Resistance on the rise in storage insects

Colour illustration of an adult Flat grain beetle - Image copyright DEGESCH America, Inc.
Adult flat grain beetle.

Grain storage entomologists are closely monitoring resistance of insects to the fumigant phosphine and are advising growers and grain handlers to review their control practices. Some growers have had recent grain loads rejected due to unacceptable infestations.

The frequency of resistance of grain insects to phosphine fumigant has steadily increased in all species since the mid-1990s. The lesser grain borer, the rust-red flour beetle, the saw-toothed grain beetle and more recently the flat grain beetle have all developed some form of resistance to the fumigant.

Scientists lead a national resistance monitoring program which provides information on the presence of and trends in resistance to phosphine and assists grain handlers by providing information on managing resistance and control options.

Through extensive laboratory work and field trials scientists now understand the concentrations and exposure periods required to control the insects. 

Grain handlers and growers can achieve reduced storage pest numbers through careful attention to equipment hygiene combined with well managed cooling aeration. This reduces the number of fumigations required. However when a fumigation is required, use a well-sealed silo and accurately follow the label rates to achieve the best results.

In case of an outbreak of flat grain beetles, send samples to Primary Industries and Fisheries for resistance testing (phone Manoj Nayak on 07 3896 9431 or Phillip Burril on 07 4660 3620 for further advice).

Further information

Last updated 31 March 2009