Combined effect of Leptolegnia chapmanii (Oomycota: Peronosporomycetes), Bacillus thuringiensis var. israelensis and temephos on the mortality of Aedes aegypti larvae

PELIZZA SEBASTIAN ALBERTO; LÓPEZ LASTRA C.C; LAINO C. C; SANTOS M. E; PANISSE G; GARCÍA JUAN JÓSE

Brasília-DF. Brasil

Simposio; X Simpósio de Controle Biológico (Sicombiol); 2007

Embrapa Brasil

As populations of pesticide-resistant mosquitoes increases and concerns related to theuse of pesticides in aquatic environments grows, alternatives such as natural control and integrated control methods are being investigated. Aedes aegypti (L) is the primary vector of dengue virus in the Americas including Argentina. The goal of this study was to evaluate the combined effect of three larvicides, Temephos 50% (BASF), a liquid formulation of Bacillus thuringiensis var. israelensis (Bti BIAGRO, Laboratorio BIAGRO, Argentina) and zoospore suspensions of an Argentinean isolate of the mosquito pathogen Leptolegnia chapmanii Seymour (Oomycota: Peronosporomycetes). Twenty five 4th instar Ae. aegypti (L.) larvae were placed in plastic containers with 150 ml of dechlorinated water and the following combinations and concentrations of the three larvicides tested were added to each container: 1) 94,000 zoospores de L. chapmanii; 2)Temephos 0.00035ppm; 3)Temephos 0.001ppm; 4) Bti 0.012ppm; 5)Bti 0.027ppm; 6)Temephos 0.00035 ppm + 94,000 zoospores; 7)Temephos 0.001ppm + 94,000 zoospores; 8)Bti 0.012ppm + 94,000 zoospores; 9)Bti 0.027ppm + 94,000 zoospores; 10)Bti 0.012ppm + Temephos 0.00035ppm; 11) Bti 0.027ppm + Temephos 0.001ppm; 12)Bti 0.012ppm + Temephos 0.00035ppm + 94,000 zoospores 13)Bti 0.027ppm + Temephos 0.001ppm + 94,000 zoospores. Three containers for each combination and three controls treated in the same manner without the addition of larvicides were used in this test. Three repetitions of this assay were conducted in different dates. Treated and control containers were maintained at 25±1ºC and 12:12(L:D) photoperiod. Larvae mortality rates were recorded at 48 h post-treatment and results for each larvicides combination were: 1)44.6%; 2)59.3%; 3)97.3%; 4)33.3%; 5)61.3%; 6)89.3%; 7)100%; 8)80%; 9)90.6%; 10)100%; 11)100%; 12)100% y 13)100%, respectively. Results clearly showed that use of L. chapmanii is compatible with the two most commonly used larvicides in mosquito control programmes around the World, such as Bti and Temephos. It was also observed an increase in the larvae mortality rates when these larvicides were combined with L. chapmanii zoospores. Apoio financeiro: ANPCyT PAedes aegypti (L) is the primary vector of dengue virus in the Americas including Argentina. The goal of this study was to evaluate the combined effect of three larvicides, Temephos 50% (BASF), a liquid formulation of Bacillus thuringiensis var. israelensis (Bti BIAGRO, Laboratorio BIAGRO, Argentina) and zoospore suspensions of an Argentinean isolate of the mosquito pathogen Leptolegnia chapmanii Seymour (Oomycota: Peronosporomycetes). Twenty five 4th instar Ae. aegypti (L.) larvae were placed in plastic containers with 150 ml of dechlorinated water and the following combinations and concentrations of the three larvicides tested were added to each container: 1) 94,000 zoospores de L. chapmanii; 2)Temephos 0.00035ppm; 3)Temephos 0.001ppm; 4) Bti 0.012ppm; 5)Bti 0.027ppm; 6)Temephos 0.00035 ppm + 94,000 zoospores; 7)Temephos 0.001ppm + 94,000 zoospores; 8)Bti 0.012ppm + 94,000 zoospores; 9)Bti 0.027ppm + 94,000 zoospores; 10)Bti 0.012ppm + Temephos 0.00035ppm; 11) Bti 0.027ppm + Temephos 0.001ppm; 12)Bti 0.012ppm + Temephos 0.00035ppm + 94,000 zoospores 13)Bti 0.027ppm + Temephos 0.001ppm + 94,000 zoospores. Three containers for each combination and three controls treated in the same manner without the addition of larvicides were used in this test. Three repetitions of this assay were conducted in different dates. Treated and control containers were maintained at 25±1ºC and 12:12(L:D) photoperiod. Larvae mortality rates were recorded at 48 h post-treatment and results for each larvicides combination were: 1)44.6%; 2)59.3%; 3)97.3%; 4)33.3%; 5)61.3%; 6)89.3%; 7)100%; 8)80%; 9)90.6%; 10)100%; 11)100%; 12)100% y 13)100%, respectively. Results clearly showed that use of L. chapmanii is compatible with the two most commonly used larvicides in mosquito control programmes around the World, such as Bti and Temephos. It was also observed an increase in the larvae mortality rates when these larvicides were combined with L. chapmanii zoospores. Apoio financeiro: ANPCyT P