Don't give blight an inch - BPC‏

Tight crop monitoring will be vital to keep blight at bay. That's the message to growers attending the British Potato Council's (BPC) blight seminar at British Potato 2007 (BP2007), following the worst blight season in recent years.

Almost 500 growers attended the seminars over the two-day event (November 28 and 29). Standing room only was available for latecomers to some of the seminars held on the BPC stand.

The first insight into the current state of changing blight populations was given to growers at the blight seminar. The new A2 mating types have increased their dominance to 80 per cent of samples surveyed. But genetic diversity has not increased, and mixed mating type outbreaks appear to have remained constant, at 21% of sites, reported SCRI's David Cooke. Two-thirds of 2006 samples were A2.

"We are now dealing with a different type of blight than we were three years ago. But all our research shows that current best practice is still the best way to deal with it," Dr Cooke advised.

Among the samples from 300 blight outbreaks monitored by SCRI and colleagues at Central Science Laboratory (CSL), there is no evidence of infections caused by oospores. Unlike asexual blight inoculum, that survives between seasons on green material such as volunteers or on tubers, oospores can survive in soil for several years and their spread is harder to check.

"There's no doubt it's been a tough year to keep blight at bay – weather and disease pressure combined to confound the best laid control plans. That will have implications for crops in 2008," warned Dr Cooke. "Expect to see high disease pressure early in the season."

But current best practice is the best control strategy, he stressed, despite the dominance of the new A2 blight genotype. "We've done tests and can confirm it is a slightly more aggressive, fitter genotype under test conditions. But if you stick to fungicide programmes that your buyers are happy with, you should maintain a robust defence."

Fungicide rates and spray intervals should be kept at advised levels. Vigilance will be the best way to keep blight in check, said Dr Cooke. "Use the BPC Fight Against Blight and Blightwatch service to assess risk. And above all, stay alert for signs of the disease and control sources of infection, such as outgrade piles and volunteers."

The work carried out by SCRI is part of a comprehensive blight campaign co-ordinated and funded by the BPC. This involves research and monitoring of blight populations and further work to assess control strategies. A vital part of ensuring growers have the latest information to keep the disease at bay are samples sent into SCRI and CSL for analysis by 350 blight scouts.

"These volunteers are ensuring we have up-to-date and reliable information on how Britain's blight populations are developing. The industry owes them a huge debt of gratitude," noted Dr Cooke.

The technical seminars at BP2007 were entitled Managing Change. Topics included action for stored crop quality and the latest on changing blight populations. Catchment-sensitive farming, new seed rate recommendations and reducing energy use in storage rounded up the seminar programme.