Seeking new ways to protect potatoes

Diquat and pencycuron are among the key actives the potato sector has had to wave goodbye to in the last year and now the future of mancozeb also hangs in the balance.

Following an EU decision against reapproval last autumn, the fungicide has gained a temporary reprieve here as a result of post-Brexit legislation, which rules that active substances due to expire in the EU within three years of December 31, 2020, will be granted a three-year extension under the new GB regime.

Mancozebs multisite activity has been essential in ensuring growers are able to implement a robust spray programme containing alternating modes of action and without it building a cost-effective disease control programme is going to be a problem many growers face going forward, believes seed potato grower Tom Cargill, who farms in north east Scotland.

Mr Cargills farm, which sits between Aberdeen and Dundee, exports around 70% of its seed potatoes to countries outside the EU, including Iraq, Egypt and Thailand.

And while alternaria, which is controlled by mancozeb, is not much of a problem in Scotland, some varieties suited to export are susceptible, he told the BCPC Disease Review.

We grow Atlantic, which is susceptible we had a wet autumn like a lot of people and they do make a bit of a mess, but a couple of days after all the pig huts and fences have gone we can level it off, subsoil and get a bit of structure back and create a decent crop after it. As well as clearing up groundkeepers, there are also fertility benefits, Mr Pratt added, with soil P and K levels typically increasing by an index of 1 after pigs.

Were getting paid to put nutrients back in the soil, but site selection is very important.

Youve got to have nice light, level and sheltered land. There are some issues with pigs, he added, including erosion and fertility hotspots.

We also have to be careful what we follow in the next crop.

We usually follow with maize and sugar beet because theyre good scavengers of fertility and we spent quite a lot of time levelling hotspots off where the huts had been.

Weve got to a position where we dont see those hotspots now, said Mr Pratt.

Yorkshire veg grower M.H. Poskitt has teamed up with sustainable crop protection product developers Eden Research to create and trial the new biofungicide product designed to protect and improve the quality of root vegetables.

It is hoped the project could eventually provide farmers with a naturally-based, chemical-free product to protect against late blight in potatoes.

Sean Smith, chief executive officer at Eden Research, says: Its actually not that unique a situation.

Poskitts farm manager James Bramley had been walking field boundaries and happened to notice in an area a fairly common weed was present, crops looked more vigorous and generally healthier with lower incidence of disease.

He noticed this across a couple of crop groups including potatoes, carrots and parsnips. Poskitts growers and agronomists then undertook their own experiments, turning the weed, common mugwort, into tea and applying it to plants, where the impact was quite clear, Mr Smith adds.

Conclusive

On late blight they saw some pretty conclusive results, much stronger than what they would have anticipated, so they started speaking to regulatory consultants to find out about product development. Over the next two years, Poskitt and Eden Research will develop and commercialise the product.

We think its a class of compounds broadly referred to Biological solution to late blight on the horizon as terpenes that is having such good activity against late blight.

We are now working to create a product that is efficient and gives consistent results. And while some might consider bioproducts a compromise in comparison with chemical controls, Mr Smith says they have the potential to replace less sustainable inputs, with some products already showing better efficacy than their chemical comparators.

We have always had this view that we need to go out there with efficacy that is comparable to conventional chemistry.

IPM is the future and the way we see Eden fitting into this is replacing the chemical component of an IPM programme where possible.

For example, when we are looking to prevent or cure botrytis on grapes, we have products that perform at least as well as active ingredients so were going head-to-head with chemical products.