Aphids spotted but no need to panic

01 Aug, 2015 02:00 AM
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Despite beet western yellows virus damaging canola crops across SA last year, farmers are being urged not to panic if they spot them in this year's crops.
Despite beet western yellows virus damaging canola crops across SA last year, farmers are being urged not to panic if they spot them in this year's crops.

DESPITE sightings of green peach aphids out in the paddock, growers are being advised to stay calm and step away from Transform.

SARDI Entomology research officer Bill Kimber said he had been out in paddocks the past fortnight and had seen the aphids, which was unusual but not alarming.

"Considering the cold and wet weather conditions, it has been unusual to see the aphids persisting," he said.

"Obviously the frosts we have had were not severe enough to knock the green peach aphids out, while the rain hasn't been heavy enough either to wash them off and onto the ground where they would die.

"So we have been finding them, but there is no need to panic."

Mr Kimber said that if they were transmitting the beet western yellows virus, it would be too late for farmers to minimise the damage.

"Once you see aphids in your crop, the virus would already be in the crop," he said.

"What people need to do is think about when they first saw the aphid in their crop and make an assessment.

"If it wasn't during that vulnerable, rosette stage, then damage will be minimal.

"And we were out in the paddocks at that first growth stage, and the aphids weren't there. We only started to see them a while after sowing, when crops were at the five-to-six-leaf stage, so they wouldn't have caused a lot of damage."

He advised growers to hold-off on spraying Transform insecticide, even if the aphids were present.

"The chemical company recommends using Transform only once a season, so now is possibly not the time," he said.

"Save it for later in the year, around spring, when the weather warms up and the aphids could possibly reappear.

"We don't need green peach aphids building up resistance to Transform, like it has with most of the other insecticides.

"Plus, if Transform is used, it kills off a lot of beneficial bugs – ones that prey on the aphid, and they will die before the aphid does."

Mr Kimber said it was concerning that the aphid was persisting through "this winter''.

"There is the possibility they are adapting to our conditions, but we have yet to research that," he said.

"It could also be that the weather has just been too mild as well."

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    Alisha Fogden

    Alisha Fogden

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