BOTHWELL, BRYAN, CHERYL L. LOVELESS, RAYMOND R. BARD, AND MICHAEL D. SNOW.* Department of Chemistry and Physics, Department of Biology, University of Portland, Portland,OR 97203. - Monoterpene levels in Douglas-fir needles in relation to needle midge infestation.
The Douglas-fir Needle Midge (Contarinia pseudotsugae) is a
serious pest of Douglas-fir Christmas trees in the Pacific Northwest.
In this study, levels of monoterpenes were measured in needles of
current (1999) and previous year’s (1998) growth from infested and
uninfested branches of Douglas-fir (Pseudotsuga menziesii
(Mirb.) Franco) trees. Samples were taken at approximately bi-monthly
intervals from May through October. Monoterpenes were identified and
quantified using gas chromatography/mass spectroscopy. Nine
monoterpenes occurred regularly in all trees. Beta-pinene was the most
prevalent compound in all samples. Total terpenes were higher in 1998
age-class needles than the 1999 age-class needles in the early season.
Camphene and bornyl acetate were higher in uninfested needles than in
infested 1999 age-class needles. These two compounds are known to
decrease budworm larval growth and may be important in influencing
needle midge host choice.
Key words: Douglas-fir Needle Midge, Douglas-fir, gas chromatography, monoterpene