Corteva Agriscience says growers need to keep a close eye on weed control
Potato growers are facing a different proposition when it comes to weed control this spring compared to 2022 following delayed planting of much of the UK’s maincrop, according to Corteva Agriscience.
A wet March saw planters unable to travel and seed stocks stuck in sheds while almost 120mm of rain fell, representing 80 per cent more rainfall than is typical for the month, according to Met Office data.
South West and South East England were the worst-affected regions, while growers in the North West and North East were spared some of the rain but battled more frosts and snow.
While planting is now well underway, Corteva said maincrop potatoes are likely to have been drilled later than planned and, where April showers have continued, residual herbicide programmes may not have been applied in a timely manner, if at all.
The bulk of the weed control workload in potatoes is carried out using residual chemistry applied to ridges shortly after planting. Weeds evading the scope of residuals are tackled with a post-emergence spray, typically in May.
Craig Chisholm, Corteva’s field technical manager for potatoes, said: “There are three main reasons why weed control is important in potatoes. The first is protecting the crop from yield-robbing competitive weeds, and the second is ensuring harvest machinery is not hampered or slowed down.
“But perhaps the most important reason to keep weeds in check is to reduce the risk of blight through sheltering leaves or contributing to a more favourable microclimate.”
Chisholm advised growers who are unable to get their pre-emergence herbicides on to instead use a post-emergence approach as the crop encounters warming, moist conditions.
Titus is a sulfonylurea herbicide containing rimsulfuron for control of broad-leaved weeds in potatoes. Applied in mixture with metribuzin, it provides the most comprehensive post-emergence weed spectrum, Corteva said.
“Titus is most effective against small, actively-growing weeds, and should be applied before the crop provides a sheltering canopy, which may compromise activity,” Chisholm added. “Titus is safe across all varieties, but should not be applied to seed crops, and users should check that their variety is listed as tolerant of metribuzin before including in the mix.”
The selective herbicide has been a mainstay for potato growers for almost three decades, with a weed spectrum that includes cleavers, chickweed, redshank, mayweed and oilseed rape volunteers. Titus has also demonstrated excellent activity on some grasses, notably couch, Corteva pointed out.
Chisholm said: “The qualities of Titus are well known to potato growers and agronomists in an environment where there are relatively few tools to do an important spring job.”