Influence of host genotype on Douglas-fir seed losses to Contarinia oregonensis (Diptera: Cecidomyiidae) and Megastigmus spermotrophus (Hymenoptera: Torymidae) in western Oregon
1989
Schowalter, T.D. | Haverty, M.I.
Seed losses to the Douglas-fir cone gall midge, Contarinia oregonensis Foote, and Douglas-fir seed chalcid, Megastigmus spermotrophus (Wachtl), were measured in a Douglas-fir, Pseudotsuga menziesii (Mirbel) Franco, clonal seed orchard and in a Douglas-fir progeny plantation in western Oregon. Seed losses to both insects differed significantly (P less than 0.05) among clones and among the progeny of selected parental crosses. Seed loss differed more than three times between least-infested and most-infested clones or progeny. Seed losses in the progeny plantation indicated that resistance to these two insects is a heritable trait, with greater resistance showing a tendency to dominate over lesser resistance. Insect responses to host genotype may be modified by factors associated with the position of the tree within the stand. Implications of these results for tree improvement programs and seed orchard management are discussed.
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