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Winter Watching A Winner for Stored Grain

28 June 2012
GRDC

AUSTRALIA - The Grains Research and Development Corporation (GRDC) is reminding grain growers to avoid nasty surprises when out-loading grain by monitoring for pests regularly. It says early detection and correct identification of grain pests reduces grain losses, allows time for fumigations and reduces insect spread to other storages.

Grain farmers may have eased off monitoring their stored grain this winter, but Department of Agriculture, Fisheries and Forestry Queensland grain storage specialist Philip Burrill says monitoring in winter is still important.

“If you don’t have aeration cooling set up, the core temperature of your grain is still warm, sitting at 25 - 30 degrees which is perfectly suitable for pests.

Department of Agriculture, Fisheries and Forestry Queensland grain storage specialist Philip Burrill says monitoring in winter is important.

“While it’s true that the cooler weather means grain can be cooler around the edges of the silo, as an excellent retainer of heat, your grain could still be harbouring insects in the middle. Even with aeration cooling grain pests are not killed, but the cold grain temperatures make the storage an unattractive home and most existing insects stop breeding.”

Studies have shown that rust-red flour beetles stop breeding at 20°C; the lesser grain borer at 18°C and below 15°C all storage the major pests stop breeding. Growers should therefore aim for grain temperatures of less than 15°C during winter through the use of aeration cooling.

Aeration, when it is well managed, provides growers with an effective tool to significantly reduce insect pest numbers in there storages. It has the additional advantages of preserving many grain quality attributes. Using a good quality auto controller to operate your aeration fans will improve the reliability aeration cooling.

However, Philip Burrill says to get into the habit throughout the year of checking your grain at least monthly. “It is a bit like checking under the bonnet of your vehicle. Forget it for too long and it is likely to be very costly.

“Grain pest and grain quality management requires regular monitoring, correct pest identification and early action.”

95 per cent of growers store grain of some form, whether it’s bulk grain for sale in 3-months' time, planting seed or stock feed. Many growers store between five and twenty tonnes of planting seed on farm between seasons.

“While this planting seed has quite high monetary value now, it also has the future value of potentially producing a well-established stand for your next crop.

“I know of a grower who didn’t look after his planting seed, instead having the local seed grader remove damaged grain and most of the weevils before planting time. He did a germination test which gave decent results, but soon realised after planting this seed that it had poor vigour, which resulted in a very poor strike. In this scenario, he had to replant large areas after buying in new seed.

“Regular checking of stored grain is fairly simple, and should really be a monthly practice for farmers during the year and as often as fortnightly in the warmer spring and summer conditions

Sieving is an effective way to monitor grain for pests.

“Sieving grain is the most effective method of detect pests, and this is best done using the proper insect sieve with 2 mm mesh. If safe to do so, take grain samples from both the top and bottom of your silos .This will provide you with a better chance of detect pests early.

“To retrieve a grain sample, use a bucket and where possible a grain probe. Sieving onto a white tray and standing out in the sunlight to encourage insect movement. This helps detect small insects quickly,” Mr Burrill said.

Another simple method, which can be used in conjunction with your monthly sieving, is to use an insect probe trap. This is pushed into the grain and left there, and pulled out each month to check for insects that have been trapped.

If you do find any insects it is very important that you identify them correctly so as to be able to treat the infestation effectively. Keep a basic magnifying glass and storage pest identification guide handy so you can identify the pest species.

As an additional aid for identification, put the contents of your sieve tray with the live insects in a clear glass jar. Of the most common pests, the rice weevils and saw-toothed grain beetles can easily walk up the walls of the glass. Flour beetles and the lesser grain borers cannot.

“To tell the difference between the rice weevil and saw-toothed grain beetle, inspect their heads carefully. Rice weevils have a long curved snout at the front and lesser grain borers do not.”

Philip Burrill says he can’t emphasise how important this identification step is.

“There are different treatments required for different pest species, particularly when it comes to chemicals. If you don’t identify the pest you don’t know which treatments are suitable. Some species have resistance to certain chemicals.

“In fact, the insect you have found may not even be a grain pest, but instead some random insect resting on the top of your grain. You wouldn’t want to fumigate the whole silo if it is not required. You need to know.”

GRDC has several comprehensive insect identification resources, including an insect identification Fact Sheet, a Pocket guide and a poster, all of which can be found here.

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