Grains Research and Development

Date: 01.03.2000

Heliothis: cutting insecticide by 50% by Brendon Cant

Trapping grid provides data on thresholds for spraying to control heliothis.

A three-year, intensive research program in WA has developed precise economic thresholds for spraying to control heliothis (native budworm) in lupin, canola and pulse crops.

The outcome should give graingrowers the confidence not to spray infestations that will not cause economic damage.

According to AGWEST Geraldton-based entomologist, Kevin Walden, the new thresholds must be implemented interactively — in other words, calculations must be performed by growers as they survey their crops.

"When implemented in conjunction with the forecasting system based on pheromone trapping, I estimate the average area of crop currently sprayed with insecticide in WA will halve," Mr Walden said.

A hand-held computer is now being developed for this purpose.

"The new decision-making system will be accurate and easy to use and the first version will be tested this season," Mr Walden said.

The project has tested the precision with which a grid of pheromone traps can determine peaks in moth activity in the cropping regions of south-west WA. Pheromone traps, which are inexpensive and easily maintained, attract male native budworm moths by using a perfume usually emitted by female moths.

Growers will be able to maintain the trapping grid and information on moth numbers can be collated by AGWEST and communicated to growers and support industries via the PESTFAX system developed by Mr Walden and AGWEST.

The trapping grid Mr Walden has established from Kununurra to Albany could be the key to saving the WA grains industry millions of dollars in crop damage from an invasion of the potentially devastating pest.

Supported by growers and the Federal Government through the GRDC, Mr Walden has been able to show that spring outbreaks of heliothis in south-west WA originate from moths migrating out of the arid interior.

The size and duration of moth migrations depend on the budworm successfully completing a winter generation in that region which is, in turn, reliant on the extent of autumn rainfall.

Therefore, thanks to eight years of daily, or at least twice-weekly, checks of traps along that grid by Mr Walden and a dedicated team of volunteers, predictions can now be made of the extent and timing of migrations.

Program 2.7.1 Contact: Mr Kevin Waiden 08 9956 8555