Project Code: CE0310
Funded By Department for Environment, Food and Rural Affairs
Lead Research Centre
Central Science Laboratory,
Abstract of Research Proposal:
The main objective of the proposed work is to identify and evaluate the effectiveness of semiochemicals as multi-species lures to improve detection of the main insect pests and enhance other methods of protecting grain. It will achieve this by following a structured approach to identify and improve the characterisation of attractants and by investigating the various ways in which semiochemicals might be exploited in grain protection. The results of this work will provide a basis for industry development and take up and will contribute directly to the integrated management practice for UK stored grain. The work is relevant to policy on cereal production because it aims to maintain and raise grain quality by helping farmers and the trade to reduce insect presence while minimising the use of pesticides. It will achieve this by facilitating non-chemical methods and better targeting of conventional pest-control treatments, thereby improving the competitiveness of the UK cereal industry and addressing end user requirements.
Summary of Objectives
1) Identify and test the main active components of food attractants and insect pheromones, alone or in combination, to produce effective multi-species lures and enhance pest detection.
2) Assess semiochemicals having significant effects on feeding behaviour, mating or movement of grain storage insect as potential elements in integrated grain management.
Summary of progress from 98/99 annual report:
The purpose of this project is to develop lures which will attract, and thereby enhance the detection of, the most important species of stored grain pest. The work is focusing on the seven beetle pest species most frequently detected in UK grain stores, namely the saw-toothed grain beetle Oryzaephilus surinamensis, the grain weevil Sitophilus granarius, the rust red grain beetle Crytoplestes ferrugineus, the hairy fungus beetle Typhaea stercorea, the foreign grain beetle Ahasverus advena, the Australian spider beetle Ptinus tectus, and the white-marked spider beetle Pinus fur.
This project has started with a literature review of factors affecting the locomotory behaviour of these pests which could be exploited in the development of multi-species lures. Potential sources of new semiochemcials 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 mammal and birds’ nests. It might also be worth looking for new semiochemcials produced during the mass upward movement 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.
Behavioural influences which many conflict with the intended response to attractive lures include damaged grains, moisture and temperature gradients in the grain bulk which may be rival attractants, while many species prefer to avoid bright light. 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. Finally, opportunities to optimise the effectiveness of lures are highlighted, for example by improving the spatial distribution and physical attractiveness of traps and the incorporation of humectants in lures. The review is being issued initially as a laboratory report.
Interspecific interactions to stored product beetle pheromones have been reviewed to suggest sources of multi-species lures. Although insect pheromones are usually species specific, some grain pests are known to be attracted to pheromone components of other species. Beetle pests which exhibit cross-species attraction in pheromone components with other storage species are O. surinamensis, C. ferrugineus, S. granarius and A. advena. These interspecific attractions seem to affect only some, but not necessarily all, other species within the same family. These chemicals might usefully form part of a multi-species lure and will be worth further investigation. For this, it would be necessary to determine their relative effectiveness over a range of release rates and prove that they have no deleterious effect on the response of other families to their own pheromones.
Although no pheromone is known for T. stercorea, because it is associated with mouldy grain, it would be worth investigating fungal volatiles as semiochemicals for this species. The production of semiochemcials in spider beetles, including P. tectus and P. fur, has yet to be studied. This may become necessary if the pest status of ptinids continues to rise.
Electroantennography (EAG) is the measurement of the electrical energy elicited by responding sense cells across the whole antenna following stimulus with an odour. To determine whether EAG could help identify multi-species lures for stored product beetles, the EAG response of O. surinamesis was examined to seven macrolide lactone aggregation pheromones produced by five species of stored product beetle. Thresholds for perception of two of the lactones, both produced by O. surinamensis, were identified. The other lactones did not differ significantly from the control response at the quantities tested.
This test has shown that EAG can help rapid screening for volatiles of interest. Many replicates can be undertaken quickly. Valuable information can be obtained on perception thresholds and on the maximum concentration to saturate the receptors. EAG is highly appropriate for initial screening and identification of active volatiles from complex mixtures. Once candidate odours have been identified, the EAG technique provides a rapid means by which to determine the best candidate materials for use in behavioural bioassays. EAG does not indicate whether a behavioural response will be elicited by the materials giving an EAG response and if so whether this would result in attraction of the insect. However, by determining whether an insect can perceive a material and the concentration at which this occurs, considerable time can be saved when undertaking subsequent behavioural bioassays.
Volatiles which might form the basis of multi-species lures have been isolated from candidate food attractants by aeration. The foodstuffs aerated were carob, wheat, maize, oats, barley and peanuts, these being chosen because they were expected to be the most attractive to a range of insect pests of stored commodities. The foodstuffs were frozen beforehand to kill any mites and analysed for pesticides. Each aeration and extraction resulted in the production of 10ml of extract in pentane at a concentration of 23800 gh/ml.
Start date: 01/04/98
Completion date: 31/03/02