Growers are being warned that wet soils over the winter and spring could increase the risk of wireworm damage in potato crops this season.

Research has identified high soil moisture as a precursor for pest activity, with wet areas and flood plains increasing pressure levels.

This, coupled with other risk factors of reduced cultivations in the autumn and the capability for overwinter cover crops to harbour wireworm populations, there’s a double whammy of potential problems in crops planted this spring, warns Syngenta technical manager, Andy Cunningham.

“Wireworm is an increasing issue in cereal rotations, particularly where there’s grassweeds in stubble or left as cover – be that with stewardship scheme compliance or limited chance for cultivations in the autumn that disrupt the pest.

“Weather conditions have also severely curtailed growers’ opportunities for integrated pest management (IPM) cultural controls of wireworm,” he explains.

Trial results

Results of Syngenta trials in Lincolnshire last year showed Nemathorin (fosthiazate) incorporated at the wireworm rate of 15kg/ha at the time of planting reduced the proportion of wireworm damaged tubers to 2% of the harvest, compared with 9% in untreated areas.

Furthermore, the severity of damage was also reduced with no tubers in the Nemathorin-treated areas showing more than five holes, and significantly fewer with 1-5 holes. More than 2.5% of the untreated crop had an unacceptable three or more wireworm holes.

Andy says trials show using Nemathorin at a higher rate of 30kg/ha in a high-pressure field situation can halve the number of tubers seriously affected by wireworm. This application rate is permitted where PCN or free-living nematodes are being targeted.

“PCN remains the most serious soil pest of potatoes – hitting yields in the current crop and, if left unchecked to multiply, the future viability of fields for potato growing in the rotation,” he adds.

In an average of eight recent trials where PCN was present, Nemathorin delivered an average yield increase of more than 17t/ha over untreated. In the same trials, fluopyram achieved 4.5 t/ha extra yield.

Return on investment

In terms of financial reward, Andy calculates on a 40t/ha crop, Nemathorin returned more than £2050 per ha margin over input cost. “Furthermore, when the soils in all the trials were analysed, the Nemathorin treatment held the multiplication rate down to 2.5, compared with 9 in the untreated.

“IPM measures for all soil pests, including variety selection, rotation interval, adapting harvesting dates and target markets can all help growers and agronomists  to mitigate against damage. But where there is a risk of losses, the use of Nemathorin could provide additional protection to yield and assure the sustainable long-term viability of potato production,” he concludes.