Persistence of Vectobac WDG and Metoprag S-2G against Aedes aegypti larvae using a semi-field bioassay in Rio de Janeiro, Brazil

Abstract

Persistence of Bacillus thuringiensis var. israelensis (Vectobac WDG) and methoprene (Metoprag S-2G) was evaluated against Aedes aegypti late third instar larvae of the Rockefeller strain in a semi-field bioassay. Tests were performed in Rio de Janeiro, using containers made of plastic, iron, concrete and asbestos, placed in a shaded area. The formulations used were 0.2 g of Vectobac-WDG and 1 g of Metoprag S-2G per 100 liters of water in house storage containers. Vectobac WDG was tested twice, in March and in April/May, 2002. In March (temperature ranging from 21.5 to 39.3 degrees C), 70-100% mortality was observed by the 7th day and declined abruptly thereafter. No significant differences were observed among the container types. In April/May (18.6 to 34.8 degrees C) mortality was higher than 70% to 30-36 days in all cases, except in the iron container (40% mortality on the 12th day). Metoprag S-2G was evaluated in April/May, 2002, and induced mortality higher than 70% up to 15 days in the plastic and iron containers and only seven days in the concrete container. In the asbestos container, maximal mortality was achieved on day one post-treatment (66%). Our results point to a low persistence of both formulations in the weather conditions of Rio de Janeiro.

Evaluation of a new formulation of Bacillus thuringiensis israelensis

“…Studies to understand the lethal action of commercial or new formulations of bio-insecticides with Bti-based active principles are conducted regularly (Ibarra et al, 2003;Praça et al, 2004;Lima et al, 2005;Osborn et al, 2007). However, the target-species in experiments vary according to the mosquito species of major health concern in each region.…”

Chitin synthesis inhibitor effect on Aedes aegypti populations susceptible and resistant to organophosphate temephos

“…In Brazil, only the OP and, later, Bti have been employed in this context33 (a timid attempt to use methoprene was not further pursued). However, temephos resistance of mosquito populations was detected,10–12 as well as a low persistence of the Bti and methoprene formulations available to the Brazilian Dengue Control Programme 14, 15…”

“…aegypt i 11. However, the low residual effect of Bti formulations available to the Brazilian Dengue Control Programme14, 15 showed the need for novel formulations or larvicides.…”

Impact of insecticide interventions on the abundance and resistance profile of Aedes aegypti

“…We evaluated four forms of vector control : (1) larval control [12,43], (2) adult control using ultra-lowvolume insecticide applications [15,16], (3) adult control using insecticide treatment of surfaces and materials [20,21], and (4) adult control using lethal ovitraps [22] ( [4,[14][15][16]. Adult control using ultra-low-volume insecticide applications are carried out during the dengue season : evaluated interventions ranged from 1-12 applications per dengue season.…”