Whether storing harvested grain for future marketing or crop planting, key factors to consider are silo hygiene and aeration, insect and pest control, grain quality and economics.
WA is the only Australian state able to export its entire grain harvest without the use of contact insecticides.
Local research shows that correct grain storage hygiene and aeration practices can supress stored grain insects and pests and maintain grain quality to boost seed viability for subsequent crop plantings.
Grain residue in storage facilities needs to be removed, as it provides ideal breeding sites for grain pests. Only a handful of grain is enough to maintain a viable insect population.
The Department of Agriculture and Food, Western Australia (DAFWA) says treating silos with products such as diatomaceous earth (DE) dust (e.g. Dryacide®) before storing grain is valuable.
It suggests growers be aware of withholding periods if treating the inside of empty silos with an insecticide, such as Malathion dust/liquid, to provide residual control before grain is loaded into the store.
It is illegal to apply protectants other than Malathion and Dryacide® to grain in WA, except if it is to be used for seed.
Before storing grain, gas-tight sealable silos should also be tested for any gas leaks and pressure relief valves filled with light hydraulic oil.
For a silo to meet the Australian Standard 2628 – covering suitability to fumigate with phosphine – it must be subjected to a five minute, half-life pressure test when newly installed and a three minute half-life pressure test if already established.
If it meets the pressure test requirements, it will hold phosphine gas and other fumigants at a concentration high enough and for long enough to kill insects at all life stages (eggs, larvae and pupae).
The stored grain website includes several video demonstrations including a silo pressure test and the GRDC Pressure testing sealable silos Fact Sheet.
Reducing reliance on phosphine fumigations
Phosphine gas can only be used for grain that is stored in tested gas-tight silos and it is highly effective - but must be held at a lethal concentration for 7-10 days to kill insects at all growth stages.
There have been six documented detections of grain storage insects with strong phosphine resistance in WA (all of which have been eradicated), highlighting the need for correct fumigation and less reliance on this fumigant.
DAFWA says poor fumigation will result in only adults being killed and numbers building-up again from infestations from immature eggs and pupae.
It says in poorly maintained seed and storage silos, inadequate fumigation time promotes the selection of phosphine resistant individuals that survive and multiply.
Detecting phosphine resistant grain pests early will make eradication possible.
A free resistance test for grain pests is available from DAFWA - contact Nuccia Eyres or David Cousins from the Department’s stored grain insect group: 08 9368 3920.
GRDC's Grain Fumigation Guide Fact Sheet provides advice on application rates, handling advice, where and when to apply and tips on gas venting.
Storing high moisture and sprouted grain
Typical harvest temperatures of 25-30°C and grain moisture content of more than 13-14 per cent provide ideal conditions for mould and insect growth during storage.
The key to dealing with high moisture and sprouted grain is to act quickly and effectively.
GRDC’s Dealing with high moisture grain Fact Sheet outlines a range of management strategies, including:
- Daily monitoring of grain moisture and temperature for early detection of any mould or insects
- Blending high and low moisture grain evenly to achieve an average 12.5 per cent moisture and aerating
- Using aeration cooling for grain with moderate moisture (up to 15 per cent moisture content) for up to two months until drying equipment is available
- Using aeration drying in storage facilities at airflow rates of more than 15 litres per second per tonne
- Potentially using dedicated batch or continuous flow dryers for high moisture grain before storage.
Sprouted grain can be retained for seed, but it is best to use grain with a falling number of more than 150 and only retain this seed for one summer – as its ability to germinate will deteriorate faster than sound grain. There is also some evidence of reduced seedling vigour.
The South East Premium Wheat Growers Association (SEPWA) has produced booklets called ‘Dealing with a Difficult Harvest’ and ‘The WA Guide to High Moisture Harvest Management’ and these recommend minimal handling and using cool, aerated conditions when storing sprouted grain.
Aerating stored grain
A combination of good hygiene and well-managed aeration cooling during grain storage offers harvest flexibility, more marketing opportunities, better control of grain quality and potentially higher viability of seed grain for subsequent plantings.
Aeration of stored grain creates a low temperature in the silo to prevent mould, inhibit insect development, maintain seed viability and reduce grain moisture.
Insects rely on the environmental temperature for body warmth and will breed faster in warmer conditions.
If the temperature is below 20°C, they will produce less progeny in the storage period. But to stop reproduction, grain temperatures need to be below 14°C.
Through its Grain Storage Extension Project, GRDC has produced a Grains Industry Guide to Aerating Stored Grain that outlines cooling, drying and equilibrium tables and a Fact Sheet.
Economics of grain storage
Grain storage is a long term investment and its viability is unique to every grower.
A cost benefit analysis is useful to compare the expected returns from grain storage versus expected returns from other farm business investments.
A comparison of the cost of storing grain on farm versus paying a bulk handler to store it is also worthwhile.
Observations made by the GRDC Grain Storage Extension Project team indicate growers who are taking a planned approach to on-farm grain storage and are doing it well are being rewarded for it.
They say grain buyers are seeking out growers with well-designed storage systems that enable delivery of insect-free, quality grain without delay.
An example of this in WA is the Candeloro family, who store 85 per cent of grain (including wheat, canola and barley) produced annually on their 8000ha Toodyay property in state-of-the-art storage and handling facilities that have a capacity of 38,000 tonnes.
The aim is to capture premium prices by suppling quality grain direct to end users and their customers include Inghams Enterprises, Milne Feeds and West Coast Milling.
The Candeloros say another big advantage of an on-farm storage system is the opportunity to back-load trucks carting grain with fertiliser and lime, which spreads haulage costs across the grain enterprise.
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