Fumigant resistance: small victories in an unrelenting battle

As insect resistance to phosphine continues to climb across both on-farm and bulk storage, growers face a constant challenge: how to slow resistance while protecting grain quality and market access. Recent GRDC-supported resistance monitoring shows a slight dip in strong phosphine resistance this year, but the overall national trend remains upward, with about 30 per cent of pests now showing strong resistance—well above the 10–15 per cent level considered manageable.

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Phosphine Best Management Practices: Disinfesting stored commodities

Phosphine remains the most widely used fumigant in Australia’s grain industry due to its effectiveness, low cost, and residue-free status. However, increasing resistance among key insect pests highlights the need for strict adherence to best practice guidelines.

This comprehensive manual outlines:
1. Proper application methods across different storage types (silos, bunkers, sheds)
2. Critical factors such as gas concentration, exposure time, temperature, and moisture
3. Equipment for monitoring gas levels and ensuring safe fumigant handling
4. Strategies to delay and manage resistance, including use of sulfuryl fluoride and integrated pest management

Compiled by leading experts including Dr Manoj Nayak, Dr Joanne Holloway, Chris Warrick, and Patrick Wilson, this document is a valuable resource for growers, storage operators, and advisors working to maintain grain quality and market access.

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