Mosquitoes and Their Potential Predators In Rice Agroecosystems of the Mekong Delta, Southern Vietnam

Abstract

Culex tritaeniorhynchus, Cx. gelidus, and Cx. quinquefasciatus, known vectors of Japanese encephalitis (JE), are distributed in rice agroecosystems in Asian countries. Very few integrated studies on the breeding habitats of rice-field mosquitoes, including JE vectors, have been conducted in Vietnam. We investigated the mosquito fauna and potential predators in 8 rice growing areas in the Mekong Delta region of southern Vietnam, during the wet and dry seasons of 2009. Mosquitoes and their predators were collected from a variety of aquatic habitats (rice fields, ponds, wetlands, shrimp ponds, ditches, canals, and rivers). We collected 936 Culex spp. (354 Cx. tritaeniorhynchus, 240 Cx. vishnui s.l., 189 Cx. fuscocephala, and 42 Cx. gelidus), 33 Uranotaenia, 25 Anopheles, and 9 Mimomyia (4 Mi. chamberlaini) in the dry season. During the rainy season, we collected 1,232 Culex spp. (132 Cx. vishnui s.l., 66 Cx. tritaeniorhynchus, 9 Cx. gelidus, 4 Cx. fuscocephala, and 2 Cx. bitaeniorhynchus), 236 Anopheles spp. (40 An. vagus and 1 An. sinensis), and 7 Uranotaenia (3 Ur. lateralis). Heteroptera such as Micronecta, Veliidae, and Pleidae were abundant and widely distributed in both seasons. Based on a stepwise generalized linear model, the abundance of mosquitoes and their predators in rice fields was high when the rice plant length was short and water depth was shallow. Therefore, the use of insecticides during the earlier stages of rice growth should be avoided in order to preserve the predator populations.

Mosquitoes and other aquatic insects in fallow field biotopes and rice paddy fields

“…For the rice fields in August, our analysis suggested that water depth negatively affected mosquito abundance. This finding is similar to those of other studies that have reported mosquito abundance to be negatively related to water depth in rice fields (Ohba et al, 2011) and seasonal pools (Rubbo et al, 2011).…”

Tadpoles of three common anuran species from Thailand do not prey on mosquito larvae

“…In Sri Lanka, egg predation has been observed for the tadpoles of several species; Polypedates cruciger, Bufo melanostictus, Ramanella obscura, Euphlyctis cyanophlyctis , and Hoplabatrachus crassus (Bowatte et al Although some species do prey on mosquito larvae, the great majority of anuran tadpoles are strictly herbivorous. It is often falsely assumed that many tadpoles are mosquito larvae predators (Kumar and Hwang , Raghavendra et al Ohba et al For example, field surveys of available mosquito larvae predators sometimes include tadpoles of unidentified species (Ohba et al More worrisome is the suggestion that tadpoles in general should be considered for the biological control of mosquito larvae, while evidence is based on only a few exceptional species (Kumar and Hwang , Raghavendra et al…”

“…Although some species do prey on mosquito larvae, the great majority of anuran tadpoles are strictly herbivorous. It is often falsely assumed that many tadpoles are mosquito larvae predators (Kumar and Hwang 2006, Raghavendra et al 2008, Ohba et al 2011. For example, field surveys of available mosquito larvae predators sometimes include tadpoles of unidentified species (Ohba et al 2011).…”

“…It is often falsely assumed that many tadpoles are mosquito larvae predators (Kumar and Hwang 2006, Raghavendra et al 2008, Ohba et al 2011. For example, field surveys of available mosquito larvae predators sometimes include tadpoles of unidentified species (Ohba et al 2011). More worrisome is the suggestion that tadpoles in general should be considered for the biological control of mosquito larvae, while evidence is based on only a few exceptional species (Kumar andHwang 2006, Raghavendra et al 2008).…”

Aquatic faunal abundance and diversity in relation to synthetic and natural pesticide applications in rice fields of Central Thailand

“…This corresponds to observations by Leitão et al (2007) who recorded more abundant water bugs near the more open rim zones rather than in the center of the rice fields. Water bugs tend to move off rice fields in the late growing season due to changing requirements or declines of food sources under closing rice canopies (Saijo 2001;Mukai & Ishii 2007;Ohba et al 2011;Phommi 2011). The common corixid bugs (Micronecta sp.)…”