Effects of gall formation by Dryocosmus kuriphilus on the growth of the Japanese chestnut tree (Castanea crenafu) were investigated from 1988 to 1989 using 15 wild trees. Mean leaf area on galled shoots currently expanded was about a half that on ungalled shoots. Galled shoots were lower than ungalled shoots both in biomass ratio of leaf/shoot and in mean number of winter buds per shoot. Bud expansion on galled shoots was less successful. Total biomass of current shoots diminished under heavy infestation with D. kuriphilus. Thus, D. kuriphilus not only retarded the development of photosynthetic organs but also reduced the biomass production of host trees in the next year. This may be a causal mechanism of biomass decline in gall-infested trees.

Optimal clutch size of the chestnut gall-wasp, Dryocosmus kuriphilus Yasumatsu (Hymenoptera: Cynipidae), was examined in galls on wild and resistant chestnut trees in 1988 and 1989. The rate of escape success of newly-emerged adults from galls was an average of 60%, irrespective of cell numbers per gall. Dry mass per cell of a gall (as an index of nutritive condition) decreased with increasing cell number per gall, but was proportional to the mean number of mature eggs of new adults per gall. The number of cells per gall that occurred most frequently did not agree with that attained by the maximum survival rate from young larva to adult emergence of the gall-wasp. This discrepancy was examined from the viewpoint of three factors: 1) quality of offspring, 2) defensive response of the host plant causing mortality of the gall-wasp before cell formation, and 3) fitness per gall vs. fitness per egg. It is concluded that the third factor is most likely to be the one best in explaining the discrepancy.

No abstract

No abstract

To determine the viability of hot water emasculation for Acacia auriculiformis, spikes composed of about 100 flowers were soaked in hot water at varying temperatures (45-60°C) and for varying lengths of time (5 s to 7 min) prior to anthesis. The rate of squashed polyads, each of which consisted of 16 pollen grains, and the germinating rate on media, decreased with temperature and time. A mating test suggested that the rates of adhering polyads per stigma and germinating polyads per stigma were lower in the self-pollination of soaked spikes than in that of normal spikes. On the other hand, the number of matured pods was not significantly different in the mating between the spikes receiving the soaking treatment ($) and the spikes receiving no treatment (#) compared with the mating between normal spikes. Although further research is needed to determine the optimal treatment conditions, these results suggest that soaking spikes into hot water, especially at 50°C for 45 s, 54°C for 15 s, and 56°C for 10 s, is an effective emasculation technique.