The mineral dust magnesite has clear potential for long-term protection of stockfeed oats if the grain is genuinely dry, but it is not effective against some major pests at higher grain moisture levels.
Magnesite (magnesium carbonate) is a relatively cheap natural product which has been used as a dust by some farmers around Young, NSW, to minimise infestation in farm-stored grain.
One drawback is that treated grain is more difficult to handle, and for this reason it is not accepted by bulk handlers or most grain traders. NSW Agriculture researchers, in a project supported by growers through the GRDC, found that magnesite would protect oats at moisture levels below 10 per cent for up to two years in farm silo trials.
At higher moisture levels it progressively failed to control grain borers and flour beetles but it did retain some control of sawtoothed grain beetle, which can be very common in stored oats.
The researchers recommended an application rate of 0.5 per cent as a compromise between effectiveness and difficulty of handling. They also found that magnesite may control insects better on feed wheat and triticale than on oats, but silo trials were too limited to make a firm recommendation.
At the 0.5 per cent usage rate, magnesite costs about $1.50 per tonne of treated grain compared with about $2.50 if Dryacide® dust were to be used at label rate. Magnesite however is less effective than Dryacide® in grain at 12 per cent moisture content. Because of the drawbacks to its use, magnesite is unlikely to be registered as a grain protectant without limitation. The researchers suggest that intending users seek advice on their specific situation from NSW Agriculture.
Contact: Dr Barry Wallbank
02 6938 1934