Potato Review

www.potatoreview.com POTATO REVIEW MARCH/APRIL 2021 43 APHID CONTROL “We are seeing shifts in sensitivity to pyrethroids such as lambda-cyhalothrin, and there is already resistance in a number of these aphids.” “The situation demands that we make better use of Integrated Pest Management (IPM) to protect the virus health of seed and ware potatoes.” Planting wildflowers in tramlines can provide habitats for their natural enemies; such as hoverflies, ladybirds, lacewings and parasitic wasps. “Insect counts in trials have found an important increase in numbers of adult natural enemies within ower strips, with hover ies up by 339%, ladybirds 177% and lacewings 233%, compared with potato controls. Cornflower, common vetch and yarrow worked well as banker plants by providing the correct density and diversity of habitat for the predators and parasites, he reports. Timing of planting needs to be factored in so that plants can sufficiently support the natural enemies and deliver them to the crop when they are most needed. “ is is because of the lag period as natural enemies take time to build their numbers.” The distance the predators will travel into the crop also impacts on predators’ efficacy, and the estimated maximum distance is 50m, so using the tramlines helps biocontrol. “Better knowledge of the roles biology, ecology and evolution play, will provide new insights to help make aphid and potyvirus control more effective. A holistic IPM approach integrating both traditional and modern tools will improved on-farm biodiversity and contribute to producing high health seed health.” Sowing spring barley around headlands of seed potato fields can help to reduce virus incidents. Measures to boost the presence of natural enemies like ladybirds is encouraged. “ ese e ectively provide ‘landing strips’ for aphids who tend to land in higher numbers in these areas. is is particularly acute in second and third generation (FG2 and FG3) seed potatoes. “Cereal purge strips or spring barley borders are readily adaptable to current production practices, although the greatest bene ts in reducing PVYN incidence may occur in smaller blocks of Pre-Basic seed potatoes. “Where aphids rst land in the surrounding cereal crop, this ‘cleans’ the aphid stylet of PVYN and other potyvirus including PVYO, PVA and PVV before they progress onto the seed potatoes.” ‘Shifts in sensitivity’ Once aphids are in the crop, reliance on a single mode of action and widespread use of pyrethroids risks elevating selection pressure for resistance, warns Eric. “We are seeing shifts in sensitivity to pyrethroids such as lambda-cyhalothrin, and there is already resistance in a number of these aphids, including the peach potato aphid (Myzus persicae), willow carrot aphid (Cavariella aegopodii) and English grain aphid (Sitobion avenae). In addition, research conducted in Ireland led by Teagasc Research O cer Dr Lael Walsh have found sensitivity shift to pyrethroids in the bird cherry oat aphid. “We do not know whether the single clone tested in Ireland is common in Scotland.” “But with prevailing westerly winds, the risk of its arrival is certainly heightened.” When pyrethroids are used, Eric advises using full manufacturer recommended rates, cautioning that blanket spraying has a negative e ect on bene cials.