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“Ignore blight at your peril” says top researcher

Publication Date: 
26 July 2019

There was a hint of irony as Dr David Cooke addressed the audience in the soggy, humid conditions at the final Strategic Potato Farm Open Day at Bruce Farms, Blargowrie on 9 July

“Ignore blight at your peril,” was the clear message from Dr Cooke, a Research Leader for AHDB funded research into late blight at the James Hutton Institute in Dundee.

“This is perfect blight weather. After a hot start to the season, followed by a challenging July, we’ve seen 96 samples from 23 outbreaks, some of which have shown positive signs of the aggressive EU_36_A2 lineage” confirmed Dr Cooke.

 

 

In-season genotyping

The rapid evolution of aggressive blight strains has prompted a change in the response rate of pathogen monitoring. Scouts who register and submit samples using the FTA cards, which they received within their blight packs generally receive results within a week of submission.

Samples are collected by AHDB blight scouts, a network of growers and agronomists who use the cards to press fresh, sporulating lesions on to the card before drying and posting for research.

A recent change in weather has seen a flurry of samples submitted in June and July – compared to a slow start to the year after a dry April and May.

Dr Kathryn Hales, Knowledge Transfer Officer for AHDB Potatoes who leads the Fight Against Blight project said:

“Samples we received in June and July, which were confirmed as blight had genotypes assigned within four days.

“Results are then made available to the scout who submitted the sample, and then displayed by region via the mapping service on our Fight Against Blight website.

“We have recently refined that section of the website, which means that regional genotyping is more accessible for our blight scout network. 

“It’s likely to be a fast moving picture between now and the end of the season – so growers and agronomists should keep their eyes peeled.

“In order for us to keep up with the changing populations, our website is constantly changing to make blight management easier and scouts are reminded to use blight.ahdb.org.uk, rather than the old app.”

To date  there has been 64 lesion samples submitted from Essex, Kent, Norfolk and Suffolk that have tested positive for the 36_A2 strain. And the access to regional data (see below) such as this allows the industry to develop and adapt innovative, sustainable control strategies, including the use of alternative products on a more local scale.

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The Euroblight picture

This year’s Euroblight event, which took place in York in May started with a discussion of the status of late blight in Europe and beyond.

Dr Huub Schepers, a researcher who hails from Wageningen University in the Netherlands provided summaries from the 19 countries who have provided details to Euroblight over the last two years.

Dr Schepers explained that the most two most prevalent sources of primary inoculum from across the 19 counties was from seed and waste piles which stresses the importance of high quality seed and the managing of waste tubers and groundkeepers.

He concluded by explaining that the there was still work for tuber blight control and seed growers to do in order to combat the disease.

Dr David Cooke from James Hutton Institute discussed the changing genotype patterns of the P. infestans population in a global context. Information on new invasive clones:

Despite a low blight pressure season in 2018, we saw range expansion of the new clones that are displacing older genotypes across much of Europe. Combined, the older genotypes 6_A1, 13_A2 and 1_A1, decreased from 60% to 40% of the population from 2016 to 2018 whilst the newer genotypes 36_A2, 37_A2 and 41_A2 increased from 10 to 36% of the population from 2016 to 2018.

The spread of these clones reflects new challenges to late blight management, as they are clearly able to out-compete the existing types in the field. The additional diversity in the population across European crops as a whole increases the risk of blight management problems as new traits evolve such as virulence against novel host resistance genes and reduced sensitivity to fungicides.

Didier Andrivon from INRA in France also discussed the changing scene of blight genotypes. His results found the new invasive clones (36_A2 and 37_A2) are now expanding their ranges to the south (Belgium, France) and the west (UK), displacing other clones (13_A2 and 6_A1).

Results of fungicide sensitivity testing from the UK, NL and IPMBlight 2.0 all found no evidence of resistance to any active ingredients tested for 36_A2, but all found increased lesion sizes were produced across all products tested at the lower dose rates. All the results also confirmed 37_A2 resistance to fluazinam.

Dr. Andrivon’s work conducting pathogenicity testing of the new genotype found 36_A2 generates very large blight lesions and produces higher numbers of sporangia than other types. He concluded genotype 36_A2 is highly aggressive.

Using this information for IPM: Dr. Andrivon suggested the rapid adjustment of control tactics to population information, for example not using fluazinam where genotype 37_A2 is identified.

Some industry data presented by Audrey Derumier, Belchim Crop Protection reinforced the message that 36_A2 is a challenge to manage with its shorter latent period - faster lesion growth rate and higher sporulation capacity.  Belchim showed pictures of a pot trial where infected potato plants with genotype 13_A2 or 36_A2. Plants were sprayed at first signs of infection (i.e. testing curative activity). Visually the results were striking the disease caused by 36_A2 was significantly more difficult to manage than that caused by the 13_A2 genotype.

The AHDB Potatoes Fight Against Blight monitoring plays an important part of the European research and the 2019 in-season tracking is particularly valuable to the GB industry in planning their blight management. 

To date[JP1] , 173 blight samples have been processed from 43 outbreaks and almost 50% of them are of the 36_A2 lineage. This lineage is dominant in the eastern regions and has not yet been found in crops in the west or north of Britain.

The 6_A1 lineage comprises 30% of the samples and is found across the country whereas the fluazinam insensitive strain 37_A2 has been reported in six counties of England but not yet reported in Scotland or Wales in the 2019 season. Further details can be found on the Fight Against Blight website

Dr David Cooke will be presenting all of his findings, and a more at this year’s Potatoes in Practice. A full programme and details on the event can be found by going to our PiP event page.

Dr Cooke will also be at this year’s Agronomist Conference, further details will be provided as they become available.

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