Potential beetle vectors of Sirococcus clavigignenti-juglandacearum on butternut.
To identify potential beetle (Coleoptera) vectors of the butternut canker fungus (Sirococcus clavigignenti-juglandacearum), beetles were collected from butternut (Juglans cinerea) trees and freshly cut logs and branches in Vermont from 1997 through 1999. At least 17 species of beetles, representing eight families, were found to carry conidia of the pathogen. Species most commonly collected and most frequently carrying the fungus were Acoptus suturalis (Curculionidae), Astylopsis macula [? Amniscus maculus] (Cerambycidae), Eubulus parochus [? Cryptorhynchus parochus] (Curculionidae), and Hyperplatys maculata (Cerambycidae). In 1999, 64, 74, 37, and 52% of these species, respectively, were carrying conidia. These beetles were often collected from dead butternut stems and branches upon which the fungus was fruiting and were less frequently found in crowns of living butternut trees. The butternut curculio (Conotrachelus juglandis) (Curculionidae) was found creating feeding and oviposition wounds on new shoots in crowns of butternut trees. Six to eleven percent of curculios collected carried the fungus. Species of Nitidulidae were observed crawling on logs or burrowing into cankers and curculio wounds. Six to seven percent of the nitidulids, Cryptarcha ampla and Glischrochilus sanguinolentus, carried conidia in 1999, and 31% of G. vittatus carried the fungus in 1998. Additional study is necessary to learn how consistently any of these beetles move from diseased to healthy tissue of butternut and vector conidia of S. clavigignenti-juglandacearum.