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What to keep an eye on

Cereal aphids have been a major concern for many growers this spring. Heavy infestations have been observed across a large number of cereal crops. Feeding damage and potential yield losses from cereal aphids will depend on many factors. Losses are generally more severe when crops are moisture stressed, whereas sufficient moisture availability may enable crops to withstand moderate-high aphid populations with little or no yield penalty. Although weather conditions over the next month are likely to favour aphid development, numbers are likely to naturally decline in many regions. The combination of declining suitability of cereal plants as crops mature and increasing beneficial insect activity will often result in cereal aphid populations crashing.


Snails can cause contamination issues in grain when they are present above cutting height in the canopy (or in windrows) and harvested along with the grain. This can lead to clogging of machinery and/or quality downgrades. A series of wet winters and moist summers have resulted in snail numbers increasing in many regions of Victoria and New South Wales. Harvester modifications and grain cleaning will help to ensure grain is successfully delivered, but these usually incur some grain wastage. Identifying snail species and monitoring numbers before harvest, and before and after control operations is essential. For further information refer to GRDC FactSheet – Snail Management.

Rutherglen bugs (Nysius vinitor) are native insects that attack a wide range of weeds and crops. They are well adapted to dry warm weather and are often most damaging to moisture stressed plants. Adults can also become a grain contaminant when in high numbers. Highest numbers of Rutherglen bugs are often observed along crop perimeters or in heavily weeded areas of crop. Numbers will increase with the warmer weather conditions as weeds dry off, forcing the insects to move up to the upper crop canopy or to fly into crops. They can reach damaging levels very quickly. Check crops over the coming weeks, particularly canola, linseed and sunflowers. Click here for images of Rutherglen bugs.


Stored grain insects can be a serious threat to grain storage. Unfortunately the widespread use of phosphine has led to the development of resistance in several insect pests of stored grain. Correct insect identification will allow for more targeted control options, and minimise the likelihood of control failures due to resistance. The best approach to manage chemical resistance is to ensure phosphine is only used when necessary and fumigation takes place in rigorously maintained gas-tight storages. Phosphine should be held at lethal concentrations for 7-10 days to ensure effective control of all insect life stages.

The following steps are recommended in order to minimise problems that can reduce grain quality in storage:

  • Clean up grain residues and spillages in and around empty storage facilities and machinery.
  • Ensure insect pests are not carried onto your property on farm machinery.
  • Silos that will be fumigated should have their seals checked prior to filling to ensure they are gas-tight.
  • Install aeration cooling fans and aeration controllers.
  • Monitor grain monthly for insects, grain temperature and moisture.
  • Grain that is to be stored for more than 6 weeks should generally be treated with an insecticide.

For further information on grain storage pests, including monitoring and management refer to GRDC FactSheet - Stored Grains Pests or visit

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