Once every two years, anyone with a serious interest in the potato industry heads to the Yorkshire Event Centre for a specialist trade show. CPM attended BP2023 in Harrogate for insight into the latest sector developments, including what’s happening with EU_43_A1.

“The introduction of new, non-clashing chemistry is essential.”

By Janine Adamson

Attendance at industry trade shows can often be up and down, depending on whether field operations have to take priority and how pressured the day-job is. But with the continued threat of a Danish blight strain, BP2023 in Harrogate proved a lively platform for discussion.

Experts first highlighted the problem of EU_43_A1 in January 2023, with stewardship advice promptly issued from Syngenta due to the strain’s resistance to the carboxylic acid amide (CAA) group of fungicides, including mandipropamid (found in Revus).

The advice included always mixing CAA fungicides with a partner product, alternating sprays with different modes of action, and to limit the number of CAA fungicides within the blight programme (as recommended by FRAC guidelines).

Then in June it was announced that the Fight Against Blight (FAB) service which monitors genotypes and shifts in fungicide sensitivity was to continue after securing industry sponsorship.

FAB project leader Dr David Cooke from the James Hutton Institute presented this year’s results live at BP2023. He says there have been no significant population changes in GB during 2023, with 36_A2 (51%) and 6_A1 (34%) still dominating the 830 genotypes isolated from 1,500 samples sent to FAB. As for EU_43_A1, according to the screening, it remains elusive.

Furthermore, sensitivity testing of the main GB genotypes against key fungicide actives (ametoctradin, amisulbrom, oxathiapiprolin, propamocarb and zoxamide) found no efficacy concerns this year.

However, Corteva recently confirmed EU_43_A1 resistance to oxathiapiprolin (OXTP) in some parts of northern continental Europe – as found in products such as Zorvec Enicade. And confirmation of a single finding of the strain in a sample taken at Teagasc’s research station at Carlow, Ireland, further fuels concern, says the firm.

Harper Adams University’s Dr Matthew Back says although the EU_43_A1 genotype hasn’t been recorded in the UK, there’s always risk from incursions via airborne sporangia. “These can travel distances over 40km and have been detected at 1km from the ground.

“If detected, it’s important that the principles of integrated disease management are applied – paying attention to sources of P. infestans such as dumps/cull piles and groundkeepers. It sounds simple, but these sources aren’t always under the best management,” explains Matthew.

James Cheesman, technical manager at Certis Belchim (sponsors of FAB), says that similar to advice from earlier in the year, growers must use all modes of action available when constructing balanced programmes. He stresses that fungicide groups should be mixed and alternated as much as possible, and incorporating multisite inhibitor mancozeb will also be important.

So on reflection, it could be argued that BASF launching a new late blight fungicide at BP2023 was timed to perfection.

Matthew Goodson, BASF specialities market manager, says the two active ingredients found in Privest (ametoctradin+ potassium phosphonates) offer a synergistic effect when it comes to controlling the disease. “The aim is to build resistance early in the programme by working with the plant,” he explains.

Ametoctradin is classified under the QoSI chemistry group, which Matthew Goodson says sets it apart from all other actives including traditional CAA and QiI chemistry options, meaning Privest is in a ‘league of its own’. This is combined with potassium phosphonates to boost the plant’s natural defenses.

“Privest introduces much-required variety to blight control programmes which is essential both for mitigating the risk of resistance development and efficacy,” adds Matthew Goodson. “We believe it gives the best start to a blight programme by going in early and strong, freeing up the ability to use other products later in the season.”

Specialities business development manager, Paul Goddard, agrees that EU_43_A1 and the associated limitations to CAA chemistry serve as a stark reminder of how swiftly disease evolution can impact crop protection. “That’s why the introduction of new non-clashing chemistry, like Privest, is so essential.”

Also under the spotlight was liquid tuber treatment, Honesty (fluxapyroxad). The SDHI fungicide targets a range of diseases including rhizoctonia, silver scurf and black dot, as well as having incidental activity against dry rot and gangrene.

A rather eye-catching shade of bright blue, Honesty is approved for use on all potato crops whether that’s seed for seed, for ware or for processing. BASF’s Luke Pollard says the blue hue gives growers reassurance of consistent coverage, but the real magic is in the product itself.

“We’re really excited about Honesty because not only does it give comprehensive disease control, it also brings physiological benefits to the crop giving more even stolon initiation which results in more marketable grade out.”

For something completely different, BP2023 attendees had the opportunity to learn about Nucrop – a hybrid herbicide concept that combines a conductive liquid called Volt.fuel with electro-physical weeding. The all-in-one-pass solution is being developed by Nufarm and German ag-tech start-up, Crop.Zone.

In terms of potatoes, it’s hoped Nucrop could be the answer to the ongoing desiccation conundrum following the revocation of diquat in 2019, providing an alternative to chemical control or flailing.

Nufarm’s marketing manager Louise Dalgliesh says the concept works by pre-treating plants with the conductive liquid and then applying an electrical charge to desiccate. As a result, the operation is achieved with a high degree of efficiency but lower energy consumption than conventional weeding technologies.

And compared with conventional desiccation techniques, one Nucrop application is equivalent to two chemical passes, explains Louise. Nucrop is initially focussing on potato desiccation, but the plan is to expand applications to include wider weed control.

Over in the seminar hall, topics included the latest agri-tech case studies, tackling storage challenges, and British potato market trends. Echoing the message from the main exhibition hall, ADAS’s Dr Faye Ritchie presented the findings of a three-year project led by a consortium of industry players including ADAS.

The field experiment aimed to provide evidence to determine and rank the effectiveness of fungicide resistance management strategies, which include blocking, alternation, and with and without a solo/multisite fungicide. The trial was based around the presence of EU_37_A2 and fluazinam use.

Summarising the results, Faye says the trial showed repeated and sequential application of a single site mode of action increases selection for fungicide insensitivity. Equally, mixture partners and alternation are two of the most effective resistance management tools for late blight.

However, Faye stresses the role of non-chemical control methods such as choosing cultivars with resistance, improving out-grade pile management and effectively controlling volunteers. She believes these can often be over-looked yet remain valuable.

This article was taken from the latest issue of CPM. Read the article in full here.

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