• Journal of Korean Society of Forest Science
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• v.87 no.3
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• pp.475-482
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• 1998

9 species of parasitoids emerged from chestnut gall samples collected at Chunchon, Kangwon in June to July 1995 - 1997, and 8 species emerged from gall samples at the 5 investigation sites in December 1997. The primary parasitoids among them were Torymus sinensis, Torymus geranii, Sycophila variegata, Megastigmus nipponicus, Megastigmus maculipennis, Eurytoma brunniventris, Ormyrus flavitibialis, Ormyrus punctiger, Eupelmus urozonus, while the secondary parasitoids were Torymus geranii, Sycophila variegata, Eupelmus urozonus, Eupelmus sp., Eurytoma setigera, Ormyrus punctiger. Torymus sp.. Some of secondary parasitoids were facultative hyperparasitoids, parasitizing the gall wasp as well as primary parasitoids, Among these natural enemies, Torymus sinensis was dominant at all sites. At Chunchon, the rate of gall formation showed decreasing tendency as the function of generation and the parasitism rate of Torymus sinensis showed increasing tendency gradually. But the rate of parasitization of the secondary parasitoids(Sycophila variegata, Eupelmus urozonus, Torymus geranii, Ormyrus puntiger) ranged from 4.0% to 10.5%. The mortality was high during June to October which was immature stage of Torymus sinensis, and mainly caused by secondary parasitoids. Torymus sinensis emerged from April to May and the estimated dates of 50% emergence was 21st April. The estimated dates of 50% emergence for the other, Sycophila variegata, Eupelmus urozonus, Torymus geranii, and Ormyrus puntiger were 25th April, 30th April, 4th May, and 22nd May, respectively.

• Journal of Korean Society of Forest Science
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• v.77 no.4
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• pp.382-388
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• 1988

Improvement of productivity by forest tree breeding work in Korea was estimated for a few important tree species. Progenies of 17 plus trees of red pine (Pines densiflora) outgrew by 57 percentage compared with progenies of unselected trees at age 15. If best three families are selected among the 17, more than double in volume grow-th is expected. The hybrid Pinus rigida ${\times}$ P. taeda showed more than double volume growth compare to P. rigida at a southern plantation at age 15. However, the superiority of the hybrid decreased at northern plantations, mainly because of low coldhardiness of the hybrid. At a northern plantation, the hybrid grew less than the P. rigida on upper hill, while the hybrid grew much better than the P. rigida on flat area. Another hybrid Populus alba ${\times}$ P. glandulosa grew faster than both parents by two to two and half times according to planting sites at age 10. Introduction of Pinus rigida also showed increased volume growth. Volume increase by selection of best five provenances among 45 at age 12 was estimated as 53 percent compare to progenies of plus trees in Korea, Additional 19 percent of volume increase was expected by selection of the best families within the best provenances. Annual production of chestnuts reached about 70,000 M/T by planting resistant clones to chestnut gall wasp (Dryocosmus kuriphilus), which killed almost all susceptible trees. Although polyploid trees and mutants have been produced by colchicine treatments in over 10 tree species, none of them is economically important Remarkable improvement of productivity is expected by biotechnology in future through selection, hybridization, introduction of foreign genes at cell, cell organelle and gene level, and gene transformation. At present, mass propagation of superior planting materials by tissue culture will increase the productivity.