Improved detection and monitoring of beetle pests in stored grain through use of a multi-species lure (LK0929)

Abstract

All grain harvested in the UK will at some stage be stored, whether on farms, in central stores or at mills. In all these premises grain is at risk to infestation by a range of insect pests.  Effective detection of pest presence is essential in protecting harvested crops by revealing whether control is necessary and whether it has been successful.  Compliance with the Assured Combinable Crops Scheme requires that steps be taken to monitor for the presence of beetle pests, yet many feel that they cannot rely on the results as monitoring methods have not been optimised.

A previous Defra-funded project identified a mixture of materials which showed promise as a multi-species lure for the saw-toothed grain beetle, the grain weevil and the rust-red grain beetle in laboratory conditions.  The purpose of this project was to develop the first multi-species attractant lure for invertebrate pests of the cereals food chain by establishing a simplified mixture of easy-to-obtain compounds and proving activity against a wide range of beetle pests of the grain and milling trades.

Effects on insects of a mixture of volatiles obtained from peanuts and kibbled carob were evaluated. All individuals of a particular species detected less than 10% of the 180 compounds present and different species responded to different compounds. Behavioural bioassays of these compounds, together with other compounds identified from the literature as potential attractants, found that five of the 14 compounds tested against the grain weevil, seven of the ten compounds tested against the saw-toothed grain beetle and five of the ten compounds tested against the rust-red grain beetle were attractive.

From these a total of 11 compounds were chosen for further investigation, of which only two were attractive to all three species and five were attractive to at least two species. A six-component mixture consisting of hexanoic acid, 3-methylbutanol, 4-ethylacetophenone, 3-octen-2-one, nonanal and E-2-nonenal was attractive in laboratory bioassays. In addition, this six-component mixture was attractive to an additional four species of stored product pest. This mixture was formulated into a range of dispensers and a polyethylene vial was the most effective dispenser type for this formulation.

The lure was evaluated in a research grain store and in a range of commercial premises (a maltings, a flour mill, a grain store and an import/export warehouse) over a six-week period in both PCT traps and PCT floor traps.  There were some significant increases in insect numbers caught in traps with the lure, particularly for the rust red grain beetle, but in general these were small.

This project made significant progress towards the development of a food-based multi-species lure and in developing techniques to examine release rates. Further refinement and validation is required prior to commercialisation.  Optimisation of monitoring methods will provide more effective detection and interpretation, enabling strategic application of control measures and reduction in pesticide usage.