New weapons, old war

Adelle Dunn checking sweet corn
Yanco technical officer, Adelle Dunn, checking the sweet corn trials for pest and beneficial insects at the seedling stage and (inset) in the laboratory with insects she collected.

Efficacy trials have revealed two promising insecticides that fit Integrated Pest Management (IPM) protocols for sweet corn growers in the perpetual war on invading insect pests, particularly heliothis.

Both are narrow spectrum insecticides in the experimental stage, being developed by different chemical companies.

“They gave excellent control of heliothis, the major insect pest of sweet corn,” NSW Department of Primary Industries (DPI) district horticulturist, Tony Napier, said.

“The level of control was as good as any other insecticide currently registered for use.”

NSW DPI has evaluated the insecticides with the sweet corn industry and chemical companies.

Left uncontrolled, heliothis can decimate a crop, doing the most damage about two months in, when cobs are beginning to form.

“The presence of beneficial insects in sufficient quantities will control heliothis without any insecticide,” Mr Napier said.

“If beneficials are present, but in numbers too low for adequate control, growers will require a narrow spectrum insecticide.”

A technical officer at Yanco specialising in IPM systems for vegetables, Adelle Dunn, has been evaluating the new generation insecticides for their effect on all the insects found in sweet corn.

“We had a good range of beneficial insects in our trials this year and it was pleasing to see the two new insecticides had little effect on them,” Ms Dunn said.

“Ladybird beetles, pollen beetles and pirate bugs were all present in high numbers in the trial and the new insecticides had little effect on them.

“It is important to try to preserve these insects in the crop, as they will clean up any heliothis invading after the insecticide applications.”

Mr Napier said the research results from these trials will help chemical companies register the new narrow spectrum insecticides.

“If we want to continue winning the war against heliothis, it is important to continue developing new insecticides for all crops, not only sweet corn,” he said.

“A greater range of choice will help avoid heliothis developing insecticide resistance.”

According to Mr Napier, narrow spectrum insecticides are a lot softer on non-target insects than the older generation broad spectrum insecticides.

Where broad spectrum insecticides kill almost all insects present in a crop, narrow spectrum insecticides only kill the target pest and have minimal effect on the other insects.