| Budget Amount *help |
¥2,000,000 (Direct Cost: ¥2,000,000)
Fiscal Year 1987: ¥300,000 (Direct Cost: ¥300,000)
Fiscal Year 1986: ¥1,000,000 (Direct Cost: ¥1,000,000)
Fiscal Year 1985: ¥700,000 (Direct Cost: ¥700,000)
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| Research Abstract |
Integrated mosquito controls using a carnivorous mosquito, Toxorhynchites splendens collected originaly in the Philippines were carried out in a small island, Minnajima, Okinawa Prefecture. At first, observation on the biology and trials of mass production of Tx. splendens under laboratory were carried out to provide base line data for biological control programme. As the result of the observation, the following points were confirmed: In mass production of Tx. splendens, although carnnibalism was observed on the 1st to 3rd days after hatching, the mass rearing method was superior in several points such as small amount of labor and rearing space to the individual rearing method. In 1984 and 1985 a mosquito survey was made in Minnajima and about 11 species were collected. Culex quinguefasciatus and Aedes albopictus were dominant species and target mosquitoes for control. Their main habitats were small containers located around human dwellings and She-oak forest. The mosquitoes were found
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throughout the year, with the greatest peak was found in May and the second peak was in August to September. Field release experiment was also carried out preliminarily and about 900 females and 700 males of Tx. splendens were released 6 times during a period from May to July, 1984. It is confirmed that many larvae of Tx. splendens were found in many containers located in the island. In April 1986, 100 black oviposition containers were placed around dwellings and She-oak forest as monitoring containers for predator and prey larvae, During a period of 3 months from April to August, Tx. plendens were released 6 times totaling 2920 females and 2878 males (average number of about 480 females and males for single release). About 90 % traps were occupied by Tx. splendens larae and a considerable reduction in the number of containers with mosquitoes breeding was observed during that period. However, mosquitoes were increased suddenly one early August, two and half month after last release. In order to make reduce the population of the mosquitoes, the 6th release with 160 females and 150 males of Tx. splendens were made additionally on late August. In 1987, a small number (255 females and 204 males per single release) of Tx. were released 8 times during a long period from April to November. A cosiderable number of Tx. larvae were occupied in the traps and population of target mosquitoes in the traps were reduced significantly throughout the year. Introduction of the guppy, Poecilia reticulata as a biological control agent for small container breeder, Cx. quinquefasciatus and Ae. albopictus in this island was not effective. The effect of methoprene to the target mosquitoes was height, LD50 of methoprene againt the targets was 0.001 ppm at 4th instar larvae. Under desiccate condition, the effect of methoprene applied at 1 ppm in small container lasted for 6 to 8 months. It was useful to control of the small container breeding mosquitoes in this islands. Less
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