Insecticide susceptibilities of Hydrometra species (Hemiptera: Hydrometridae), including an endangered species, inhabiti
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ORIGINAL RESEARCH PAPER
Insecticide susceptibilities of Hydrometra species (Hemiptera: Hydrometridae), including an endangered species, inhabiting paddy fields in Japan Kouhei Murata1 · Koichi Tanaka2 Received: 2 March 2020 / Accepted: 26 July 2020 © The Japanese Society of Applied Entomology and Zoology 2020
Abstract Freshwater ecosystems tend to have the highest proportion of species threatened with extinction. Paddy fields provide alternative habitats for many species inhabiting wet hinterlands of rivers. This study examined the susceptibilities of three hydrometrid species, Hydrometra procera Horváth (Hemiptera: Hydrometridae), H. albolineata (Scott) (Hemiptera: Hydrometridae), and H. okinawana Drake (Hemiptera: Hydrometridae), inhabiting paddy fields in Japan to seven insecticides that were frequently applied to paddy fields, and evaluated the effect of each insecticide according to the hazard assessment classes by the International Organization for Biological Control and Integrated Control of Noxious Animals and Plants/ West Palearctic Regional Section. Etofenprox, imidacloprid, and fenobucarb were found to be seriously harmful to the third instar nymphs of the three hydrometrid species. Buprofezin (an insect growth regulator) was also evaluated as seriously harmful based on the mortality at the third instar of the three species before the completion of molting to the fourth instar. Etofenprox, imidacloprid, and buprofezin were particularly harmful even at low concentrations to H. procera. Some of these insecticides have been heavily used in paddy fields since the 1950s or 1960s. It was around this time when the endangered species, H. albolineata populations began to decline drastically. Our results suggested that heavy use of these insecticides is one of the factors that caused the decline in H. albolineata populations. Keywords Harmful pesticide · Hazard assessment · Predator · Semi-aquatic bug · Vulnerable species
Introduction Freshwater ecosystems tend to have the highest proportion of species threatened with extinction (Millennium Ecosystem Assessment 2005). In agro-ecosystems, rapid and intensive urbanization along with agricultural development has led to the environmental deterioration and loss of freshwater habitats, resulting in a significant decline in many populations of freshwater species (Allan and Flecker 1993). Rice paddy ecosystems serve as important habitats for freshwater and wetland animals and plants. In Japan, rice paddy fields * Kouhei Murata [email protected]‑tokai.ac.jp 1
Department of Plant Science, School of Agriculture, Tokai University, Toroku, Kumamoto 862‑8652, Japan
Laboratory of Entomology, Department of Bioresource Development, Tokyo University of Agriculture, Atsugi, Kanagawa 243‑0034, Japan
2
have provided alternative habitats for many species inhabiting wet hinterlands of rivers (Kiritani 2000; Moriyama 1997). For example, a huge number of insect species have been recorded in rice paddy fields (Kiritani 2010; Kobayashi et al. 1973; Yano 2002). However, recent agr
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