Grain growers are being encouraged to ensure storage silos have a 'clean bill of health' as attention turns to winter crop harvest.
The advice comes from the GRDC Grain Storage Extension team. GRDC has a long-standing investment in on-farm grain storage and extension to support best practice management to growers.
GRDC Grain Storage Extension team project lead Chris Warrick said the biggest challenge of storing grain is dealing with insects (weevils) - and prevention is always better than cure.
"Controlling insects once they infest grain requires fumigation or controlled atmosphere, both of which require gas-tight, sealable storage. For un-sealable storage, prevention is our only option (short of transferring grain into gas-tight sealable storage for batch fumigation)," he said.
"Hygiene is the first line of defence and goes beyond just the storage area and its surroundings. Whole-farm hygiene includes cleaning any equipment that handles or holds grain, such as stock feeding equipment.
"Waste grain should be disposed of by feeding it to stock, burying it, or spreading it out thinly over the ground to decompose. A pile or drum of waste grain creates the perfect breeding ground for insects, undoing all our hard work in cleaning up."
Once the clean-up is complete, Mr Warrick said storage and equipment can be treated with diatomaceous earth (DE) to ensure there are no surviving insects left to reinfest newly harvested grain.
"Recent testing revealed that an 18-volt battery or petrol-powered leaf blower can effectively distribute the DE throughout a cone or flat bottom silo from ground level. A venturi gun on a standard air compressor can also be used, though it was less effective in the tests."
The next step is to use protectants as an additional insect prevention tool for cereal grain.
Mr Warrick noted that because some markets, especially international buyers, require Pesticide Residue Free (PRF) grain, protectants are best suited to domestic, feed cereals in un-sealable storage, where fumigation is not an option.
"In Western Australia, product choice is limited, while in other states, it can be simplified to two decisions," he said.
"A registered grain storage protectant with the active ingredients Spinosad and S-methoprene or Deltamethrin and Piperonyl butoxide should be rotated every year or two. However, if the lesser grain borer is present on the property, Spinosad offers higher efficacy - highlighting the importance of accurate insect identification."
Mr Warrick said the second decision is to select a mixing partner with an active ingredient of Fenitrothion or Chlorpyrifos-methyl, provided neither one is already included with the Spinosad or Deltamethrin.
"The mixing partner offers protection against rice weevil and growers should consider the type of grain being stored, the withholding period, and market acceptance when making this choice," he said.
"Fenitrothion is registered for a broader range of cereals but requires a 90-day withholding period when applied at the nine-month protection rate. Chlorpyrifos-methyl has no withholding period; however, it is not registered for malt barley or rice and is accepted by fewer markets. Always read and follow label directions."
Mr Warrick said aeration cooling is the other key component of insect prevention.
"By cooling grain, insect activity can be slowed or even stopped if low enough grain temperatures are achieved."
"Additional benefits of aeration cooling include preventing mould growth, temporarily holding over moisture grain until it can be dried, blended, or fed to stock, and reducing the vent time needed to clear gas after fumigation."
Aeration cooling can be retrofitted relatively easily to cone bottom silos and operates most efficiently with an automatic controller. Aeration systems should be selected with the goal of delivering two to three litres of air per second per tonne, tailored to the type of grain being stored.
"Recent testing showed that it is beneficial to inform aeration equipment suppliers about the specific grains being stored to ensure the fan can handle the backpressure caused by the grain type," he said.
"Suppliers should also be asked whether their quoted airflow rates are based on calculations or actual field tests, as instances have shown that aeration system performance in real-world conditions can be significantly lower than the supplier's calculated estimates."
Mr Warrick said that monitoring grain temperature and regularly checking for insects are also essential steps in preventing issues in stored grain.
"This can be done with simple probe traps and thermometers inserted into the top of the grain stack," he said.
"Access ports can be installed on the sides of storages to obtain readings throughout the stack, and remote monitoring equipment can be added to provide real-time readings directly to a dashboard or mobile device."
Pre-harvest health check top tips:
- Hygiene is the first defence and extends beyond the storage and surrounds, including all equipment that handles grain
- Post cleaning, apply DE to address any remaining insects
- Consider protectants as an additional insect prevention tool
- Make use of aeration cooling for multiple benefits
- Monitor regularly for pests.
An online GRDC Grains Research Update webinar was recently held on the topic. The recording can be viewed via the GRDC website.
