Potato Review

56 POTATO REVIEW NOVEMBER 2021 ROLLER TABLE TREATMENT E XPERTS agree that there is room for improvement on liquid seed treatment use and store hygiene practices to weather a perfect storm of storage diseases like dry rot, gangrene, skin spot and silver scurf. Previously in Potato Review (September/ October, p19-21), it was highlighted that risk assessments to establish the need for liquid fungicide tuber treatments within the seed industry could be much better. Also noted was the fact that protectant treatments such as Gavel (imazalil) should be applied as early as possible in the storage period to get the best activity on key diseases and avoid significant losses. The earliest opportunity to apply a seed treatment presents itself at harvest or on a roller table when split grading into store, but independent potato consultant Paul Overton says not all seed producers are set up to execute either. This should not dissuade growers from using a seed tuber treatment at the next window of opportunity, which opens during first grading. For seed exported to non-EU countries like Egypt, this is late October onwards before shipping for December planting, then for the domestic market from early December through until spring. Avoid “naked” seed Over the past five years there have been more producers choosing to leave seed “naked” and only treating seed with pre-planting Keep seed tuber disease control rolling to season’s end In the second article of our three-part series, Potato Review offers advice on best practice roller table treatment and highlights the importance of grading line and store hygiene in keeping good seed healthy over winter. products aimed at Rhizoctonia control before delivery to customers, according to Paul. This is increasing the risk of storage diseases – pathogens which find their way into tubers through damaged skin – developing, with higher levels seen in seed over recent seasons. Combined with an increasing number of thin-skinned varieties being grown and tubers being harvested in warm conditions more frequently, increasing the risk of damage, it is creating a perfect storm for crop losses. Paul says in this second phase, black scurf control is unhelpfully dominating conversations, but dry rot, skin spot gangrene and silver scurf are still a big risk and adds that there is no reason not to add protection at that stage. “Gavel can even be used in sequence in Rhino ( flutolanil) or Maxim ( fludioxonil), as both products have enough persistency to protect against black scurf post-planting, even when applied at first grading,” he said. While integrated management methods like good skin set, minimising harvest damage and good ventilation and curing in store will all help against storage disease, they still need support from chemical control, Paul said. “Whenever you move or grade seed, there is a risk of scuffing and damage and a treatment like Gavel for about £5/t will prevent any further infection. You wouldn’t put a topcoat of paint on without applying a primer and Gavel gives you a red oxide effect against those base diseases until seed is planted,” he said. Optimise coverage When treating during this second window of opportunity, growers will be using a roller table setup of some kind, but the type and quality of the equipment will have a big bearing on product efficacy. Paul says applying liquid seed tuber treatments is all about coverage and active substance retention on the target and static hydraulic or spinning discs setups are still used by some seed producers. While this method is better than applying no treatment at all, where disease risk is identified, they can result in suboptimal results. He points out that application equipment has moved on considerably since many of these systems were installed. Paul Overton Harry Raley David Turner