Abai, MR

6th International Congress of DipterologyEffects of early abscission of galled organs on populationdynamics of gall midge species (Diptera: Cecidomyiidae)Yukawa, J. (1), K. Nakagawa (2), A. Kono (3), T. Maki (4), T. Sadoshima (5), T.Yamaguchi (6) & T. Satonaka (7)(1) Kyushu University, Hakozaki, Fukuoka 812-8581, Japan(2) Kawanabe Agricultural Improvement and Advisory Center, Kagoshima Prefecture,Minami-Satsuma 897-1121, Japan(3) Aira Agricultural Improvement and Advisory Center, Kagoshima Prefecture, Kajiki899-5212, Japan(4) Sankei Chemical Co., Ltd., Higashi-Ueno, Tokyo 110-0015, Japan(5) Fukuoka Sub-Station, Moji Plant Protection Station, Fukuoka 812-0031, Japan(6) National Agricultural Research Center, Tsukuba, Ibaraki 305-8666, Japan(7) Nagasaki Agricultural and Forestry Experiment Station, Isahaya 854-0063, JapanIn order to find regulation mechanisms of gall midge population density,we have been studying, since 1970, population dynamics of severalunivoltine gall midge species (Diptera: Cecidomyiidae) that inhabit forestsof broad-leaved evergreen trees in southern parts of Japan. In various gallmidge–host plant systems, we observed that early abscission of galledorgans affected gall midge populations density-dependently in some casesand density-independently in other cases. The longevity of heavily galledleaves was shortened in the systems of Pseudasphondylia neolitseae–Neolitsea sericea (Lauraceae), Illiciomyia yukawai–Illicium anisatum(Illiciaceae), and Masakimyia pustulae–Euonymus japonicus(Celastraceae). Such an earlier drop of galled leaves operated as a densitydependentmortality factor on the gall midge populations. In contrast,heavily galled leaves did not drop earlier than ungalled leaves in thesystems of Daphnephila machilicola–Machilus thunbergii (Lauraceae) andLasioptera camelliae–Camellia japonica (Theaceae) because of toughnessof the host leaves. Some galled and ungalled leaves of Elaeocarpussylvestris (Elaeocarpaceae) naturally drop to the ground a little before theemergence season of Pseudasphondylia elaeocarpini, which causes thedeath of the gall midge when the fall of galled leaves occurred beforepupation. In the system of Asphondylia sphaera–Ligustrum japonicum(Oleaceae), abortion of flower buds and young fruit caused the death of the325