Potato Review

www.potatoreview.com POTATO REVIEW MARCH/APRIL 2023 19 FLN/SPRAING TRIALS Produce Solutions’ Team Lead, James Lee, highlighted FLN and the associated issue of spraing can result in signi cant crop losses. “ e major challenge with FLN and spraing is that, unlike most other visual defects, suppliers can’t reduce the level of waste through grading/ sorting. e level of infection of spraing that will result in total crop failure is relatively low.” He added that spraing is a major issue for both packers and processors, which means a ected crops have no secondary market of any value. While skin blemished tubers could still be used for secondary packing or processing, crops with signi cant spraing have little outlet beyond stockfeed. “ e FLN and spraing pest/disease complex is a key factor in our agronomy advice and planning,” he advised. “It’s often very di cult to forecast when FLN and spraing are going to cause an issue. Soil sampling is not as straightforward as with PCN, while the presence of FLN doesn’t always result in TRV (spraing). is adds a level of complication to decisionmaking.” Potato processors impose a strict grading system for the acceptability of tubers with visible e ects of spraing, including the diameter and the length of the internal damage. For the FLN spraing trial, Produce Solutions assessed tubers for the percentage of visible damage to the cut surface, with ve categories from zero, to over 50% of area damaged. e use of Nemathorin at the label rate of 30 kg/ha produced a 160% increase in percentage of marketable tubers with an acceptably low level of spraing, compared to untreated. e use of uopyram in the trial, either applied at label rates in-furrow or overall and incorporated, provided no signi cant increase in acceptable yield over untreated. e trial also included application of Nemathorin at half-rate of 15 kg/ha, as used by growers for wireworm suppression, that gave a lower, but still a signi cant, 114% increase in the percentage of tubers acceptable for processing. Where uopyram was used in combination with half-rate Nemathorin there was no additional signi cant bene t. Andy pointed out the Shropshire site was speci cally selected for its history of FLN, with pre-trial testing revealing a population of 433 stubby root nematodes per litre of soil, including both Trichodorus and Paratrichodorus nematode speciesmost widely associatedwith spraing. e testing also showed the FLN to be carrying TRV. “ e trial results showed a clear correlation between the use of nematicides to target FLN and the reduction in the incidence of symptoms of spraing,” he highlighted. “ e most e ective nematicide, at the highest rate, gave the best result.” Further trials had shown where there was a lower initial population of FLN, the di erences were correspondingly less, but with the same result of reduced damage and greater proportion of acceptable yield with the Nemathorin treatment. “ at has con rmed the importance of accurate soil testing to identify the potential threat from FLN and the incidence of TRV in the population,” advocated Andy. “ e presence of FLN can initially be very patchy in a eld, before the population spreads. Where growers or agronomists identify weakened plants or crops with shorter, stubby roots, then GPS pinpointing or mapping the patches can facilitate more accurate soil testing when potatoes come around in the rotation again.” For potato growers facing multiple soil pests active at the same time, Nemathorin can also target potato cyst nematode and wireworm with the one application, he added. “Tubers are most susceptible to more damaging e ects of spraing from early TRV infection. FLN activity can also result in reduced root formation and make plants more susceptible to other stresses.” Andy Cunningham Spraing results untreated. Spraing results following Fluopyram in furrow. Spraing results following Nemathorin. Spraing FLN trial.