Early-season use of insecticides for management of woolly apple aphid (eriosoma lanigerum) in nelson apple orchards

Abstract

A spray strategy to control woolly apple aphid (Eriosoma lanigerum, WAA) was assessed on apple orchards in Nelson. Carbaryl, applied for fruit thinning, was either sprayed alone or combined with diazinon on 'Braeburn' apples at four orchard sites infested with WAA. The diazinon plus carbaryl treatment reduced WAA levels and there were lower numbers of WAA-infested shoots with considerably fewer colonies on branches and shoots in November. Numbers of WAA colonies on shoots in January were 50% lower overall in the diazinon plus carbaryl treatment. There was an initial decline in numbers of the WAA parasitoid, Aphelinus mali, in both treatments, but they increased steadily during the season and high levels of parasitism were evident by harvest. The parasitoid was able to suppress the lower populations of WAA in the diazinon plus carbaryl treatment and this resulted in significantly lower levels of WAA shoot and fruit infestation and bud damage in late March.