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New Blight Strain Requires Fresh Approach to Control - Darryl Shailes - Farming Scotland Magazine

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Blight control strategies will have to change this season if potato growers are to combat the spread of a new aggressive, fungicide-insensitive/resistant strain of the disease, leading agronomy firm Hutchinsons says. 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, but Hutchinsons root crop technical manager Darryl Shailes believes the actual figure could be higher and all crops no matter where they are grown are potentially at risk. The new strain is at least, if not more, aggressive than the dominant blue 13 and pink 6, but the crucial difference is that it appears equally aggressive on foliar and tuber blight, he warns. "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." Furthermore, dark green 37 has reduced sensitivity to fluazinam, which is in many fungicides often used towards the end of the season to reduce tuber blight. "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.”