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Old foe on the attack: British growers warned against new, aggressive fungicide-resistant late blight strain

Signs of blight on a potato plant.Potato growers in Britain are being warned to change their blight control strategies this season to combat the spread of an aggressive fungicide-resistant strain of the disease which has reached Suffolk. The dark green 37_A2 form of Phytopthora infestans has quickly spread across Europe, reaching England 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 agronomy firm Hutchinsons, believes the actual figure could be higher, with all crops – no matter where they are grown – potentially at risk. The new strain is at least, if not more, aggressive than the dominant blue 13 and pink 6 forms of blight, but the crucial difference is that it appears equally aggressive on foliar and tuber blight, he says. In addition, dark green 37 has reduced sensitivity to fluazinam, which features in many fungicides often used towards the end of the season to reduce tuber blight. More