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PCN ‘Issues’ Centre Stage at Potato Demo – The Scottish Farmer – Darryl Shailes

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THS-0956A new fenland potato site for leading agronomy firm, Hutchinsons, is already generating interesting results that will help shape future agronomy – including control of potato cyst nematodes (PCN).

An integrated approach to PCN management was one of the key topics which gained traction at Hutchinsons' recent open day hosted at AL Lee Farming Company's Folly Farm, near Ely, Cambridgeshire.

Parts of the site were under higher PCN pressure than last year's venue, the nearby Friesland Farm, which meant clear differences had emerged in varietal resistance and tolerance trials.

John Keer, of Richard Austin Agriculture, said that pre-planting assessments found an initial PCN count of up to 164 eggs/g soil, all globodera pallida species. “It's a slightly more mineral soil than the rich black Fenland at Friesland Farm, so doesn't offer as much resilience to the effects of PCN damage, which is helping highlight differences in our trials."

Some 18 varieties were planted on April 15 and each was being compared with and without a nematicide (fosthiazate). “PCN levels are consistently high across the trial area, which is bringing out differences in variety tolerance. We will take crops to harvest to see how yield is affected,” Mr Keer added.

“By measuring PCN populations pre-planting and after harvest, we will also be able to see how varietal resistance, or lack of, affects PCN multiplication in the soil.”

Initial observations reinforced the view that tolerant varieties were generally those with more vigorous growth that produced larger root systems better able to withstand feeding by larvae, he said. While tolerant varieties could withstand feeding damage and still yield well in the presence of PCN, without resistance, they would let cyst numbers multiply over the season.

“Tolerance and resistance are not linked. PCN still feeds on the roots of resistant varieties and those with low tolerance can, therefore, suffer quite a lot of damage, even if the crop's resistance prevents new cysts forming,” he pointed out.

At Folly Farm, varieties that had so far showed good PCN tolerance (i.e. little visible difference between treated and untreated plots) included Arsenal, Brooke, Cara, Performer, Rock, and Royal. In contrast, Maris Peer, Innovator, and Sagitta exhibited effects indicating lower tolerance.

"The really interesting detail will come when we measure the yield impact and see how g pallida varietal resistance affects final PCN count after harvest. The ideal would be to grow a variety with good PCN tolerance, and resistance to both species, that is also accepted by end users.

“That's not always possible, but the judicious use of resistant varieties and other integrated controls could buy flexibility to grow non-resistant varieties where necessary.”

THS-0990Also in the trials, a third year of the 'crop safety from post-emergence herbicides trial' again showed noticeable differences between varieties. Hutchinsons Root Crop Technical Manager Darryl Shailes said: “The impact on vigour and necrosis/chlorosis of four different post-em herbicides on seven varieties had been assessed, and results generally supported findings from previous seasons.

"There's always potential for some crop damage from post-emergence herbicides, but the extent is variety-specific. For example, bentazone had been consistently aggressive on Agria, causing noticeable scorch. Markies also suffered more scorch from bentazone than in previous seasons, potentially because the crop was under stress at the time of application,” he said.

“In contrast, Innovator was more tolerant of bentazone, but was susceptible to damage from metribuzin. Other varieties, such as Performer and Royal, showed minor effects and generally grew away well.

“We set up the trial to look at yield effects across the varieties to see if scorch or vigour reduction has a significant effect. Unfortunately, plots got waterlogged twice so establishment wasn't as we would have liked so it will be difficult to draw conclusions in terms of yield.

“However, this works gives us greater confidence to make recommendations to our clients, even where applications may not be supported by herbicide manufacturers,” Mr Shailes added. “Manufacturers do very little research on varietal impact and when they do it tends to be ultra-cautious.”

A desiccation and haulm management demo will be held this September by Hutchinsons, specifically examining desiccation options without diquat. Trials include different product timings and sequences, mechanical topping demonstrations and novel treatments. It will be held at Friesland Farm, Mildenhall.