A spray miss on the property of Stott Redman, at Hopetoun, on the south coast of Western Australia, proved to be a perfect trial for Exirel insecticide in the control of diamondback moth (DBM) and native budworm.
Mr Redman said most winters in the area are cold enough to keep DBM in check but 2024 was warm and dry, allowing the pest to build up.
Their local agronomist recommended an application of Exirel once DBM numbers reached a threshold on some of the canola, and the area was sprayed as the crop finished flowering.
There was also native budworm grubs and aphids at the time of spraying, with Exirel used as it had activity on both of those pests.
Stark display of insecticide effectiveness from spray miss
“I thought we were going to get through, but the numbers ramped up so quickly,” Mr Redman said.
Parts of the paddock had previously been sprayed with an aphicide and this information was included in the coverage map for the Exirel application. As a result, a small part of the paddock was missed, and proved to be an excellent trial to compare the Exirel treated and untreated crop.
The unsprayed part of the paddock was decimated with diamondback moth and native budworm damage and the area sprayed with Exirel was very clean.
“It was a couple of weeks after the application and I initially thought it was something in the boom – that the boys hadn’t cleaned it out properly,” Mr Redman said.
“When I went in to have a closer look it was major DBM and native budworm damage. The difference was almost to the nozzle.”
“I did a sweep in the Exirel part three weeks after spraying and couldn’t find anything.”
In comparison, the unsprayed section was covered with DBM and native budworm caterpillars.
Mr Redman said he’d rubbed out heads in the unsprayed section and the pods and seed were very small.
“They’ve been severely affected,” he said. “I’d expect half the yield.”
Agronomist Cameron Quenby, of South East Rural Traders, at Esperance, said they were conducting regular sweeps for DBM on the Redman property and saw populations explode from the start of August.
