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Treat Grain Nicely This Festive Season

07 December 2011

AUSTRALIA - When it comes to controlling pests in stored grain this season, growers can choose both chemical and non-chemical treatment options. Usually a combination is best.

The Grains Research and Development Corporation (GRDC) is eager to point out to farmers that modes of action for grain pests depend on individual needs and circumstances, and there are some easy ways to decide.

Indeed, Agri-Science Queensland grain storage specialist Philip Burrill says for grain storage, three key factors provide significant gains for both grain storage pest control and grain quality – hygiene, aeration cooling and correct fumigation.

"In particular, I can’t emphasise enough how effective hygiene can be, particularly knowing how rapidly insects multiply and spread from a small amount of old residual grain under warm spring and summer conditions,” Mr Burrill said.

“By ensuring that machinery and equipment used to handle grain, including headers, augers, field bins, truck bins, silos and other storages are clean to prevent insect pest contamination of newly harvested grain you have a huge head start.

“It’s also important to check or clean out left-over planting seed, empty silos, feed troughs, shed floors, old bags of seed gradings or any other sheltered food source where insects may multiply.”

Once storages and equipment is clean, you may also consider treating the surfaces with Diatomaceous earth (DE) e.g. Dryacide®.

DE is low in toxicity to humans and animals, effective longer term and free of chemical residues. It can be applied as a dust or slurry, and if applied correctly it can provide up to 12 months protection.

“Once your grain is in storage, there are other activities you can undertake to protect your grain from pests and maintain quality,” Mr Burrill said.

His colleague in grain storage, Peter Botta says the other thing to remember is that aeration cooling can greatly reduce insect and mould activity in stored grain, as well as preserve grain quality.

Grain is an effective insulator and without aeration it will maintain its warm harvest temperature in storage (often around 30ºC) for a long time.

“By rapidly reducing the temperature of the grain after harvest you can limit chances of grain pest problems. While adult pests can survive cool grain temperatures, most young stages of the storage pests stop developing at temperatures below 18 - 20°C,” Mr Botta said.

“Well controlled aeration cooling in combination with good hygiene will mean that, in some years, fumigation for pests may not be required. However fumigation is often required in years where grain has slightly higher moisture content, and conditions are warm and humid.”

Non -Chemical Treatments

  • Meticulous grain hygiene
  • Well managed aeration cooling
  • Regular, monthly monitoring

Simple! Done together these non - chemical treatment options will overcome the majority of storage pest problems.

Chemical Treatments

  • Fumigation with phosphine is a common component of many integrated pest control strategies
  • Fumigation must be done in a sealable, gas-tight silo to be effective
  • Mr Botta says if you need to fumigate grain there are several things to be aware of.

“The most important step towards effective fumigation is to have the correct storage facility. Fumigants such as phosphine should only ever be used in a gas-tight, sealable silo,” he said.

“Using phosphine in anything less won’t achieve a high enough concentration of chemical for long enough to kill all life stages of the pests. The pest will quickly reappear in grain where phosphine is used in unsealed storages."

Effective fumigation requires a minimum of 300 parts per million (ppm) phosphine gas concentration for seven days or 200ppm for 10 days.

If you have leaks in your silo, you won’t be able to achieve those levels. It is very important that you pressure test your silo at least once a year to ensure that your silo is still gas-tight.

“In regards to applying protectant insecticides to grain, a number of grain buyers are now requiring that grain and grain products have nil chemical residues, so you should always check with potential buyers and handlers before you treat with commercially available products such as Fenitrothion, Reldan, and IGR.

“Do not use any of these chemical insecticides when storing oilseeds or pulses. However there continues to be an important role for grain chemical treatments. Always check labels," Mr Botta said.

“By being mindful of all the points discussed grain storage can be a very positive boon for both growers, and national grain quality. All it takes is a little care.

TheCropSite News Desk

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