Potato Review

www.potatoreview.com POTATO REVIEW SEPTEMBER/OCTOBER 2021 19 SEED CARE S EED producers could be putting the health of their product in jeopardy by not using robust disease risk assessments and appropriate seed potato treatments, a recent industry survey suggests. Last winter, SAC Consulting conducted a study of seed potato treatment practices in Scoltand covering around 100,000t of seed, a significant sample equating to one fifth of total UK production. The advisory group’s potato consultant, Kyran Maloney, who conducted the survey, said it was kept simple to encourage as many growers to participate as possible. Just three questions were asked. The first aimed to find out which stocks seed growers would treat with a fungicide before or during storage to control diseases such as gangrene, skin spot, dry rot and silver scurf. “It was hoped this would give us an Risk assessments must improve in store In the first of three articles, Potato Review takes a look how seed producers approach the first phase of seed care as tubers are harvested and loaded into store. Can improvements be made to keep good seed healthy? indication of whether growers treat everything regardless, carry out risk assessments and treat only when a problem is identified, or perhaps only treat for certain customers,” he said. The second question asked at what point they treated: At harvest, when split grading into store, or later on when fulfilling customer orders. Finally, the survey asked what equipment was used to apply seed potato treatments. Risk assessments More than half of the respondents were treating everything and only a minority were conducting a thorough risk assessment before using the two available treatments: Gavel (imazalil) or Storite (thiabendazole). A risk assessment would take into account risk factors such as varietal susceptibility, along with seasonal issues specific to the crop. About 15% of growers weren’t using a seed treatment at all and the remainder were treating at their customers’ request, or treating some stocks and not others. Kyran said these responses show that fungicide seed treatments are often not being applied following a risk assessment (see How to conduct a seed treatment risk assessment), with the majority using them routinely rather than in a targeted way. “A lot of stocks will need treatment, but I would like to see more of them applied after risk assessments. Routine use is not good for stewardship or sustainability and there is no point in applying fungicides where you don’t need them,” said Kyran. Treatment timing Data from the survey suggested that more than half of respondents using a seed treatment did so “at harvest”, while a quarter were doing it “at grading”. Finally, a handful of growers were split grading ahead of store loading, which means they harvest into bulk trailers, separate seed into the relevant size fractions and “Routine use is not good for stewardship or sustainability and there is no point in applying fungicides where you don’t need them.” ➜ Half of seed growers responding to a recent SAC Consulting survey said they used fungicide seed treatments at harvest, a practice which may be compromising product efficacy against key storage diseases.