Potato blight pressure continues to increase following continued high humidity and rain showers, the British Potato Council (BPC) has warned.
The wet weather and poor travelling conditions will have increased spray intervals and this will challenge even the most robust spray programme, said SAC blight expert Ruairidh Bain.
"Where possible keep fungicide intervals short and use fungicides with some curative activity during the next application to shorten any extended intervals, through kick back activity."
What’s more, the weather has been favourable for tuber infection and spray programmes should include fungicides with good activity against zoospores and tuber infection.
"If blight is active on the haulm this will provide sufficient inoculum to infect tubers," said Dr Bain.
Late season protection reinforces the message that relying on the final two or three blight sprays to control tuber blight can be risky. Protection should be in place earlier in the season which is backed up by BPC-funded work that shows it is difficult to penetrate tall and dense crops with spray.
"Increasing water volume will help, but where growers are battling to get their spray programmes back on track after an extended interval, the main focus should be to get all under-protected crops treated as soon as possible," said Dr Bain.
He urges growers and advisers to keep checking the blight risk by using the BPC’s internet blight mapping programme at www.potato.org.uk.
Growers are also advised to maintain fungicide protection of the haulm until the crop is harvested or the haulm is completely desiccated.
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