Plan for stored grain insects

There is a nil tolerance for live stored grain pests at grain receival sites; planning for the control of these pests is an absolute must!

Stored insect pests take advantage of grain spills around silos (source: grower)

Imagine, after a big season of battling the elements and finally seeing your grain dispatched to the receival sites, you get a call saying it’s been returned because of pest contamination. Below is a reminder of how to best manage post-harvest grain pests.  Some keys elements to minimising infestation risk are:

1. Good hygiene in and around storage systems

Employing good hygiene practices is a crucial step in managing and controlling stored grain insects. These include:

• Cleaning up grain residues and spillages in and around storage facilities and machinery, and removing weeds and rubbish

• Thoroughly cleaning grain residues and applying structural treatments* (e.g. diatomaceous earth) on harvest machinery and equipment including headers, augers, chaser bins, field bins, and silos.

(*Avoid using for pulses and oilseeds. Be aware of withholding periods if you are treating the inside of an empty silo with a registered insecticide.)

2. Monitoring and correct identification of insect species

Monthly monitoring will provide an indication of whether the grain will meet receival standards, and the opportunity to correctly identify any pests that are present. There are many damaging insect pests of stored grain including the lesser grain borer (Rhyzopertha dominica), the saw toothed grain beetle (Oryzaephilus surinamensis), the flat grain beetle (Cryptolestes spp.) and the rust red flour beetle (Tribolium castaneum). There are many other beetles, moths and mites that can also be pests of stored grain. Correct insect identification will allow for more targeted control options, and minimise the likelihood of control failures due to insecticide resistance (which is present in multiple species). The GRDC Fact Sheet Stored grain pests – Identification will assist.

The lesser grain borer has developed resistance to phosphine (Source: GRDC)

 

3. Ensuring silos are gas-tight

Phosphine fumigation is one of the most commonly used techniques for protecting grain. However, the widespread use of phosphine has led to the development of resistance. The best approach to manage chemical resistance is to ensure phosphine is only used when necessary and fumigation takes place in gas-tight storages. Phosphine should be held at lethal concentrations for 7-10 days to ensure effective control of all insect life stages. Silos that will be fumigated should have their seals checked and be pressure-tested to ensure they are gas-tight.

4. Cooling aeration facilities

Consider installing aeration cooling fans and aeration controllers to facilitate circulation of cool, dry air through the grain. When grain temperatures are kept below 20°C, insect development is reduced. Below 15°C most insect breeding will be minimal or cease altogether.

Further information on managing stored grain pests can be found on the GRDC Stored Grain Supplement video series and the following grain storage factsheets:

Hygiene and structural treatments for grain storages

Grain storage pest control guide

Aeration cooling for pest control