Effects of resin flow and monoterpene composition on susceptibility of lodgepole pine to attack by the Douglas-fir pitch moth, Synanthedon novaroensis (Lep., Sesiidae)

Resin flow differed significantly among three of six clones of lodgepole pi ne seed orchard trees, but did not differ among the clones categorized as s usceptible or resistant to attack by the Douglas-fir pitch moth. A stepwise regression analysis identified delta-3-carene, cyclohexene, and alpha-terp inolene as significant compounds, explaining 49.9% of the variation in the number of attacks per tree, delta-3-Carene alone explained 41.8% of the Var iation in the regression, and analysis of variance showed that resistant cl ones consistently had high relative amounts (> 17.9%) of this compound, whe reas susceptible clones had low amounts (<10%). The significant effect by c yclohexene and alpha-terpinolene in the stepwise regression appeared to be due to a correlation between alpha-terpinolene and delta-3-carene in severa l clones, and that cyclohexene was only present in one clone, rather than a ny discernable biological relationship. Limonene co-eluted with beta-phella ndrene, so its role must be determined by additional study.