2019 年 22 巻 2 号 p. 31-40
Akiakane (Sympetrum frequens), a Japanese common meadowhawk, is widely distributed in Japan. The larvae hatch in paddy water in a season of rice planting. In recent years in Japan, insecticides for nursery-box application are widely used. As these insecticides include a long-acting type, it is concerned about affecting the growth of S. frequens larvae. The objective of this study is to develop acute toxicity test method for 2nd instar larvae of S. frequens to some typical insecticides for nursery-box application (Fipronil, Imidacloprid) and compare the sensitivity of these insecticides. A 48-hour acute toxicity test method using a 48-well plate was established. Susceptibility to 2nd instar larvae of S. frequens was 48 times higher for fipronil than for imidacloprid. For effective hatching of larvae, it was necessary to treat the eggs at low temperature for at least 4 weeks. The temperature during the acute toxicity test was preferably 21°C. rather than 26°C.
