Dynamic patterns of the infestation by the pine needle gall midge, Thecodiplosis japonensis (Diptera: Cecidomyiidae), in endemic regions of Korea.
Percentages of pine needle pairs infested by the pine [Pinus] needle gall midge (PNGM), Thecodiplosis japonensis, were surveyed by the Forestry Research Institute from 1980 to 1997 in the Korea Republic. Data obtained from 32 regions (92 permanent survey sites) surveyed continuously over 15 yr were analysed to determine infestation patterns in spatial and temporal terms. Changes in the percentages of infested pine needle pairs were grouped into 4 types, and there were also characteristic geographical variations. The percentages of infested pine needles were higher than 50% for several years and stabilized after an outbreak in Kyonggi province, while they fluctuated at low levels in Chonbuk, Chonnam, and Kyongnam provinces. PNGM showed infestation changes with an average periodicity of 10-12 yr in endemic regions.