Factors affecting willow leaf beetles ( Phratora vulgatissima ) when selecting overwintering sites

Abstract Leaf beetles are major pests in willow plantations used as short‐rotation coppice for biomass production. The beetles overwinter mainly outside the plantations. An understanding of the factors affecting adult leaf beetles seeking overwintering sites may provide information that could be valuable when developing methods to control the beetles. We conducted a field experiment in a willow plantation with a high abundance of the leaf beetle, Phratora vulgatissima . We positioned overwintering constructions (OWCs) made out of bundles of reed ( Phragmites australis ) outside the plantation. Leaf beetles preferred (i) to fly towards silhouettes; (ii) OWCs positioned 1.5 m above the ground compared with ones 0.5 m above the ground; (iii) OWCs orientated vertically compared with OWCs orientated horizontally; and (iv) reeds of a diameter of approximately 5 mm. Leaf beetle size was not correlated with reed diameter. It is concluded that the leaf beetle P. vulgatissima selects an overwintering site based on factors at both larger and smaller scales. The possibilities for using OWCs made of reed bundles as tools to monitor and control are discussed.