SACs rhyncho warning

8 December 2000

SACs rhyncho warning

RHYNCHOSPORIUM poses one of the most severe threats to barley and the problem is getting worse, according to Simon Oxley, senior cereal pathologist with SAC.

Dr Oxley presented initial findings from the first year of research into the disease to the Perth roadshow audience. When fungicides were investigated no single product achieved effective control, he said. Triazoles were also proving less effective than they were 2-3 years ago, suggesting resistance is becoming a problem.

Mixtures of fungicide gave better control, he said. Unix (cyprodinil) was a good stem base fungicide and the best control came from a mixture of that at 0.5kg/ha (half dose) and Twist (trifloxystrobin) or Corbel (fenpropimorph) at full rate.

"That regime would, however, be pretty poor on yellow rust, so watch that you are not controlling one problem only to end up with another," Dr Oxley warned.

Timing was also critical. "You have got to get in early or you will never get on top of the disease," he said, adding that fungicide treatment at growth stages 25 and 31 seemed to produce the best results.

The project is also pointing to variations in varietal resistance, depending on disease pressure and crop growth stage, Pastoral looking like a 4 for resistance, not a 7 or 8.

Comments on such variations could be added to the recommended list, he said. &#42

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