The blueberry gall midge (Dasineura oxycoccana) is a damaging pest of UK blueberry crops. The pest was first confirmed in the UK around 10 years ago but it is now widely found across the country. It is most important in newly planted crops and during the first two-to-three years of establishment.
It lays its eggs in the growing points of shoots and the larvae live in leaf galls in the shoot tips, giving rise to leaf distortion and blackening of the buds, which are killed by the attack. This dieback reduces the numbers of buds produced for the next year's crop, thus resulting in yield reduction the year after the attack.
AHDB Horticulture-funded project SF 126 employed scientists at NIAB EMR and the Natural Resources Institute to identify the female-produced sex pheromone of the blueberry gall midge. They then synthesised it, allowing it to be used in commercial traps that are available to growers.
It is best to deploy the traps before any signs of damage are seen in the spring and it is best to place them as near to the ground as possible to maximise catches. The research has identified that a threshold of 10 male midges per trap per week is a suitable level at which to initiate control measures.
Several crop-protection products were tested to assess their efficacy at controlling blueberry gall midge. Thiacloprid (Calypso) and pyrethrins (Spruzit) are the only products currently approved for use against gall midge on blueberry. Of these, only thiacloprid proved effective, although accurate timing of application is essential. In the trials, both chlorpyrifos and lambda-cyhalothrin also reduced some larvae and galling, but results were not consistent between spray dates and varieties.
For details on all AHDB Horticulture activity, see horticulture.ahdb.org.uk.