Occurrence and development of Eucryptorrhynchus brandti and E. chinensis (Coleoptera: Curculionidae) on Ailanthus altissima trees subjected to different levels of mechanical damage.

Eucryptorrhynchus brandti(Harold) andE. chinensis(Oliver) are herbivores ofAilanthus altissima(Mill.) Swingle (tree of heaven) in China.Eucryptorrhynchus brandtihas been recommended as a potential biological control agent ofA. altissimain North America. In China, the majority of adults of both species were found on tree trunks 0–5 m above the ground, from May to September. In October and November, most adults were found at the base ofA. altissimatrees. Trees were subjected to different levels of mechanical injury: very low mechanical injury, one to two 0.015 m2bark sections were removed; low, two to four bark sections were removed; moderate, 8 to 22 bark sections removed; high, tree was girdled; and extreme, tree was felled and the remaining stump was sampled. Very low and low mechanical injury trees had very few adult emergence holes with few larvae developing beyond the first or second instar after 29 months. The health of these trees remained good. An increase in adult emergence holes occurred in moderately injured trees that appeared as healthy as very low to low mechanically injured trees. This may indicate that only a small increase in tree stress can increase the adult emergence rate and thus hasten a decline in tree health. Moderate, high and extreme mechanically injured trees had significantly more emergence holes/m than very low and low injured trees and late larval stages were present. The development ofEucryptorrhynchusspecies was more successful the greater the degree of mechanical injury. Based on this study bothEucryptorrhynchusspecies appear to be secondary pests ofA. altissimain China. [ABSTRACT FROM PUBLISHER]