Potato Review

44 POTATO REVIEW MAY/JUNE 2021 WEED CONTROL A CHIEVING good weed control without metribuzin can be difficult and will almost certainly be more expensive, but the competitive cost of new products and a broad spectrum of activity, have given growers and their advisers confidence that there is hope for the future. The concern facing growers extends beyond the regulatory uncertainty hanging over metribuzin. The worry is the lack of data on variety sensitivity [to metribuzin]. Data on the sensitivity of established varieties is available on the Adama website, but there are questions over that of the more recent introductions. Eric Anderson, senior agronomist at Scottish Agronomy said: “Metribuzin tolerance, or lack of, is often the first consideration when formulating a weed control programme. Without it, control is still achievable, but is often more complex and, potentially, costly, so care needs to be given to what products are used if unnecessary expense or false economies are to be avoided.” Growers are not averse to having to review weed control programmes with the loss of diquat ahead of the 2020 season forcing a A NEW HOPE Winning strategies for effective weed control in potato crops change in pre-emergence considerations. “Specifically, the issue was what contact herbicide to use at the pre-emergence stage? Diquat was preferred as a desiccant rather than as a herbicide, but its withdrawal meant programmes had to be reviewed because of the limitations on the alternatives, carfentrazone- ethyl or pyraflufen-ethyl,” Eric said. “Most growers opted for pyraflufen-ethyl in the form of either Gozai or Kabuki as their preferred desiccant with the other used as a pre-emergence contact as the application limits apply to the products separately not the active substance.” The change in tactics however, had implications for application timing. “On skirt or fenland soils where the variety is approved for metribuzin, then it’s a no-brainer. Metribuzin has the widest label covering annual-meadow grass and many broadleaved weeds. Adding Emerger will bolster control of chickweed and black-bindweed.” Chickweed Eric Anderson_Scottish Agronomy “Some growers were unprepared for the need to bring herbicide applications forward. The first spray needs to be made seven to 10 days after planting, typically once ridges are settled. Contact sprays,