Growers warned to beware of new potato blight strain

Growers will need to change their strategies to cope with a new potato blight strain now discovered in Suffolk and other parts of the UK, an expert has warned.

The dark green 37_A2 form of phytopthora infestans has spread quickly across Europe, with the aggressive, fungicide-insensitive/ resistant strain arriving in the UK two years ago when five cases were reported.

Around 20 cases were officially recorded in 2017, mainly in the West Midlands, Yorkshire and Kent, and more recently in Suffolk.

However, Darryl Shailes, root crop technical manager at crop production specialists Hutchinsons, believes the actual figure could be higher and all crops no matter where they are grown are potentially at risk. He warned that it was proving difficult to contain using conventional fungicide treatments.

“There was a massive failure of fluazinam at the Eurofins blight trials last year and dark green 37 was implicated in several cases of store breakdown,” he said.

“Fluazinam has been a cost-effective option for tuber and foliar blight, especially against the blue 13 strain, but until we have access to real-time information to determine the exact genotype of blight spores present in the field, we have to question its position in blight programs.

“The yield loss from foliar infection of blight is often very small except in the worst years but the consequential losses from tuber blight can be massive.”

John Keer of Richard Austin Agriculture said dark green 37 is most likely to have reached the UK in imported seed, but also spreads via airborne spores. “We expect a progression of the new strain from hotspot areas this year, but it’s hard to predict where we’ll see it. Blue 13 and pink 6 took two or three years to spread and become more dominant, whereas other genotypes such as A33 have remained very localised,” he said.

All growers should be wary of the new strain and not assume crops are ‘safe’, he said.

A ‘myriad’ of alternative chemistry could be used, he said.