view. Thus, the use of preventive control, which consists of the application of liquid insecticides on the mass of grains, during the loading of the warehouse, appears as an alternative against the attack of the pests that tend to settle in the mass of grains. Thus, the objective of this work was to evaluate the efficiency and persistence of insecticides with different mechanisms of action on S. zeamais on stored wheat, simulating ideal storage conditions. An experiment was performed composed of the active ingredients: abamectin, spinosad, lambda-cyhalothrin + chlorantraniliprole, bifenthrin as a positive control, and the negative control was distilled water. The experimental design was a completely randomized block design with four replicates. The wheat was stored in Gerbox containing 250 grams, all samples being treated directly in these containers by spraying the liquid on the wheat grains. After spraying, the samples were homogenized and infested with 15 adult individuals of S. zeamais and deposited in an air conditioned room at 30 ± 1 °C and relative humidity of 30 ± 2%, in order to provide conditions of high biological activity of the insects. The active ingredients spinosad and abamectin promoted a 100% control of S. zeamais up to 120 days of conduction of this assay. Regarding biological persistence, the active ingredients lambda-cyhalothrin + chlorantraniliprole and bifenthrin had control effects up to 60 days after application while the active principles abamectin and spinosad persisted until the end of the bioassay observations