Lending fresh air to grain pest problem

June 01, 2015

Wheat growers are excited by early data from an on-farm experiment to assess a non-chemical method of reducing insect damage in stored cereal grain.

The study is led by the Plant Biosecurity CRC, partnering with the Western Australian grower collective Mingenew-Irwin Group (MIG), and is part of the CRC’s program to find solutions to a global problem in the wheat industry that has intensified during the past decade – phosphine resistance. Phosphine is the industrial fumigant most widely used worldwide to kill and control beetles and weevils in stored grains, but its effectiveness is declining due to the development of resistance.

Former-owned and independent research company Kondinin Group has been engaged to trial an alternative practice called aeration. It’s been around as a concept for a long time but is not widely adopted. It requires cool, dry air to be pumped into stored grain. The CRC study has shown that this can be done simply and economically – and that it works.

“I think it’s pretty exciting in terms of looking for options and alternatives as well as supplementary solutions to combating insects in grain storage,” said Kondinin Group research manager and agricultural engineer Ben White, who has been running the experiment.

White and his team have been testing a simple set-up on 70 tonne cone-bottom silos – the typical type used throughout WA’s wheat belt. At the base of the silo, they place a 550 watt centrifugal fan that’s switched on and off according to ambient humidity and temperature as measured by an aeration controller mounted nearby. The conditions that cause the fan to switch on are determined by simple algorithms, one of which was developed many years ago and licensed by the CSIRO.

The aim is to only run the fans when ambient humidity is below 80%. If air temperature and humidity levels are suitable, air is pumped through the stored grain at the rate of 2–3 L per second, per tonne, which cools the grain. While this doesn’t kill insects, it reduces their activity significantly and creates conditions in which they are unable to breed.

Another benefit identified by the Kondinin trial is that aeration reduces proportions of non-sprouting grains. Aeration has been shown to produce a net benefit of over $2 per tonne, which is $140 per silo, and pays for the aeration system within a year. This is in addition to the other potential savings from reducing or eliminating phosphine use.

Sheila Charlesworth, executive officer for MIG, says the study proves there are economic benefits to aeration, and her growers intend to implement it. In addition, growers from NSW and Queensland who travelled to WA to observe the method have since adopted it in their home states.

– Karen McGhee


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