Keeping insects out of stored grain will become easier with the expected registration soon of a biologically derived protectant.

Queensland Department of Primary Industries and Fisheries (DPI&F) principal entomologist Greg Daglish said three years of laboratory trials had shown the protectant, called spinosad, was effective in controlling all genotypes of a major stored grain pest, lesser grain borer, which is becoming increasingly resistant to registered protectants.

Dr Daglish said a major chemical company had asked the Australian Pesticides and Veterinary Medicines Authority to register a product containing spinosad, and expected approval in time for the protectant’s use on this season’s winter grains.

He said the registration application was a result of Grains Research and Development Corporation-supported testing in the DPI&F’s food protection laboratory and by other specialists in the New South Wales Department of Primary Industries.

The research centred on determining which species could be controlled by spinosad,  application rates, efficacy against resistant and non-resistant strains of nine species, and the pesticide’s longevity, he said.

Dr Daglish said he is also involved now in a large scale trial of spinosad on wheat stored in a grain handler’s silo in Victoria.

He said spinosad’s registration would be timely because increasing insect resistance in the lesser grain borer meant the industry faced challenges with current protectants.

“Only about 20 per cent of the grain crop is now treated with a protectant, but this could change with the availability of a more effective product to support phosphine, the widey used grain fumigant,” Dr Daglish said.

“The advantages of spinosad over the registered protectants are its efficacy against resistant strains of the lesser borer with nine months longevity, its safety, and likely wide market acceptance through its use in other countries, including the United States.

“Another advantage is that it’s very safe to use and has low impact on human health,” Dr Daglish said.

He said a mixture of spinosyns, naturally produced toxins of a soil bacterium, was the basis of the protectant.

“There’s every chance insects will eventually develop resistance to spinosad. When and where will depend on how well its use is managed. 

“Users will need a management plan that relies on the rotation of control measures,” Dr Daglish said.

He said DPI&F senior research scientist Dr Manoj Nayak had been closely involved in the spinosad research.

Dr Daglish said the DPI&F food protection group also had an ongoing research and extension program to ensure that phosphine continued to provide immediate control of stored grain insect pests.

He said the group’s work included information and extension activities on insect pest management and the appropriate use of the fumigant, and mapping insect resistance hot spots in Queensland and NSW to find causes and solutions.

“We need to prolong the useful life of phosphine to help meet market requirements of insect-free grain, which is in the best interests of the grain industry, including growers, merchants and handlers,” he said.

More information on stored grain insect pest management is available from the DPI&F website or by telephoning the DPI&F (13 25 23).