Interactions between a fungal pathogen, foliar properties, and generalist herbivores

American [Castanea dentata (Marsh) Borkh.] × Chinese [Castanea mollissima Blume] chestnut (Fagac, ae) hybrids are a novel system in which to study influences of phytopathogenic fungi and woody plant hybridization on herbivore susceptibility, as the hybrids are well characterized with regard to resistance to the chestnut blight fungus [Cryphonectria parasita (Murr) Barr (Endothia) Diaporthales: Valsaceae] and variability is present. We chose two groups of resistance-rated backcross chestnut that shared an F1 parent and had different American parents. Foliage from both backcross groups and the parent trees was sampled on three dates for use in feeding assays with gypsy moth larvae [Lymantria dispar (L.) [Lepidoptera: Lymantriidae], adult Japanese beetles [Popillia japonica Newman (Coleoptera: Scarabaeidae)], and fall webworm larvae [Hyphantria cunea Drury (Lepidoptera: Arctiidae)], respectively. Foliar analyses were performed concurrently and included carbohydrate, tannin, and nitrogen content, toughness, and density. Blight resistance had almost no effect on herbivore performance or foliar chemistry. When the parent trees and backcross groups were compared, however, significant differences in gypsy moth performance and Japanese beetle consumption were evident. There were no differences in fall webworm consumption. Most foliar characteristics measured differed among chestnut genotypes at some point in the season, and all varied seasonally. No clear pattern emerges with respect to the relationship among blight resistance, herbivore susceptibility, foliar properties, and plant genotype, and more research is needed to separate these effects.