Canola aphid fears grow

A statewide map of testing results has shown that populations of the pest, which hosts the destructive beet western yellow virus, are 100 per cent resistant to three major chemical groups.

Carr's Seeds agronomist Denis Pedler, Cummins, says he is alarmed by the results.

"I received them from a number of samples of GPA found in canola crops that I had tested for insecticide resistance, from Yeelanna and Kapinnie," he said.

"They both showed 100pc resistance to synthetic pyrethroids (Alpha Scud), organophosphates (Chlorpyrifos, Dimethoate) and carbamates (Aphidex)."

The map that came with the testing results showed that all tested populations statewide were resistant to the above groups of chemicals.

"The levels of resistance may vary between populations but it shows that Transform insecticide will be the only effective chemical in controlling GPA," he said.

Mr Pedler said while the Lower EP was lucky to get away with only minor damage this season, the concerning issue is what would happen in 2015-16, particularly if GPA developed resistance to Transform.

A bigger issue was that affected canola had been sown with seed treatments Gaucho or Cruiser Opti, which came from the same chemistry group as Transform.

"We've been growing canola in this area for about 30 years and using all the products that GPA has resistance to for the best part of (that time), so they've been developing resistance," Mr Pedler said.

"The big question now is how long until GPA develops resistance to Transform and, if that happens, what do we do?”

He said canola was an extremely important crop to growers on the Lower EP, accounting for between 40pc and 50pc of the cropping rotation in this area.

SARDI principal research scientist Jenny Davidson said GPA could develop resistance to Transform if it was overused.

She recommended growers try a test strip of organophosphates, especially dimethoate, to see if it was still active.

* Full report in Stock Journal, August 28, 2014 issue.