CRC30064: Resistance management of stored grain insects in the southern region

Resistance in grain storage insects to chemical treatments continues to be a problem throughout the southern region. Regional surveys have detected new sites of strong phosphine resistance, with only a few recurrences at previous sites (generally central storages).

Research outcomes

High levels of resistance to phosphine were detected in the flat grain beetle and lesser grain borer in the southern region.

The regional surveys found new sites of strong phosphine resistance which tended to be associated with the storage of grain in unsealed structures.

Levels of resistance to phosphine now being detected in flat grain beetles cannot be controlled with current protocols and threaten management of this insect both on farm and in central storages. This will place increasing pressure on protectant insecticides such as methoprene and deltamethrin and further control failures are predicted throughout NSW, Victoria and South Australia.

Research implications

If resistance to phosphine continues to develop at the rate recently detected in the flat grain beetle, then alternative chemical treatment will be required.

Furthermore, recent changes to the phosphine label state that it is restricted to use in “well-sealed structures” which will further limit accessibility as many farms do not have these structures.

Any new chemical treatments that may be developed will invariably be more expensive than phosphine and are also likely to require added infrastructure costs for application.

However without alternative treatments it is probable that further control failures will occur which will place increasing pressure on the ability of Australia to maintain competitive advantage based on insect-free grain.

To prolong the use of phosphine in the interim period it is recommended that an education and training program be developed for the use and application of phosphine.

This will assist the grain storage industry with an understanding of appropriate and optimal chemical application and fumigation procedures.

Acknowledgements

The NSW Department of Primary Industries would like to acknowledge the following organisations for supporting the project:

• Cooperative Research Centre for National Plant Biosecurity
• Grains Research and Development Corporation
• GrainCorp
• ABB Grain
• NSW Department of Primary Industries