Weather raises blight pressure

Growers will be praying for better weather to allow them to continue with their blight spray programmes this season.

Blight products with curative activity are essential as potato growers try to tackle extremely high blight pressure, agronomists say.

Difficult spraying conditions, both overhead and underfoot, are increasing the risk from the disease, which has had perfect conditions in the past few weeks for its development.

About 30 cases of blight had been reported on the British Potato Council’s Fight against Blight website for the week between 18 and 25 June.

Window on the web

Potato growers can access detailed European comparisons of blight active ingredient activity at the EuroBlight website

Clicking on the fungicide comparison link in the results section on the right-hand side of home page takes growers to a table comparing the activities of all the blight actives available in Europe.

Updates of where blight has been found in the UK and to sign up for text message updates can be found on the British Potato Council’s Fight against Blight website

“It is the highest pressure I’ve known for years,” Malcolm Smith, technical support manager for Masstock, said on Tuesday [26 June]. “And it is being combined with an inability to get sprays on [because of inclement weather and not being able to travel on fields].”

That was causing intervals to be stretched, he said. “It is a bit worrying because it is so early. We’ve only just got to stable canopy.”

When growers could travel again he recommended applying chemistry with the best curative activity (see window on web panel). “That’s products including cymoxanil or Valbon. Merlin and Tattoo also have a degree of kickback.”

A Belgian trial suggested Valbon (benthiavalicarb-isopropyl + mancozeb) had the strongest kickback, he noted. “It was only one trial, but based on that work we are using it in programmes now.”

Alternative options included using a protectant blight fungicide, such as Ranman (cyazofamid), Revus (mandipropamid) or Roxam (mancozeb + zoxamide), but only in mix with full rate cymox­anil, he said.

Blight concern

  • High infection pressure
  • Lack of spraying opportunities
  • Blight in some crops
  • Need for curative activity
  • Spray as soon as possible






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