Genetic variation in susceptibility of Abiesbalsamea to Mindarusabietinus

Abstract

A northern Vermont provenance test containing 1 Fraser fir (Abiesfraseri (Pursh) Poir.) and 21 balsam fir (Abiesbalsamea (L.) Mill.) provenances was attacked by the balsam twig aphid (Mindarusabietinus Koch.) during 1977 and 1978. Balsam fir from eastern provenances had 15–60% greater incidence of attack and averaged nearly twice the crown injury than did that from western provenances. Trees from an Indian Lake, NY, provenance were injured most with an average of 27 and 62% of current-year shoots injured during the 1977 and 1978 infestations. Trees from an Isle, MN, provenance were injured least with an average of 2 and 9% of current year shoots injured during the 2 years. The relative distribution of injury among provenances was similar from year to year. Fraser fir suffered little or no injury and appears to avoid twig aphid attack when planted in the north because it begins growth after the aphid population has peaked. The concentration of β-phellandrene in twigs was strongly correlated with twig aphid injury in balsam fir, whereas height, date of budbreak, needle length, and concentrations of other monoterpenes were weakly or only indirectly correlated with twig aphid injury.