Integrating grain protectants into storage pest management

• Chengdu Grain Storage Research Institute, China
• Ministry of Commerce, China

The amount of grainboth domestic and importedentering trade channels in China has more than doubled in recent years. This has placed considerable pressure on the traditional postharvest handling and storage sector, which has not kept pace with developments in production. The inability to handle and store grains safely has led to increasing losses in whole grain and grain quality.

Insect pest activityparticularly if grain is held for extended periodsis the most important impediment to the maintenance of grain quality. This is a worldwide problem, and Australia has led the world for many years in development of technology for reducing such losses. The most widely used and effective weapons are insecticides. These must be approved for use as grain protectants and used according to well-defined protocols. Pests easily develop resistance to them; and they leave chemical residues, which can persist through to the end-use foodstuff. Until it is possible to phase them out, protectants must be used as effectively as possible, and their use must be minimised through their close integration into storage pest-management strategies.

This project follows a request from various institutions in China for Australian collaboration in order to gain expertise in grain-storage technology. The area of study has been given high priority by the Ministry of Commerce (MOC), which has centralised control of the grain industries in China. The Queensland Department of Primary Industries (QDPI), which coordinates an Australia-wide Working Party on Grain Protectants, has been commissioned by ACIAR to lead the project. The Working Party has close links with the Australian Wheat Board, CSIRO, universities, other departments of agriculture and the grain and pesticide industries. Chinese collaborators are scientists from the Chengdu Grain Storage Research Institute, the main institution for postharvest research on grain in China and part of the established network for transferring technology into practical use throughout the country.

Research objectives are to:

. develop general models of pest-management decision making and modify these for specific grains and storage systems;
. define relationships between control measures, physical components, pest population growth and commodity damage;
. use models to evaluate pest-management strategies, particularly protectant use, in achieving required levels of pest control; and
. develop decision-support systems as components of expert systems integrating all components of pest-management and storage systems.

Research teams in each country will be responsible for trial work in their respective countries. Communication will be facilitated by exchange visits between the two countries of key project personnel.

In Australia, existing models and expert systems will be adapted and expanded for use in this project. Sophisticated simulation models of biological, physical and chemical processes will be incorporated. The effect of sub-lethal doses of grain protectants on the subsequent growth of pest populations in storages in warm climates will be studied, and laboratory studies will be carried out on key species, including Sitophilus zeamais, which is significant in the storage of maize and rice in warm climates. The expert systems for the rice, maize and wheat will be evaluated.

Chinese collaborators will report in detail on the grain industry in China, and pest problems there. They will also collaborate in developing models, parallel to the ones developed in Australia, relating infestation levels and commodity losses to pest-management options, as a basis for expert systems to guide decision-making for pest management. Chinese work will also include surveys for insecticide resistance, acute toxicity testing of candidate grain protectants, assays for determination of minimum effective doses of insecticides for Chinese pest strains, field trials, and field evaluation of pest-management strategies in the Chinese grain storage system.

China produces about 400 million tonnes of grain annuallyabout 40% of the gross value of agricultural production in that country. China also imports 713 million tonnes of wheat annually, mainly from Australia. Even an extremely small positive effect on storage losses of grain would give a 10% rate of return over 20 years from the total expenditure on this project (from ACIAR and other sources). As a result of minimised use of protectants, consumers will benefit from reduced chemical residue levels, and the development of insect resistance will be slowed. Direct benefits to Australia include the development of an expert system for incorporating grain protectants into storage management systems for Australian wheat, maize and rice. Indirect effects may include enhanced trade with China.