20 June 1997

Fungicide residues to be measured

DETECTING the amount of fungicide remaining in plants will allow better targeting of subsequent sprays. That will ease management, save money and benefit the environment, says the SACs Simon Oxley.

He is leading a Home-Grown Cereals Authority-funded project to develop a diagnostic test to do just that. A specific antibody for tebuconazole has already been developed at the CSL.

"We hope to produce others, including some for new chemistry, so we could eventually have a cocktail to identify different chemicals, and their concentration."

The project is examining levels at which fungicidal efficacy falters. Once that is known, antibodies could be used to identify spray rates and timings.

There are several potentially valuable uses, Dr Oxley explains. If it rained soon after spraying, growers could test the crop to see if they needed to retreat. They could also assess the amount left in the plant at second or subsequent spray timings, and adjust dose or timing accordingly.

The technique could also be used with new systemic triazole seed treatments, he adds. "Fungicide levels could be assessed from early spring onwards to find out when to spray." The test could also identify differences in uptake in a dry or wet spring, and how evenly the product is taken up by tillers.

The eventual aim is a hand-held in field tester, although that is several years away, says Dr Oxley.