Integrated use of pesticides in grain storage in the humid tropics

Severe losses of grain between harvest and consumption in Southeast Asia have caused considerable concern, because of both loss of commodity and deterioration of quality. Insects are a major cause and, although considerable resources have been diverted to preventing such losses, it has become obvious that use of pesticides is essential. Australia leads the world in development of grain protectants, insecticides incorporated into the stored grain mass. It is desirable that technology already developed in Australia be transferred to Southeast Asia and that capability for further country-specific development be established.

The project follows on from two closely related ones - 8309 and 8311 - covering the same topic, both considered relevant to existing and emerging regional problems. It will operate in Australia, Malaysia and the Philippines (as did its predecessors) and also in China and Thailand. It will have a commodity balance of 70% rice, 20% maize and 10% legumes.

The team in Queensland will conduct basic studies on the performance of grain protectants and fabric treatments including insect-growth regulators at high grain moisture/relative humidity levels, and on how synergists affect the activity of synthetic pyrethroid insecticides. They will also study the comparative efficacy of grain protectants on a range of commodities, and develop theories to describe these behaviours. These data will suggest minimum effective doses for candidate grain protectants. Parallel studies on the kinetics of decay of the pesticides will be carried out in collaboration with the CSIRO Stored Grain Research Laboratory.

Other research teams will carry out field trials in their respective countries. Surveys of the pesticide-resistant status of major pest species in the region and establishment of typical strains in laboratory culture will contribute to verification of minimum effective doses on local commodity varieties. Later field trials will involve treatment of building fabrics, bag stacks and grain bulks in commercial storages using treatments and application rates suggested by the basic studies. Grain samples will be bioassayed (and residues determined analytically) by the regional teams.

Together with its two predecessors, this project will confer major benefits. It will develop systems of integrated use of pesticides to reduce losses during storage of commodities of high moisture content in humid tropical environments. Acquisition of a basic understanding of how grain moisture and grain species influence the biological activity and residual behaviour of the pesticides in stored grain (together with the local capability to design and conduct proving trials for new materials and techniques) will allow future development. The technology will be applicable throughout the grain storage sectors in China, Malaysia, the Philippines and Thailand, particularly in central handling systems, but also in the cooperatives and village stores and, if necessary, on farms. And it will be relevant to other countries in the region, providing systems for control of pests that should be acceptable both locally and in international trade.

The technology will be equally relevant in Australia's north particularly for commodities such as maize and legumes, where production is increasing due to crop diversification but has not yet reached levels that warrant high priorities for research attention.