Potato Review

www.potatoreview.com POTATO REVIEW MARCH/APRIL 2022 11 VIRUS / APHIDS F URTHER restrictions on insecticide use and a rise in potato leaf roll virus (PLRV) over the past two seasons are reinforcing the need to accelerate adoption of integrated pest management (IPM) methods in 2022. Over recent seasons, seed potato growers across Great Britain have been paddling against the current of insecticide resistance in aphid populations, insecticide product losses and, consequently, rising levels of non- persistent potyvirus like PVY. Recent industry communications from Belchim and Syngenta, both of whom market products containing ISK’s active substance flonicamid, have advised growers not to use the insecticide in potatoes until further notice. MRL issues The issue relates to itsmaximum residue level (MRL) andmanufacturers cannot guarantee there won’t be exceedances, evenwhere the product is used in strict accordance with the product label. There is already a label restriction which permits flonicamid being used with adjuvant Faster uptake of IPM required As more restrictions are placed on insecticide use for 2022, Potato Review reveals the implications and gets some advice on how to minimise virus transmission by aphids this year. oils, a practice which resulted inMRL exceedances inThe Netherlands a few years ago. It is understood that ISK IS working on raising the MRL in potatoes to solve the problem but acquiring the relevant data to submit to HSE-CRD will take time and there is no guarantee the situation will be sorted for the upcoming growing season. Scottish Agronomy’s Eric Anderson says systemic insecticides like flonicamid are targeted at the main colonising aphids of Myzus persicae (peach potato aphid) and Macrosiphum euphorbiae (potato aphid). In recent seasons, these species have started their flights early, arriving in potato crops soon after emergence with the threat of spreading virus. Slow burndown At the other end of the season, slower burndown of crops following the withdrawal of diquat and the potential for regrowth where desiccation has not been thorough have also increased virus risk. Eric points out that Certis product InSyst (acetamiprid) is set to be the sole systemic insecticide left at growers’ disposal this year but with a new label to work through. InSyst product in the market this year will be carrying one of two MAPP numbers. Packs with the old MAPP number 13414 can be used in the same way as before and a new MAPP number 19873 has new conditions of use. The new label still allows two applications of the product in seed crops, but these cannot be used before BBCH 40 (tuber initiation) or after BBCH 89 (early senescence). An additional specific requirement to protect non-target insects/arthropods is that it must not be applied after July 31ST, which precludes any late season use. Finally, the interval between the two applications in seed crops has been extended from seven to 21 days. ➜ Wheat straw was better than barley straw as a mulch on potato beds, as it breaks down much faster and reduces the risk of problems at harvest Agronomist Eric Anderson.