Lupine Alkaloids as Larval Feeding Deterrents for Spruce Budworm, Choristoneura fumiferana (Lepidoptera: Tortricidae)

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Abstract
Twelve lupine alkaloids, eight from Lupinus polyphyllus (Lindl), were tested in feeding bioassays against sixth instar spruce budworm, Choristoneura fumiferana (Clemens). Feeding deterrence was found in the alkaloid fraction of L. polyphyllus extracts. Eight lupine alkaloids shown to be present in the extract were tested at the rate of 25 μg per feeding disc. Of these compounds, 13-trans-cinnamoyloxylupanine and 13- tigloyloxylupanine were highly deterrent, whereas lupanine, sparteine, 13-hydroxylupanine, tetrahydrorhombifoline, angustifoline, and 17-oxolupanine, were not. Four alkaloids not present in L. polyphyllus, lupinine, epilupinine, α-isolupanine, and lupinyl-trans-cinnamate, were not active at 25 μg per feeding disc. Clearly, there is wide variability in the response of spruce budworm larvae, which are not adapted to feeding on alkaloids, to various alkaloids within the same structural class. If this variability in response is general among herbivores, perhaps the presence of an alkaloid is not significant with regard to defense, whereas diversity in structure of alkaloids may deter generalist grazers.