Potato Review

34 POTATO REVIEW MARCH/APRIL 2022 WEED CONTROL H IGHER fertiliser costs, price pressure from discount supermarkets, the potential loss of more key actives in the crop, plus issues around maximum residue levels (MRLs) all point towards another very challenging year for UK potato growers, according to agronomist Fiona Law-Eadie. Dividing her time between Produce Solutions, a division of Greenvale AP, and sister company Crop4sight – a potato-based software management company, Fiona annually advises growers across Shropshire, Herefordshire and Oxfordshire and, with 35 years of experience in potatoes, she predicts that 2022 could be one of the most challenging yet for the industry. “There’s no doubt farmers have suffered significant product losses in recent years. Effective weed control strategies have been hit hard with the loss of both linuron and diquat and, with other products now under the regulatory spotlight, it’s not going to get easier in the foreseeable future,” she said. “Within my territory challenges are linked to a large variation in soil types, including very light land unsuitable for metribuzin, a wide range of following crops and some metribuzin sensitive varieties, so early weed control planning is essential. “On early chitted crops I prefer to get residual herbicides on as early as possible once ridges have settled and there is good moisture in the soil. Praxim (metobromuron) is certainly a go-to residual for me in the tank mix. It’s flexible, extremely crop safe and, when applied at a rate of 2.5L/ha, it shows good activity on a broad spectrum of weeds including annual meadow grass, common groundsel and annual nettles. “In higher weed burden situations my tank mix preferences are either Praxim + aclonifen or prosulfocarb when dealing with metribuzin sensitive varieties, or Praxim + metribuzin if planting metribuzin tolerant varieties. On later planted crops, I generally favour applying both the residual and contact herbicides together in a single spray approach, normally at higher rates depending on the overall weed burden. As always, timing is the key with a one spray strategy and I’m looking to spray when there’s good soil moisture around 3-4 weeks after ‘Prioritise crop safety’ Agronomists urge growers to be flexible and put crop safety at the forefront of potato weed control strategies. planting just before the ridges begin to crack. “Amongst the contact herbicide options, Gozai (pyraflufen-ethyl) offers effective control in most situations as long as weeds are not too large or deep rooted. To achieve optimum results from Gozai I recommend applying it at 0.4L/ha in minimum water volumes of 200L/ha with methylated seed oil (MSO) if applied alone and when weeds are larger than 4 true leaves. If Gozai is applied at the right coverage with an MSO then there should be no requirement for a follow up spray such as rimsulfuron” she adds. James Wrinch, an independent agronomist at East Suffolk Produce, endorses Fiona’s strategy advice and agrees that 2022 is likely to present some new and significant hurdles for UK growers. “Beyond the likelihood of more product losses there could also be a substantial rise in inflationary costs to growers - particularly on key inputs such as chemicals and fertiliser linked to rising energy prices,” he said. “Covering South Norfolk, East Suffolk and North Essex my main customer base are growers supplying either the wholesale or retail packing markets although I do have customers growing for export to the Canary Islands. “Key weed control challenges are when dealing with light land and when potatoes are in rotation with other root crops. I also have many farmers growing very early potato crops under fleece. This can often be tricky, given the need to get the residual herbicides on very quickly once planting has been completed. “On product choice for residual herbicides, both aclonifen and metribuzin, and to a lesser extent pendimethalin are all sound options. However, based on its outstanding crop safety record and reliability, my corner stone is Praxim when building early programmes. It’s uncomplicated so there’s no need to stress about varieties, following crops or soil types. “For later plantedmain crops onmessier fields, mymain go-to tankmix is Praxim+ aclonifen + Gozai. It’s a proven combination that will deal withweed control in 80-90%of the growing scenarios I encounter withinmy territory. “As a contact herbicide, Gozai performs well against most broadleaf weeds when applied at the correct rate of 0.4L/ha. Remember to keep water volumes at a minimum of 200L/ha and apply anMSO alongside Gozai to maximise the effectiveness of the product” he concludes. “On early chitted crops I prefer to get residual herbicides on as early as possible once ridges have settled and there is good moisture in the soil.” Fiona Law-Eadie, Agronomist James Wrinch Fiona Law-Eadie