Stored grain pests

With harvest time approaching it is timely to think about storing grain on farm.  Harvested grain is at its highest quality when it is first loaded into storage. If the storage environment is not managed correctly the quality will steadily deteriorate. To ensure success, the need for careful planning is essential. Grain insects, end-user requirements and maintaining quality are important issues to consider.

Grain storage expert, Peter Botta (Victoria DPI), says one of the most important things for growers to understand is the markets they wish to supply and their requirements. This takes careful planning and could mean improving storage facilities. Markets are increasingly demanding grain free of chemical residues. In sealed storage, grain can be fumigated effectively, providing quick, inexpensive and long-lasting insect control without the problem of pesticide residues.

Generally, grain to be stored for more than six weeks should be treated. Grain can be treated with a protectant when it is added to storage or fumigated in a sealed silo. Most contact protectants give between 3-6 months protection, although this is dependent upon the moisture content and temperature of the grain. Too high moisture content and temperatures can lead to the rapid breakdown of protectants and leave grain vulnerable to attack. Always aim to store grain at a moisture content of 12% or less and at a temperature of 25°C or less. This will also help to limit the activity of insects and avoid grain spoilage from moulds and fungi.

There are many damaging stored grain pests. Some of the most important include the lesser grain borer (Rhyzopertha dominica), the rice weevil (Sitophilus oryzae), the saw toothed grain beetle (Oryzaephilus surinamensis) and the rust red flour beetle (Tribolium casteneum). These are all small (between 2-3 mm long) and dark reddish-brown to grey in colour. Check for these pests in grain residues in harvesting and grain-handling equipment, and in storages.

Peter says prevention is better than a cure. Seals on silos should be checked before each filling and replaced if worn or damaged. Headers, grain handling equipment and storages should be thoroughly cleaned down after use. Clean up spillages in areas around silos and destroy all residues to prevent re-infestation.

For further information on stored grain issues click here, or contact Peter Botta (Victoria DPI) on (03) 57611647 or by email: peter.botta@dpi.vic.gov.au.