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Stubbornly wet soils and a high water table could increase the risk of wireworm damage in potato crops this season. Research over recent years... Wet soils increase potato pest threat

Stubbornly wet soils and a high water table could increase the risk of wireworm damage in potato crops this season.

Research over recent years has identified high soil moisture as a precursor for pest activity, with wet areas and flood plains increasing pressure levels, says Syngenta technical manager Andy Cunningham..

Cover crops

Reduced autumn cultivations and the ability of overwintered cover crops to harbour wireworm populations could see a double whammy of problems in spring-planted crops.

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

At the same time the wet winter and spring have severely curtailed opportunities to combat wireworm using integrated pest management techniques – making cultural control difficult.

Alternative approach

Alternatives include incorporating Nemathorin at the wireworm rate of 15kg/ha at planting. Syngenta trials in Lincolnshire last year showed this reduced wireworm damage to just 2% of tubers at harvest, compared to 9% in untreated areas.

Damage severity was also reduced. No tubers in the Nemathorin treated areas had more than five holes, and significantly fewer had one-to-five holes. Meanwhile, 2.5% of the untreated crop had three or more wireworm holes.

The application of Nemathorin at 30 kg/ha is permitted where PCN or free-living nematodes are being targeted. In a high-pressure field situation this halved the number of tubers seriously affected by wireworm, says Mr Cunningham.

“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.”

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

In terms of financial reward, Mr Cunningham says Nemathorin returned a margin of more than £2050/ha on a 40 t/ha crop, compared to less than £500/ha with Velum Prime.”

Variety selection

Soil analysis showed that Nemathorin treatment held the multiplication rate down to 2.5, compared to 9 in the untreated. In the Velum Prime treatments, the PCN continued to multiply at a rate of 7.5 times.

“IPM measures for all soil pests – including variety selection, rotation interval, adapting harvesting dates and target markets – can all help growers and agronomists mitigate against damage,” says Mr Cunningham.

“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.”