Northern and Southern regions

Stored grain pests — identification

CAUTION: RESEARCH ON UNREGISTERED PESTICIDE USE
Any research with unregistered pesticides or of unregistered products reported in this document does not constitute a recommendation for that particular use by the authors or the authors' organisations. All pesticide applications must accord with the currently registered label for that particular pesticide, crop, pest and region.

 

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KEY POINTS

  • Avoid surprises when selling stored grain by monitoring for insect pests monthly.
  • Correct insect identification will allow for more targeted pest control options.
  • Sample from the top and bottom of grain stores for early pest detection.
  • Warming an insect sieve in the sunlight will encourage insect movement, making pests easier to see.
  • Exotic pests are a threat to the Australian grains industry — report sightings immediately.

Why is identification important?

 

In a deregulated grain market, on-farm storage is now more popular then ever before. But finding insects crawling up the sides of your grain hopper while loading a truck is frustrating and costly to manage. Regular monitoring and correct pest identification are the first steps to ensure delivery of insect-free grain to market.

Being able to identify the most common insect pests of stored grain puts growers well ahead when it comes to making the best control decisions. For example, the lesser grain borer is a serious pest in most regions of Australia, but can now only be reliably controlled with one or two products due to resistance. So if growers intend applying control treatments they need to know which species are present.

Identification of the particular pest present can highlight a future preventative measure. For example, psocids thrive in warm, humid conditions. Using aeration to lower grain temperature and storing grain at a lower moisture content could prevent a future problem from occurring.

With an increasing number of grain markets requesting reduced chemical residues on grain it is becoming more important to better identify and understand pests. In doing so growers can exploit the best use of both chemical and non-chemical control measures. As there are limited tools available to control pests in stored oilseeds and pulses, meticulous hygiene, well-managed aeration and regular monitoring is essential.

Key pest species

Cereal grains include wheat, barley, oats, triticale, sorghum and maize.
The most common insect pests of stored cereal grains in Australia are:

  • Weevils: (Sitophilus spp.) Rice weevil is the most common weevil found in wheat in Australia
  • Lesser grain borer: (Rhyzopertha dominica)
  • Rust-red flour beetle: (Tribolium spp.)
  • Saw-toothed grain beetle: (Oryzaephilus spp.)
  • Flat grain beetle: (Cryptolestes spp.)
  • Indian meal moth: (Plodia interpunctella)
  • Angoumois grain moth: (Sitotroga cerealella)

Identification of common beetle pests of stored grain

 

Exotic pests – be on the lookout forAnother dozen or so beetles, psocids (booklice) and mites are sometimes present as pests in stored cereal grain. Oilseeds include canola, linseed, safflower, cottonseed and sunflower. The most common pests in stored oilseeds are:

  • Flour beetles
  • Saw-toothed grain beetles
  • Moths

Resistance

The lesser grain borer and saw-toothed grain beetle have developed resistance to a number of grain insecticides. Poor fumigation practices (such as unsealed silos) have also increased the number of phosphine-resistant stored grain pests. Such resistance can threaten grain exports, as live insects remain in grain after fumigation. If insects survive fumigation, contact your regional grain storage specialist. See contact details on page 4.

Monitoring information

To maintain grain quality and to select the correct treatments, identify pests early by sampling monthly. Sieving is the most effective method of detecting grain pests. Sieve samples from the top and bottom of stores to detect low levels of insects early. Sieving samples onto a white tray will make it easier to see small insects. Holding the tray in the sunlight warms the insects and encourages movement making it easier to identify them and monitor population numbers.

To maintain grain quality and to select the correct treatments, identify pests early by sampling monthly.

Grain pest identification

A clean glass container helps to identify grain pests. Place the live insects into a warm glass container (above 20°C so they are active, but not hot or they will die). Weevils and saw-toothed grain beetles can walk up the walls of the glass easily, but flour beetles and lesser grain borer cannot. Look closely at the insects walking up the glass — weevils have a curved snout at the front but saw-toothed grain beetles do not.

Useful resources:

Grain storage specialists

Grain biosecurity contacts

Acknowledgements: Philip Burrill, DEEDI, Peter Botta, PCB Consulting, Chris Newman, DAFWA.

Disclaimer:
Any recommendations, suggestions or opinions contained in this publication do not necessarily represent the policy or views of the Grains Research and Development Corporation. No person should act on the basis of the contents of this publication without first obtaining specific, independent professional advice. The Corporation and contributors to this Fact Sheet may identify products by proprietary or trade names to help readers identify particular types of products. We do not endorse or recommend the products of any manufacturer referred to. Other products may perform as well as or better than those specifically referred to. The GRDC will not be liable for any loss, damage, cost or expense incurred or arising by reason of any person using or relying on the information in this publication.

CAUTION: RESEARCH ON UNREGISTERED PESTICIDE USE
Any research with unregistered pesticides or of unregistered products reported in this document does not constitute a recommendation for that particular use by the authors or the authors' organisations. All pesticide applications must accord with the currently registered label for that particular pesticide, crop, pest and region.