Aspects of the Ecology of Two-Stem Feeding Willow Aphid Species.

Abstract

The giant willow aphid, Tuberolachnus salignus (Gmelin) (Lachninae, Lachnini) and the black willow aphid, Pterocomma salicis (Linaeus) (Aphidinae, Pterocommatini) are abundant in short rotation coppice willow plantations planted as biomass energy crops. Little is known about the interactions of these two species and this thesis investigates several important aspects of their ecology and biology.
I present studies of the direct and indirect effects of both species on host willow trees. The impact on willow yield and survival, both short and long term, brought about by aphid infestation are examined and discussed as is the impact on the host tree of honeydew deposition in the rhizosphere. Additionally I examine aspects of the host selection and performance of T. salignus and discuss this in the context of the possibility of co-ordinated management of several willow pests.
Pterocomma salicis benefits from ant attendance and I present an experiment demonstrating that ants also aid their dispersal. These two aphid species also have an intriguing association in which P. salicis appears to be a parasite of colonies of T. salignus, this relationship is investigated and discussed using both field observations and laboratory experiments.