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What is Potato Blight?

Publication Date: 
1 April 2013

Potato and tomato blight is a disease caused by the fungus-like organism Phytophthora infestans which spreads rapidly in the foliage of potatoes and tomatoes causing collapse and decay. Read the 'What is Potato Blight?' Guidance for more information Download-What is Potato Blight?

Blight is more likely to occur during a ‘Smith period’, which is when the minimum temperature is 10ºC or above for two days, with a relative humidity of more than 90 per cent for at least 11 hours each day.  A 'near miss' can occur when conditions are not ideal for the spread of blight, but there can still be an infection risk for your crop. You can keep up-to-date on Smith periods by registering for a Fight against Blight account here register for FREE Blight Alerts. Once registered you can get Smith period information by visiting, where you can register postal districts and receive warnings by email and/or text.

Fight against Blight (FAB) and BlightWatch Account

Fight against Blight (FAB) Tools

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