WIREWORM damage is now an increasing risk in potato crops across the country, including eastern counties and up into the Scottish borders, growers have been warned.
Speaking at this season’s Syngenta Potato Power meetings across the UK, Syngenta Potato Technical Manager Andy Cunningham said higher populations of the pest have been associated with increases in green cover throughout the rotation, increasing organic matter and soil moisture retention, reduced soil cultivations in min-till cereal establishment and less use of insecticidal seed treatments in arable crops. Maize, for forage or energy crop, is also a favoured host for wireworm.
Historically associated with grassland rotations in the south and west, changing farming practices and climatic conditions have resulted in a continuous creep of the soil-borne pest over recent seasons, according to Andy.
Damage from wireworm boring into tubers can result in high levels of crop downgrade, as well as creating an entry point for tuber rots and disease pathogens. Any historic evidence of infestation indicates presence of adult click beetle species in the area – and the ongoing threat of its larval stage, wireworm.
Challenging IPM strategies
Andy pointed out that all the risk factors for wireworm damage in potatoes are beneficial for the arable rotation, which makes for challenging IPM strategies through the rotation. He urged growers and agronomists should now be routinely risk assessing for click beetle and wireworm populations on fields in advance of potato cropping.
“Being aware of the problem is key for developing an effective control strategy to target treatments effectively and to minimise damage,” he said.
Monitoring techniques can use pheromone traps, with lures specifically for the three primary Agrostis (click beetle) species, or using bait traps of seed balls with 50:50 wheat and maize buried in the soil when conditions warm up, where wireworm are attracted to C02 produced as the seeds germinate.
“The pheromone traps are highly selective and give a very good indication of click beetle presence across the area, with capture thresholds as a guide to suggested actions. Bait traps are more specific to the field, but if you do find any wireworm then it accurately indicates potato crops will be likely subjected to attack.”
With the historic loss of Vydate and Mocap for wireworm control, Andy believes Nemathorin is now the only nematicide available for growers to reduce the damage caused.
“Trials have shown results can be very good, and equal to the nematicides previously used for the purpose. However, when wireworm is the only target soil pest the Nemathorin application rate is just 15 kg/ha – half the rate used for the control of PCN or for targeting FLN,” he said.
“The application technique is imperative to avoid mixing in too much soil and over diluting the treatment. It needs to be accurately applied and evenly incorporated into the top 15-20 cm of the soil profile only.
“For most growers that means applying as a specific pass on a bed tiller directly in front of the potato planter. Nemathorin is such an important and significant investment in the potato growing programme that it makes economic and agronomic sense to get the best performance with accurate application.”
