Behavioral responses of Sitophilus zeamais Motschulsky adults to conditioned grain kernels

Abstract

Laboratory experiments were conducted in order to assess the intra- and inter-specific interactions in cereal kernels and behavioral responses of maize weevil (Sitophilus zeamais) adults. For that purpose, conditioning of kernels was carried out in plastic boxes containing two caps; one with 2 g of maize, wheat or barley of different "kernel status": mechanically damaged, insect damaged or intact kernels, and the other with 2 g of whole maize kernels to be contaminated by the volatile semiochemicals released from the cap with the different "kernel status" grains. Depending on the test, kernel conditioning was carried out for various intervals, i.e., 1, 7 and 14 days. In the first experiment, three traps (three-choice tests) containing the semiochemically conditioned pairs maize-maize, maize-wheat or maize-barley kernels, with mechanically damaged, insect-damaged and intact kernels, were used. In the second experiment, two traps (two-choice tests) containing the conditioned pairs of maize-maize or maize-wheat or maize-barley kernels, with mechanically damaged, insect-damaged and intact kernels, were used. In the first experiment, when maize kernels were conditioned with maize kernels, significantly more S. zeamais adults were found in traps containing kernels conditioned by insect damaged kernels compared to traps with kernels conditioned by mechanically damaged or intact kernels at 1 and 14 days of conditioning intervals. When maize kernels were conditioned with wheat kernels, significantly more S. zeamais adults were found in traps containing kernels conditioned by insect damaged kernels compared to traps with kernels conditioned by mechanically damaged or intact kernels only at the 14-day conditioning interval. When maize kernels were conditioned with barley kernels, significantly more S. zeamais adults were found in traps containing kernels conditioned by insect damaged kernels compared to traps with kernels conditioned by mechanically damaged kernels again only at the 14-day conditioning interval. In the second experiment, when maize kernels were conditioned with maize kernels, significantly more S. zeamais adults were found in traps containing kernels conditioned by insect damaged kernels compared to traps with kernels conditioned by mechanically damaged kernels at all conditioning intervals, but results for maize kernels conditioned with wheat kernels were less clear. When maize kernels were conditioned with barley kernels, significantly more S. zeamais adults were found in traps containing kernels conditioned by mechanically damaged kernels compared to traps with kernels conditioned by insect damaged kernels at all conditioning intervals. (C) 2013 Elsevier Ltd. All rights reserved.