25 July 1997

Prepare for epidemic next year, warns ADAS

ADAS plant pathologist Bill Clark warns that yellow rust is bound to be a severe threat next season.

He is worried that wheat growers who achieved good control this season thanks to good management or a fluke may be complacent about keeping it out next season.

"Most growers who put on well timed sprays at the appropriate rate still ended up with infection in crops, as the gap between treatments at GS31 and GS39 was too long. Normally it would not have mattered, but it did this year. Growers who suffered control breakdown will have no illusions about the task they are facing next year." Mr Clark believes the original source was set-aside on many farms this year.

Growers must be prepared to face epidemic rust pressures in 1998, he says. "This is because it is not a one-off disease. It occurs when a single variety takes the lions share of the market, when conditions for two or three years favour the build-up and spread of a new race, and when set-aside pressures are high. All three conditions have now been met, so we can expect a lot of yellow rust next season."

Variety choice

Varieties for next season should be selected carefully. "But do not over-react. There are 15 or 16 which are potentially at risk from the new Brigadier race 9,17, but some will not be badly hit, as they have reasonable field resistance.

"Growers in high risk areas should use Baytan-treated seed, those elsewhere do not need to, but must check crops in November and December. Any infection seen then is an early warning of trouble ahead and fungicide must be sprayed in the early spring as soon as any new growth is seen.

CONTROL TACTICS

&#8226 Expect severe rust pressure.

&#8226 Volunteers in set-aside a risk – consider grass cover.

&#8226 Choose varieties with care.

&#8226 Use Baytan where risk high.

&#8226 Check crops Nov/Dec.

&#8226 Spray early next spring.

&#8226 Expect severe rust pressure.

&#8226 Volunteers in set-aside a risk – consider grass cover.

&#8226 Choose varieties with care.

&#8226 Use Baytan where risk high.

&#8226 Check crops Nov/Dec.

&#8226 Spray early next spring.