RELATION BETWEEN ATTACK BY XYLOSANDRUS GERMANUS (COLEOPTERA: SCOLYTIDAE) AND DISEASE SYMPTOMS IN BLACK WALNUT

Abstract

Xylosandrus germanus (Blandford) (Coleoptera: Scolytidae) is an ambrosia beetle that occurs in Japan, Korea, the Kuril Islands, Vietnam, Taiwan, China, Central Europe, and the United States (Nobuchi 1981). Unlike most ambrosia beetles, it will attack apparently healthy trees and those that are dying or recently dead (Weber 1982). It has been associated with plants infected with pathogenic fungi, including black walnut (Juglans nigra L.) infected with species of Fusarium (Anderson and Hoffard 1978; Kessler 1974); reported symptoms include cankers, wilting and dieback, and sprouts. We found black walnut with wilting and dieback symptoms in southern Illinois in spring 1978 and central Tennessee in spring 1980. Subsequent examinations showed that X. germanus was present and apparently closely associated with the disease symptoms because of the number of diseased trees that also contained X. germanus pinholes. Therefore, we decided to study the relation between X. germanus attack and disease symptoms in black walnut.