[in Japanese]

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[in Japanese]

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Experiments were conducted in 1984 and 1985 in a chestnut orchard in Kumamoto Prefecture where a parasitoid Torymus (Svntomaspis) sinensis introduced from China had been released in 1982, in order to test the effect of two different treatments of pruned twigs on the biological control of the chestnut gall wasp by the imported and native parasitoids. The experimental orchard was divided into two plots, "un-removed" and "removed". All the twigs pruned in the orchard in winter were gathered at the base of each tree in the "un-removed" plot and left there until the parasitoids emerged from withered galls on twigs. The effect of the treatment on the parasitoid effectiveness was not conclusive in the experiment in the first year. In the second year, however, a significantly higher rate of parasitization by a native parasitoid Torvmus (S.) benefcus and the imported T. (S.) sinensis in the "un-removed" plot was achieved than in the "removed" plot. The mortality of host larvae by host-feeding was also significantly higher in the former plot than in the latter. As a result, the mean number of host larvae surviving in a gall was significantly lower in the "un-removed" plot than in the "removed" one. For utilizing native and imported parasitoids more effectively as a biological control method it is suggested that twigs with withered galls pruned in winter should be gathered near the trees and left there until after the overwintering parasitoids emerge from the galls.

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The utilization of Osmia cornifrons (RADOSZKOWSKI) as the pollinator of apples has been achieved successfully for the past 35 years in Aomori and Nagano Prefectures. At present this method is being applied in many Prefectures of Tohoku. On the other hand, in Kyushu the utilization of Osmia bees as pollinators has not been adopted. Attempts were made to utilize Osmia excavata ALFKEN which widely distributed over Fukuoka Prefecture for the pollinating of pears in the Kaho District. A one year experiment conducted in 1986 revealed that the utilization of the bee for such purpose was difficult. Suggestions on the utilization of Osmia excavata as pollinator of pears in Kaho are given in this paper.

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[in Japanese]

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[in Japanese]

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For the purpose of the quantity prediction of the persimmon fruit moth, counting of the numbers of the calyces remained on the twigs after the larvae moved into hibernation sites and those of the hibernating larvae by barking branches was performed. There was a close relationship between the numbers of calyces and those of hibernating larvae. In Kurume District, occurrence of the moth in next spring might be predicted by counting the calyx numbers remained on the trees in winter.

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[in Japanese]

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Laboratory experiments were carried out to analyse the effect of the temperture on the development and prey consumption of Scolothrips sp., a predator of the Kanzawa spider mite, Tetranychus Kanzawai KISHIDA. The developmental period of Scolothrips sp. decreased with the increase of the temperture from 12 to 30°C, and the shortest period of development from larvae to adult was 4.7 days at 30°C. The developmental zero points of larva and pupa were 11.7 and 13.3°C, and total effective tempertures were 56.6 and 32.0 degree days, respectively. The influence of the temperature on the prey consumption of adult Scolothrips sp. was examined using leaf disks. The number of adult female mites and eggs consumed by the adult predator increased with the increase of the temperature from 12 to 30°C. On the average, the predator consumed 7.4 adult females or 36.6 eggs per day at 30°C. The adult female of the predator consumed 10.7 mites or 54 eggs per day at 30°C, however the adult male consumed 4.2 mites or 18.5 eggs per day. It is suggested that the predator is unable to consume the prey at a temperature below 10°C.

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The Japanese cedar bark midge, Resseliella odai sometimes severely hampers timber production of the Japanese cedar, C'ryplomeria japonica mainly in Kyushu. The presence of larvae is associated with fleck marks on the phloem. In some cases cambium layer under the fleck is stained and engulfed in the xylem, and the commercial value of the injured timber is reduced. The occurrence of R. odai and the percentage of injured trees were surveyed in November 1986 at 20 stands of the Japanese cedar plantation in Kagoshima Prefecture. At each stand 50 trees were examined to observe the fleck marks on the phloem, and environmental conditions of the stands were recorded. The bark midge was found at all the 20 stands, and the percentage of injured trees ranged from 4 to 100%. There was a tendency for the percentage to increase at a stand which was characterized by the following combination of growing conditions, location and management: relatively dense stand (over 2, 500 trees/hectare), consisting of younger(shorter and thinner) trees which had not been pruned, located in a valley near a stream, on a slope facing the northeast, north or northwest directions, ground being covered rather densely by low-growing plants. This sort of analysis of environmental conditions is considered to be useful for the control of the bark midge population by modifying the habitat favourable for the bark midge.

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An outbreak of Locusta migratoria L. occurred in September 1986 on Mageshima Island (820ha) which is located 11km west of Tanegashima Island, Kagoshima Prefecture. Since then we have continued to observe the behavior of nymphs and adults on the island at least once a month. Marching, basking and hopper band of nymphs were observed from September to mid-Octorber. A large number of adults swarmed over the island, moving from one place to another and repeating feeding and resting repeatedly, until the end of November. Because we anticipated that the locusts might invade to Tanegashima Island where sugar cane has been extensively cultivated, 3 % fenitrothion dust was sprayed against the nymphs twice in Octorber and against the adults four times from December 1986 to January 1987.

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