Potato Review

24 POTATO REVIEW SEPTEMBER/OCTOBER 2020 BLACKLEG CONTROL Can improvements be made from storage to planting? Improved storage has made a huge di erence in reducing the amount of blackleg found, but potentially a weak link in the chain is moving seed potatoes from store to the eld where they are planted, Ian suggests. “Usually they have to be transported, and are not then planted straight away, so they have to be stored. We know that is not always in a high quality store. ey can even be left in the farmyard covered by tarpaulin for a couple of weeks before planting. “So what happens to the amount of bacteria on the tubers from coming out of storage on the seed farm to being planted? What happens to the temperature and moisture as these are the two things that really a ect bacterial levels after leaving the seed farm, and how are they transported? Are boxes or poly bags di erent? We’ve got some basic evidence that boxes might be better than poly bags.” crop at any time during development and then use the nematicide Velum Prime ( uopyram) to keep the nematodes at bay and potentially control blackleg.” e project is also going to investigate whether di erent types of cover crops increase or decrease bacterial levels and blackleg disease. “We have a suspicion that Pectobacterium might live better on some species than others – that’s certainly true of weed species. “So we’re going to look at the four main groups of cover crop – brassica, grass, legume and non-legume broadleaf – and see whether any increase or reduce the bacterium in the soil prior to planting potato.” e ultimate aim will be to pull that together with other research into a decision support tool for risk management and avoidance strategies. “One part of the tool will evaluate what is the risk of blackleg if we do nothing– what’s the likelihood of it occurring or spreading, and the impact on both the crop and the economics. “And then it will look at the mitigated risk – what’s the impact of doing something – what happens if we use a cover crop, manage our irrigation to acceptable levels, use a tolerant variety? “We hope to put this all together and a lot more to come up with a decision support tool that is usable for growers.” Recommended blackleg control measures In- eld Away from the eld · Plant clean seed · Clean equipment (including graders) · Keep weeds to a minimum · Keep tubers cool & dry – storage · Avoid over-irrigation · Monitor temperature & humidity in store · Burn down e ciently · Be vigilant once tubers are out of storage (transport) · Harvest as early as is practical “We’re almost certain that any disease resistance or tolerance you see in the field to blackleg is from a collection of genes working together.”

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