27 October 1995

Rhyncho:Looking for new cocktails

FUNGICIDE mixtures should be used to maintain the effectiveness of triazoles against rhynchosporium.

"Nothing is coming along that is as effective as triazoles at controlling the disease," IACR-Long Ashtons Sheila Kendall told the ARIA meeting at Long Ashton.

But the disease has shown varying shifts in sensitivity to some triazoles in recent years, leading to the development of highly resistant strains in some cases, Dr Kendall said. Fortunately, others remain unaffected as yet, she added.

But for how long remains unclear. "Although new generation triazoles give very good control, it is not a good idea to use them on their own. Genes for resistance are very readily selected."

There is a "clear need" to protect such fungicides by using mixtures, Dr Kendall said. But MBCs need to be used with care. Resistant rhynchosporium strains have been isolated in western areas, though the east seems less affected.

New fungicide groups will soon be available and will provide a useful alternative partner. And morpholines work well when used with triazoles, she added.