Spatial extent of traumatic resin duct induction in Japanese cedar, Cryptomeria japonica D. Don, following feeding damage by the cryptomeria bark borer, Semanotus japonicus Lacordaire (Coleoptera: Cerambycidae)

In order to understand the role of traumatic resin duct formation in the inner bark as a host defense reaction to larval feeding damage, six 11-year-old Japanese cedar trees (Cryptomeria japonica) were inoculated with larvae of the cryptomeria bark borer (Semanotus japonicus). The spatial extent of this defense reaction was measured one, two, and three months after inoculation by examining the occurrence of newly formed resin ducts in more than 720 bark samples per tree. Two types of spatial extent of the responding inner bark area were observed in the experimental trees: localized and systemic. In four trees, showing the localized response, most of the induced resin ducts were confined to the proximity of each larval gallery, and the area of responding inner bark was positively correlated with the substitutive value for larval gallery length. In two other trees, showing the systemic response, induction of resin ducts was not localized but extended throughout the whole trunk.