Potential impacts ofTuberolachnus salignus(giant willow aphid) in New Zealand and options for control

Abstract

The giant willow aphid Tuberolachnus salignus was discovered in New Zealand in late 2013. Despite being a recent addition to the New Zealand fauna, the aphid is already widespread and abundant throughout the country. The giant willow aphid is expected to have negative impacts on host trees, primarily willows (Salix spp.), as has been observed elsewhere. All willows are exotic to New Zealand and a few have formal weed status, however many species are valued for multiple purposes, including flood protection, land stabilization, shelterbelts, and as early season pollen and nectar resources for honey bees. Tuberolachnus salignus presents a unique problem for New Zealand's thriving honey and honey products industries. Bees readily forage on the vast quantities of honeydew secreted by the aphid, however the honeydew contains melezitose sugar. The low solubility of this sugar results in honey crystallizing in the comb, making it difficult to extract and thereby reducing yield. It is also considered to be poor food for bees, and has been linked to bee dysentery and low overwintering survival. We elaborate on the potential complications for New Zealand as a result of the arrival of this new species and present options for its control and management.