The distribution pattern of two juvenile hormone related compounds in Fraser fir and the induced response to a balsam woolly adelgid infestation

Two juvenile hormone related compounds (JRCs), juvabione and dehydrojuvabio ne, were isolated from Fraser fir, Abies fraseri (Pursh) Poirit. Both juvab ione and dehydrojuvabione concentrations had large variations across the te sted trees and within trees. Juvabione, but not dehydrojuvabione, was much higher in stemwood then in branchwood. There was no significant difference in either chemical in relation to high, low, or middle branch position. To determine if juvabione concentration was influenced by an infestation of ba lsam woolly adelgid, Adelges piceae Ratz., branches from infested and uninf ested 11-year-old Abies fraseri with were sampled at the bottom, middle, an d top branches of each tree. While mean juvabione concentrations for each i nfested fir were higher than their uninfested counterparts, only the infest ed middle tree sections had mean juvabione values that were substantially h igher (p = 0.078) than the corresponding uninfested tree section of all the infested firs. The two infested Abies fraseri that maintained apical domin ance demonstrated the highest upper branch levels of juvabione of all the i nfested. These results indicate that juvabione may be induced in small Abie s fraseri in response to adelgid attack. Trees that produce large quantitie s of this compound may possess tolerance to the adelgid. Further research i s needed to elucidate this possibility.