Tree hospitals have a relatively short history in Korea, since the first tree hospital was established in 1976. Nowadays 42 are counted as kinds of tree hospitals, that is, 12 belongs in the public, 19 in the private, and 11 in the sections of landscape gardening firms. These tree hospitals have not been under any government regulation until May 31, 2003. However, after June 1, 2003, every tree (Namoo) hospital with its sign is demanded by the regulation to employ at least one tree doctor qualified in tree health. And it is expected that, this kind of regulation will substantially improve the quality of tree hospitals in Korea in the future. Besides Korea Forest Service, Korea Culture Service requires private companies to employ one or more specialists qualified in tree health for the care of old and/or preserved trees e.g., those desingated as natural monuments. For the purpose to provide well-qualified tree doctors to tree hospitals, it is urgently demanded to educate peoples working on tree health in the field of landscape gardening.

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Population dynamics of maple aphids was monitored on four Acer palmatum trees for 13 years, and the effects of natural enemies and phenology on the population were analyzed. Study site (plot 12) and method were shown in Furuta et al. (1984). (1) Five generations were found usually in a year ; stem mother, its progeny, dimolt, autumnal winged female and its progeny. (2) The abundance, day-numbers (Ruppel 1983) for whole autumn population had a positive correlation with that for the following spring. But, the day-numbers for whole spring population had no correlation with that for the following autumn. (3) Day-numbers for autumnal winged females had a negative correlation with the time of first appearance of winged females in the autumn. (4) When peak number of stem mothers became larger, the time of the first appearance of syrphid larvae became earlier. Then, reproductive rate of stem mothers decreased. Syrphids made the reproductive rate of the aphid decrease density dependently. (5) Ln [dimolt numbers] minus In [progeny numbers of stem mothers in the same year], which means the ratio of aphids remaining the same tree, decreased with increasing in In [stem mother numbers]. Dispersal of progeny of stem mothers as winged females may have a possibility to be a regulatory mechanism for this aphid population. (6) No phenological factors of host tree had significant effect to long term population dynamics of the aphid.

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The author examined the assumption that larvae of cypress bark moth Epinotia granitalis change their feeding sites on host trees of cryptomeria Cryptomeria japonica and avoid the resin flowed from there. Frass and resin flow at the feeding sites indicated that the larvae of E. granitalis scarcely changed their feeding sites and the resin flow of cryptomeria was not active during the period from December to March. But in April and May, the larvae made a lot of new feeding sites and the resin flowed actively out during the period from April to July. These facts suggested that the larvae tend to leave their feeding sites soon after the resin starts flow out, and support the aforementioned presumption.

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