Factors affecting the behaviour of beetle pests in stored grain, with particular reference to the development of lures

Abstract

This review summarises the published information on the behaviour of beetles in grain bulks that could lead to the identification of additional factors with the potential for enhancing existing lures or developing new ones. The review concentrates mainly on the adult stage of the five beetle pest species Oryzaephilus surinamensis (L.) , Sitophilus granarius (L.), Cryptolestes ferrugineus (Stephens), Typhaea stercorea (L.) and Ahasverus advena (Waltl) . After an analysis of the grain store environment and the origins of storage pests, particular attention is paid to behaviour associated with beetle movement and distribution within grain bulks, and their response to food and other multi-species attractants. Potential sources of new semiochemicals are identified; as well as the grains themselves, these include attractive volatiles associated with hot spots in grain, mouldy grain, and alternative insect pest habitats such as mammals’ and birds’ nests. It might also be worth looking for new semiochemicals produced during the mass upward movements of beetles from grain often seen following disturbance, although these could be repellents rather than attractants. Other sources of repellent semiochemicals with potential as grain protectants could be predatory and parasitic species of insects. Consideration is given to behavioural influences that may conflict with the intended response to attractive lures; for example, the presence of damaged grains, moisture and temperature gradients in the grain bulk may act as rival attractants, while many species prefer to hide away from bright light. As population densities rise, inter- and intra-specific competition becomes increasingly important. Human activities associated with grain handling, drying, cooling and pest control, as well as the presence of natural enemies and pathogens, all have the potential to affect insect response to a lure. Opportunities for the development of more effective lures are highlighted.