Larvicidal Activity of Bacillus laterosporus Against Mosquitoes

In present study Bacillus laterosporus isolated from a commercial formulation showed larvicidal activity against second instar larvae of Aedies aegypti, Anophles stephense and Culex qunquefasciatus. The % mortality without heat treatment was 37.34 against Anophles and 18.67 against Culex. The toxin was heat stable and its toxicity increased with inoculum size and incubation time. The study reveals that this strain of B. laterosporus has limited potential as an agent for mosquito vector control. The use of entomopathogenic bacteria like Bacillus sp., Pseudomonas sp., Serratia sp. and Yersinia entomophaga is a viable safe alternative for pest control that can reduce ecological damage caused by the use of chemical insecticides (De Oliveira et al., 2004; Charles et al., 1996; Gonzalez et al., 2013). Among these microbes B. laterosporus is new and its toxicity against the larvae of mosquitoes Aedes aegypti, Anopheles stephensi, and Culex pipiens has been reported by Favret and Yousten (1985). The B. thuringiensis is more efficient larvicidal strain than other bacillis species like B. sphaericus and other (Jahan and Hussain, 2011). It was reported that toxicity level of Bacillus laterosporus was though lesser than that of B. thuringiensis had higher insecticidal activity at stationary phase or at sporulated cultures against Ae. aegypti and An. stephensi larvae (Rivers et al., 1991; Ruiu et al., 2007; Orlova et al., 1998). B. laterosporus exhibits nonpathogenic effects towards non-target species (Ruiu et al., 2013). B. laterosporus a spore-forming bacterium characterized by its ability to produce a canoe-shaped parasporal inclusion adjacent to the spore, has been isolated from a wide range of materials including soil (De Oliveira et al., 2004), insect bodies (Smirnova et al., 1993), leaf surfaces (Sarkar et al., 2002), compost (Adegunloye et al., 2007), honey (Iurlina and Fritz, 2005), starchy foods (Fangio et al., 2010), olive mill wastewater (Aguilera et al., 2001) and fresh water (Laubach, 1916). Some strains of B. laterosporus exhibit antimicrobial activity against bacteria and fungi and have ______________________________ * Corresponding author: [email protected] 0030-9923/2016/0001-0281 $ 8.00/0 Copyright 2016 Zoological Society of Pakistan been used in medicines (Umezawa and Takeuchi, 1986). B. laterosporus is used as probiotics for mammals and birds (Hong et al., 2005; Duc et al., 2004). It has application for the treatment of soil to improve soil properties like maintenance of an alkaline pH, fixation of nutrients, neutralization of odors and to improve the microbial status of soil (Canbolat et al., 2006; O'donnell, 1997). Though B. laterosporus strains are ecofriendly, they are rarely reported for their use in bioremediation. It has potential for azo dye decolorization and successfully used for the treatment of different textile wastewater (Kurade et al., 2013; Gomare and Govindwar, 2009). In present study B. laterosporus was isolated from a commercial formulation that is being applied as microbial soil conditioner. They can upgrade the supply level of nutrients substances in soil and improve its physical and chemical properties. Soil conditioner gives higher yield when applied to crops and reduce the dosage of fertilizer (Guangdong Detection Centre of Microbiology, China). As reported in literature (Favret and Yousten, 1985; Ruiu et al., 2007) some species of B. laterosporus have larvicidal activities against mosquitoes larvae. Present study examines the larvicidal activity of B. laterosporus against second instar larvae of Ae. aegypti, An. stephensi and Cx. pipiens. Materials and methods In an Erlenmeyer flask one gram of the sachet material (UNIGROW, Soil Conditioner By Winnerway, P.O. Box 523070, Guangdong, P.R.C) was suspended in 100 mL autoclaved distilled water, shaken for one hour Article Information Received 12 March 2015 Revised 17 August 2015 Accepted 20 August 2015 Available online 1 January 2016 Authors’ Contributions FB performed bioassays, analyzed the data and wrote the article. SA and RS isolated and characterized the bacteria. RAK provided research facilities as Principal Investigator.