Influence of Tree Growth Rate, Shoot Size and Foliar Chemistry on the Abundance and Performance of a Galling Adelgid

• Published in: Functional ecology 1999-12, Vol.13 (6), p.859-867
• Main Authors: McKinnon, M. L., Quiring, D. T., Bauce, E.
• Format: Article
• Language: English
• Subjects: Adelges abietis; Adelgidae; Animal and plant ecology; Animal, plant and microbial ecology; Animals; Autoecology; Biological and medical sciences; Female animals; Fertilization; Forest ecology; Fundamental and applied biological sciences. Psychology; Human ecology; Insect ecology; insect–plant interactions; Leaves; Nymphs; parabolic plant module size–galler abundance relationship; phenols; Picea glauca; Plant gall; Plant stress; Plants; Protozoa. Invertebrata; tannins
• ISSN: 0269-8463; 1365-2435
• DOI: 10.1046/j.1365-2435.1999.00376.x

1. The abundance and performance of the Eastern Spruce Gall Adelgid, Adelges abietis, was evaluated on young, open-grown trees of White Spruce, Picea glauca, whose growth rates had been increased through fertilization or decreased through root-pruning. 2. In general, gall densities were highest on control trees and on mid-crown branches. Reduced galling success on fertilized trees was largely due to higher overwintering mortality of first-generation nymphs. Foliar magnesium, total tannin and total phenol contents were positively, and nitrogen and total monoterpene contents negatively, related to gall density and/or galling success. 3. Although short shoots were more abundant, shoot length was parabolically related to gall density. There was a non-significant parabolic trend between shoot size and galling success and volume. The number and average size of A. abietis females emerging from galls were positively related to gall volume, and realized fecundity was positively correlated to female size. Consequently, fitness was approximately twice as high for nymphs colonizing intermediate-sized than small or large shoots. 4. These results do not support the plant vigour or plant stress hypotheses. The results do, however, agree with predictions of the modified plant stress hypothesis for sucking insects. It is speculated that Adelges abietis lacks the necessary resources for successful gall formation on small shoots and is unable to produce a stimulus large enough to induce gall formation on large shoots.