Silos that allow efficient aeration are essential for maintaining grain quality in on-farm storage.
PHOTO: Tom Dixon
With its hot, humid climate, summer rains, and double cropping season, the northern grains region differs from other parts of Australia in its variety of storage pests. This makes grains storage decisions particularly crucial.
“As we have both summer and winter harvests, and most growers hold their own planting seed, there is rarely a time when growers have no grain being held on-farm,” says senior development agronomist with the Queensland Department of Agriculture, Fisheries and Forestry (DAFF) Philip Burrill.
A National Grain Storage Extension project, funded by the GRDC, is working towards making decisions easier for growers about which storage methods are best for different circumstances, which pests to watch out for, and how best to store grain in different regions.
Chemical treatments are less accepted in today’s marketplace and are also becoming less effective at controlling storage pests due to the development of resistance. An integrated pest management (IPM) approach to storage can help growers reduce their dependence on chemicals.
Mr Burrill says there are three essential steps to ensuring an IPM approach is successful. These include the regular monitoring and recording of insects, hygiene and aeration.
“All of these steps are non-chemical, which is very attractive for the expanding international grain market for pesticide-residue-free food crops, and this has been well demonstrated by growers in many districts,” he says.
Effective grain hygiene and aeration cooling can overcome 85 per cent of pest problems, but these methods require vigilance.
If a grower is planning to store grain on their property it has to be done correctly. Consultant Chris Warrick, who leads the extension project, says that only then will the benefits outweigh the time and money invested.
“When you actually put a figure on it, the costs of good monitoring, hygiene and aeration are less than a dollar per tonne each,” he says. “Such a cost is really insignificant and can provide huge benefits.”
Knowing your enemy
An increasing number of grain markets are requesting reduced chemical residues in grain. It is therefore more important than ever for growers to be able to identify and understand storage pests and exploit the best aspects of both chemical and non-chemical controls.
There are six common grain storage pests normally seen on farms in the northern region. These include the lesser grain borer, rust-red flour beetle, rice weevil, saw-toothed grain beetle, flat grain beetle and psocids. The lesser grain borer and saw-toothed grain beetle have developed resistance to several grain insecticides.
“Normally, when we’re sieving we can see anywhere between two to three, possibly four, species of these main pests,” Mr Burrill says. “It would be rare for us to go to a farm and not detect them.
“In fact, we’ve only ever found one farm without any, which was amazing. But that grower is absolutely meticulous with hygiene and aeration, and so far we haven’t trapped any live insects from his silos. That’s unusual, but it shows that, with a bit of effort, you can minimise pest numbers.”
Hygiene and aeration
Growers must establish regular, monthly storage check-ups and plan for one major clean-up each year, Mr Burrill says.
“Winter time is a brilliant hygiene time, especially mid-winter, because the insects are not keen to get out of the silo when it’s cool, so they’re not flying,” he says.
“As soon as you hit the warmer months, from August, the already-mated insects start heading out to look for fresh grain to infest. By doing the major clean-up in winter makes for a sensible outcome.”
The aeration cooling phase, however, should be all year round in the hot and humid north. Silos should never be closed up and left sealed for any period of time, Mr Burrill says, except during fumigation.
“In two days you can cool down your grain beautifully, by a minimum of 10°C, just by using aeration fans. Cooling makes life difficult for the insects, because they prefer a temperature of more than 30°C. At 20°C there will be no increase in the population of some pests.
“Monitoring, hygiene and aeration won’t solve all your problems, but growers who do these three things regularly and well, backed up by good records, will only need to fumigate for pests about once in every three years,” he says.
When insect infestations are detected, fumigation is the main go-to control measure, as spray-on products are not available in the market. Fumigation with phosphine is a common practice in many IPM control strategies.
The quality of a growers’ silo is crucial for successful fumigation, Mr Burrill says. “We ask growers to get a good-quality silo that meets the Australian Standard (AS 2628-2010) for gas-tight storage, is easy to clean and is aerated, with fans and ducting, so it can cool the grain.”
“When you’re doing your monthly checks and have detected pests you should seal the silo, fumigate for seven to 10 days, use the aeration fan to blow the gas out, and then return to normal aeration. That’s the way we’d like growers to store their grain.”
There are also options for retro-sealing older silos to meet the requirements of fumigation, although the cost can be significant and may include ongoing maintenance costs. Growers should also ensure the retro-seal contractor can guarantee the Australian Standard for sealed silos.
Hotline storage advice
A Stored Grain National Information Hotline (1800 weevil) has been established to support growers with grain storage investment and practice needs. Mr Warrick says growers choosing to store grain on-farm after this year’s harvest are encouraged to phone the hotline if they need assistance.
“We would prefer to get phone calls for advice on how to get it right now, rather than calls later in the year to fix disasters.”
Phil Burrill, Queensland DAFF,
0427 696 500,
(1800 933 845) will put growers in contact with their nearest grain storage specialist.
Information on all aspects of grain storage is available via the GRDC Stored Grain Information Hub: www.storedgrain.com.au
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