EFFECTS OF GALL FORMATION BY DRYOCOSMUS-KURIPHILUS YASUMATSU (HYM, CYNIPIDAE) ON THE GROWTH OF CHESTNUT TREES

Effects of gall formation by Dryocosmus kuriphilus on the growth of th e Japanese chestnut tree (Castanea crenata) were investigated from 198 8 to 1989 using 15 wild trees. Mean leaf area on galled shoots current ly expanded was about a half that on ungalled shoots. Galled shoots we re lower than ungalled shoots both in biomass ratio of leaf/shoot and in mean number of winter buds per shoot. Bud expansion on galled shoot s was less successful. Total biomass of current shoots diminished unde r heavy infestation with D. kuriphilus. Thus, D. kuriphilus not only r etarded the development of photosynthetic organs but also reduced the biomass production of host trees in the next year. This may be a causa l mechanism of biomass decline in gall-infested trees.