Farm Management

Grain protectants build barrier against storage pests

Harvesting grain: Image: Chris Stacey

Growers planning to store grain in unsealed storages after 2016’s harvest are being encouraged to consider using grain protectants to reduce the risk of insect pest infestations.

The use of protectants combined with meticulous hygiene and aeration cooling are especially useful in storages which are not gas-tight and therefore cannot be fumigated effectively.

Grain storage specialist for the southern cropping region, Peter Botta, says grain protectants are designed to prevent pest infestations – not to control existing infestations.

“A common misunderstanding is that grain protectants kill insects already infesting the grain, but those types of products (contact disinfestants) are no longer available for on-farm use,” says Mr Botta, whose work is supported by the Grains Research and Development Corporation (GRDC).

“Therefore, grain must be clean and free of pests before applying a protectant.”

In order to give protectants the best chance to defend stored grain, meticulous storage hygiene practices before and after harvest are required.

Mr Botta says cleaning storage sites and harvesting equipment removes harbours where pests can survive, ready to infest the new season’s grain. The addition of aeration cooling also provides an unattractive environment for pests in stored grain.

He reminds growers to always read the chemical label before choosing a protectant to ensure it is registered for use on the grain to which they intend to apply the product and that it will target the main insects commonly found in their storage.

As a general guide, protectants are only registered for use on cereal grains and only some (not all) of those protectant products are registered for use on malting barley, rice and maize. No protectants are registered for use on pulses and oilseeds.

Before considering application of a grain protectant, Mr Botta implores growers to fully understand the requirements of the targeted markets for their grain.

“Some buyers – domestic and overseas – will not take grain that has had protectants applied, so it is critical that growers know in advance what those market specifications are so they aren’t limiting their selling options,” he says.

If targeting markets which accept grain that has been treated with a protectant, knowing the maximum residue limits (MRLs) of those markets is also essential.

“As grain markets have become less tolerant to protectants and maximum residue limits (MRLs) are monitored scrupulously, accurate application in terms of the correct rate and spread is vital.”

Commodity vendor declarations are also used in many cases to ensure a parcel of grain is only subjected to one application of the protectant to avoid exceeding the MRL.

Some protectants start deteriorating 48 hours after being mixed with water so growers should avoid leaving prepared protectants for long periods before applying to grain. The product label will also indicate the anticipated effective life of the protectant on the grain.

The effective life of protectants is shortened if applied to grain above 12 per cent moisture content and at temperatures above 27°C, or if treated grain is exposed to direct sunlight which can occur at the end of a shed or in an open bunker.

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