Influence of Host Foliage on Development, Survival, and Fecundity of the Gypsy Moth 2

Gypsy moth, Lymantria dispar (L.), larvae reared on leaves of various tree species differed in survival, development rate, and fecundity. White oak and red oak generally produced greatest survival, most rapid development, heaviest pupae, and highest fecundity. White ash caused 100% mortality. Beech, red maple, sugar maple, and Eastern hemlock were intermediate in their effects. Rearing larvae on leaves obtained from trees 1 or 2 mo after the normal hatch date increased mortality to 95–100% on all diets except white oak; on white oak, fecundity of survivors dropped to ca. half its value on young leaves. Leaves of all 7 tree species declined in water and nitrogen content and increased in toughness between early May and late June, which may explain partly the decreased survival of larvae fed on more mature leaves. In preference tests, newly emerged 1st-instar larvae chose white oak over red oak, but chose the latter over most other species. The adverse effects of feeding on non-oak host leaves may mean that as the proportion of oaks declines in an area, the gypsy moth population will also decline. This could explain the observation that the most severe gypsy moth outbreaks occur in areas where the insect is newly introduced and favorable host species are abundant.