NUTRITIONAL STUDIES OF EASTERN SPRUCE BUDWORM (LEPIDOPTERA: TORTRICIDAE): II. STARCHES

Abstract

Amylopectin added to a sugar-free wheat-germ diet was equal to or better than sucrose as a carbohydrate source, and appears to be readily utilized by the eastern spruce budworm (Choristoneura fumiferana (Clem.)). Larval growth on diets containing dextrins or potato starch shows that they are partly utilized. Starches from other sources, including those isolated from mature balsam fir (Abies balsamea (L.) Mill.) or white spruce (Picea glauca (Moench) Voss) needles, are not utilized to any extent, on the basis of larval growth on diets to which they have been added.Sixth-instar budworm reared on artificial diets contain amylase(s) in midgut and salivary gland homogenates, which show a low rate of digestion of starches from host foliage. However, the presence of appreciable starch in frass from foliage-fed insects and the apparent low utilizability of foliar starch indicate that the latter is not an important nutrient for the budworm under natural conditions.