Request for Information: North American Botanic Gardens

24 October 2018

The European and Mediterranean Plant Protection Organisation (EPPO) have requested information on the America wood borer Agrilus bilineatus on European oaks and Castanea species. This information will be invaluable to determine the risks to European trees of this pest.

Botanic Gardens and Arboreta in the Eastern United States and Canada that have already recorded damage due to this insect on European species of oak and chestnuts (in particular Castanea sativa) are requested to provide information.

Information can be submitted using the Plant Health Checker

Signs and symptoms of infestation (in chronological order of first appearance) are

• Tortuous traces of larval galleries filled with frass (Haack, 1985), which are typical for the genus Agrilus. Remark: early instars (first and second) tend to tunnel in any direction, but late instars (third and fourth) tend to tunnel across the wood grain (Chapman, 1915).

• Cracking/swelling of the bark: Development of ridges or swelling on the bark surface as a result of callus tissue developing over the larval galleries occasionally occurs on thin-barked trees, especially on branches, but less so on the trunks.

• D-shaped exit hole as in semicircle (about 5-mm wide) (Haack & Acciavatti, 1992). D-shaped exit holes are also produced by other Agrilus species.

• Wilted foliage on scattered crown branches in late summer (Haack & Acciavatti, 1992). The wilted foliage turns brown and remains attached for several weeks or even months. Such branches will not produce new foliage in subsequent years.

• Dieback and dead trees: Tree death can occur in a single year, especially during A. bilineatus outbreaks, but tree death over a two to four year period is more common. None of the symptoms above are specific to A. bilineatus.