Effect of Disturbance of Wheat on Four Species of Stored-Product Insects1

Abstract

Wheat infested separately with 4 species of stored-product insects was subjected to physical disturbance by being dropped in small sacks or through a tube from a height of 14.1 m or rotated and tumbled. These impact forces did not damage kernels or impair germination. Mortality of adults and larvae of the rusty grain beetle, Cryptolestes ferrugineus (Stephens), and the red flour beetle, Tribolium castaneum (Herbst), increased with increasing disturbance. Adults of the granary weevil, Sitophilus granaries (L.) and rice weevil, S. oryzae (L.). suffered 96% mortality when dropped in sacks. About 5% mortality occurred when granary weevils were dropped with free-falling wheat, and 13% when rotated and tumbled in sacks. Rusty grain beetles sustained a higher mortality than the other species in free-falling wheat or sacks subjected to rotation and tumbling. Reproduction by red flour beetles that survived impact in free-falling wheat was not impaired. Emergence of adult F1 progeny in disturbed wheat was reduced for the rusty grain beetle but not for the granary weevil.