Attack on Black Walnut Trees by the Ambrosia Beetle Xylosandrus germanus (Coleoptera: Scolytidae)

Abstract Differences in susceptibility of black walnut ( Juglans nigra L.) trees to attack by the ambrosia beetle Xylosandrus germanus (Blandford) and the long-term effects on subsequent growth were studied in a southern Illinois plantation from 1978 to 1980. The percentage of trees attacked differed by geographic source: Kentucky trees were more susceptible and Kansas, Missouri, and Tennessee trees less susceptible. All trees attacked were less than 3.25 m in height and 4.25 cm in diameter. Trees that were attacked had slower height growth rates during the growing season before attack, and sharply reduced height and dbh growth rates during the year of attack, than trees not attacked. None of the attacked trees had died by the end of the second growing season after attack. At this time, the height growth rates of attacked trees were higher than those of unattacked trees and the dbh growth rates in both groups of trees were the same. Forest Sci. 30:864-870.