Tackle late blight and Alternaria, growers warned

Growers are being warned to shake up their fungicide programmes to protect against a growing risk of Alternaria as well as late blight.

Alternaria, the trigger for early blight, has become a bigger problem because of the increasing popularity of susceptible potato varieties and changes in fungicide use.

Worst hit in the past two years was the Markies variety, while Saturna and Maris Piper had also been affected, said Bayer CropScience product manager Neil Thompson. Disease usually strikes from late July, but primary infection could be spotted earlier.

"Limitation of mancozeb use has contributed and there's been a knock-on effect from the development of more aggressive late blight strains," he said. "Recently introduced fungicides tackle them very effectively but have little or no Alternaria activity."

Initial symptoms could show two to four weeks from emergence. Tell-tale signs are irregular-shaped brown or black spots, developing into lesions with dark rings.

Agrovista technical manager Dr Mark Palmer advised growers to adapt fungicide programmes for susceptible varieties to protect early against this primary infection. "The key is to keep ahead of the Alternaria risk by using protectant products with dual activity against Alternaria and late blight," he said.

Palmer added that Consento was the most appropriate product to use during the rapid canopy-growth phase. "From canopy complete onwards, susceptible varieties still need to be protected against secondary Alternaria infection but the focus must be on late blight control," he explained.

"This is the time when programmes need to switch to the premier league late blight products - Infinito (fluopicolide + propamocarb), Ranman (cyazofamid) and Revus (mandipropamid) - to combat the more aggressive strains that are now dominating."


Have you registered with us yet?

Register now to enjoy more articles and free email bulletins

Sign up now
Already registered?
Sign in

Before commenting please read our rules for commenting on articles.

If you see a comment you find offensive, you can flag it as inappropriate. In the top right-hand corner of an individual comment, you will see 'flag as inappropriate'. Clicking this prompts us to review the comment. For further information see our rules for commenting on articles.

comments powered by Disqus

Read These Next

Can UK fresh produce come out of Brexit ahead?

Can UK fresh produce come out of Brexit ahead?

UK production horticulture can become more profitable under one possible Brexit scenario, while other more drastic scenarios will lead to only minor losses in profitability, in contrast to other farming sectors, according to a new report by levy body AHDB with Agra CEAS Consulting.

Business Planning - Staff are your greatest asset

Business Planning - Staff are your greatest asset

An effective strategy to retain staff is the best way for any business to avoid a potential recruitment crisis, Neville Stein advises.

How should agri-tech research for fresh produce function in a post-Brexit UK?

How should agri-tech research for fresh produce function in a post-Brexit UK?

One area affected by the uncertainty around Brexit will be the ongoing development of agricultural technology, seen by many as essential to retain Britain's productivity and competitiveness in fresh produce along with other farming sectors.