Root- and stem-colonizing insects recovered from eastern white pines with procerum root disease

Abstract

In 1988, eastern white pines (Pinusstrobus L.) from four southwestern Virginia Christmas tree plantations symptomatic of infection by Leptographiumprocerum (Kendr.) Wingf. were assigned to one of four symptom categories based on crown color and resin exudation at the root collar. A fifth category was added in 1989 and 1990. From each plantation, the root system and the lower stem of one tree in each symptom class was excavated monthly and examined for fungi and insects from June to September in 1988 and 1989 and from April to September in 1990. Larvae of two weevil species, Hylobiuspales (Herbst) and Pissodesnemorensis Germ., were recovered with L. procerum from 23, 17, and 21% of the trees in all symptom classes in 1988, 1989, and 1990, respectively. Pre-emergent adults of both weevil species contaminated with L. procerum were also recovered from excavated stems. Bark beetle genera (family Scolytidae), including Pityogenes, Xyleborus, Orthotomicus, Ips, and Pityophthorus, were recovered with L. procerum from 10, 11, and 8% of diseased trees with advanced symptoms in 1988, 1989, and 1990, respectively. The association of these insects, especially H. pales and P. nemorensis, with L. procerum throughout the decline of the host adds further evidence that they may act as vectors of the fungus.