Cereal disease control risks are increasing

TAKE-ALL PROBLEMS are intensifying, septoria latent periods can shorten considerably and fungicide resistance is rife, all making cereal disease control more tricky for growers.

Such were the messages growers heard at a roadshow staged by Bayer in Peterborough last month.

“The take-all risk in second wheats has increased enormously in recent years,” said Geoff Bateman of Rothamsted Research. He blames the inclusion of more cereals in rotations, warmer winters, earlier drilling, problems with grassweeds and the move away from autumn nitrogen.

However, lower plant populations seem to cope better with infection and fungicides offering take-all suppression do help, he added.

Septoria was very difficult to manage last year, due to high temperatures following heavy rain, said ADAS”s Bill Clark. “The warm weather had the effect of shortening the latent period of the disease.”

Growers needed to spray within seven days of rain for control. But where chlorothalonil was used at T0 the timing pressure was eased. “The most common mistake every year is leaving too long a gap between T1 and T2.”

The gradual drift in the field performance of the triazole fungicides is continuing, he added, with the most consistent control from better triazoles used at high doses.

Over 20% of wheat planted last autumn is susceptible to the same strain of yellow rust, warned NIAB”s Rosemary Bayles. However, 2005 is unlikely to be a really bad year, thanks to inoculum levels being low from last season.