Control measures for potato cyst nematode (PCN) were highlighted during a demonstration day hosted by the Potato Partnership.
With a background pressure of 9 to 116 eggs of Globodera pallida per gramme of soil, it was a tough test for the potato varieties, nematicides and biological control solutions on trial at the partnership’s trials site in Suffolk.
To achieve a fair comparison, the field is separated into blocks according to the PCN pressure, and the treatments are stratified across low, medium and high classifications, explained Graham Tomalin, of VCS Potatoes.
“We’re trying to even out the pressure; it’s not perfect because it’s PCN,” he said
Tolerance and resistance
The trial aims to examine PCN tolerance and resistance between varieties. Leaf ground cover and yield are being compared against two control varieties: non-resistant, high-tolerance variety Cara; and non-resistant but low-tolerance variety Marfona.
Selecting the varieties to test was led by TPP members and seed houses – usually once varieties have been named and are close to market. However, some coded varieties in the trial are of interest to the group.
“We’re in the game of continuing to look at interesting things that might work,” said James Wrinch, of East Suffolk Produce. “It doesn’t mean it is the best, but you have to keep looking, otherwise you don’t learn.”
Mr Tomalin added: “It’s much better to know a variety that has a particular trait in a small plot than when you’re growing 20 or 30 hectares.”
Treatment options
The trials also looked at PCN treatment options. Maris Peer was used as the variety, which has a resistance score of two, and is known for poor tolerance, added to the high background pressure and stressful conditions for the crop this season.
“In this year’s trial, we have focused on the treatments that are currently available to us: Nemathorin (fosthiazate) and Velum Prime (fluopyram),” said Don Pendergrast, technical manager for non-combinable crops at Agrii.
“We have also looked at a completely new biological product, a potentially completely new synthetic product that might be available in the future, and investigated how we might partner with Velum Prime several products that have previously looked promising.”
Last year, the best-performing treatment, in terms of efficacy, was a programme of Velum Prime at full rate combined with Nemathorin at half rate and a silicone wetter. However, the full-rate Nemathorin has looked better this year.
“We have looked at Velum plus SP058, which is a silicone wetter,” said Mr Pendergast.
We have examined it in trials almost every year, consistently observing benefits in both canopy cover and overall yield. It works by improving the distribution of Velum in the soil profile, to get it to the PCN. The biologicals tested, notably the Nemguard liquid formulation, showed a benefit to the untreated, but were noticeably behind the synthetic options. The initial control looked in line with Velum Prime, then after six weeks, the performance dropped away.
“It is great that some biological options are coming through, but we really have to look again at utilising them slightly differently, either by stacking them with synthetic chemistry or finding ways to use them later in the season.”