Evaluation of stirring to suppress weevils in stored maize

Abstract

The maize weevil (Sitophilus zeamais Motschulsky) is found throughout the world and is among the most destructive pests of stored grain and grain products. Maize weevil suppression is difficult and chemical insecticides are frequently employed. Stored grain insects can also be suppressed by physical disturbance which involves movement of individual kernels with respect to one another. Stirring grain in a silo disturbs individual kernels but we don't know of any study on the effects of stirring on maize weevils. The objective of this research was to determine the effects periodic stirring weevil-infested maize has on maize weevil population density and on maize quality. Six 0.12-m3 (4.2-ft3) steel experimental containers were used in this study. Three of the containers were equipped with Sukup Fastir®™ stirring machines. All containers were loaded with 30 kg of maize and unsexed adult weevils were placed in each container at a density of 25 live weevils per kg of maize. Stirring machines were programmed to travel one length of the stirred containers every 12 h. At 40 days and at 80 days, no live weevils were found in samples from the stirred containers, but at 80 days, reached 18 weevils per kg in control containers. Stirring increased BCFM in the stirred maize by seven percentage points and decreased maize moisture by 0.2 percentage points compared to control containers. Mechanical damage and bulk density changes were inconsequential. Stirring shows promise as an effective non-chemical method for suppression of maize weevils, but studies at silo scale are needed.