Peter Botta from PCB Consulting and Joanne Holloway from Industry and Investment NSW said growers needed to be extra vigilant in countering grain insects, to protect crucial international and domestic markets.

The warnings are particularly significant, given that more Australian growers are storing grains for much longer to add flexibility to their marketing program. The longer grain is stored, the more susceptible to insect infestation it becomes.

“Grain insect phosphine resistance is a very serious threat to the Australian grain industry,” Mr Botta said.

“Our markets demand Australian grain to be free of insects. It is crucial that Australian growers have strategies in place to store and deliver grain, control insects and limit the spread of phosphine resistance.”

Dr Holloway said random surveys across the growing regions of south-eastern Australia showed that live grain insects were found in 65 per cent of grain storages surveyed.

“Rhyzopertha, commonly known as the lesser grain borer, was the most common pest,” Dr Holloway said.

“Currently, even strong resistant forms of this insect can be controlled by the correct use of phosphine. But that may change with time.

“Of more concern are strong resistant populations of other pest species like flat grain beetle and rice weevil. These have been found at various sites in eastern Australia, and, unfortunately, are no longer controlled with the current rates of phosphine.

"In all insect species, it appears that the development of strong resistance to phosphine is due to its use in unsealed storages or at incorrect rates.

“As a consequence, it is absolutely vital that growers follow scrupulous hygiene, follow chemical label instructions and carefully manage on-farm storages.”