Fly ash-based water dispersible powder formulation of Bacillus thuringiensis var. israelensis: Development & laboratory evaluation against mosquito immatures

Abstract

Background & objectives:Bacillus thuringiensis var. israelensis (Bti) formulations are presently being used for insect control. In this study, a water dispersible powder (WDP) formulation using fly ash (FA) as a carrier material was developed and studied for its activity against the larval stages of major mosquito vector species.Methods:An indigenous isolate Bti (Vector Control Research Centre B17) was mass produced using a 100 l fermentor in soya-based medium. The bacterial biomass was mixed with lignite FA and made into WDP formulations. The most effective formulation was used for determining 50 per cent lethal concentration (LC50) against the larval stages of major mosquito vector species, effect on non-target organisms and mammalian systems using standard protocols.Results:Sixteen types of WDP formulations were prepared, of which the formulation containing bacterial biomass, FA and carboxymethyl cellulose was found to be the most effective. The LC50 values of the formulation against Culex quinquefasciatus, Aedes aegypti and Anopheles stephensi larvae were 0.0417, 0.0462 and 0.1091 mg/l, respectively. The formulation was found to be safe to non-target organisms found associated with the mosquito larval stages and also to mammalian systems.Interpretation & conclusions:The study shows that FA can be effectively used to replace commercially available carrier materials used in biopesticidal formulations.

Larvicide Activity of Bacillus Thuringiensis Var. Israelensis. In Simulated Field Condition/ Atividade Larvicida De Bacillus Thuringiensis Var. Israelensis. Em Condição Simulada De Campo

“…aegypti are unlikely to arise resistant to Bti (PÉREZ et al, 2005;SOBERÓN et al, 2018). In addition, these proteins are specific to their target, There are a variety of Bti-based formulations in both liquid and granular form (TAMILSELVAN et al, 2017;SHANKAR et al, 2019), containing crystals with insecticidal activity and viable spores that assist the bacterium's recycling process (BECKER, 2000;MELO-SANTOS et al, 2009). The recycling capacity of Bti can be influenced by environmental conditions, such as: direct exposure to sunlight, ultraviolet radiation and rains that directly affect the efficiency of the biolarvicide (IGNOFFO et al, 1981;PUSZTAI et al, 1991;MYASNIK et al, 2001;ALVES, LECUONA, 1998;MELO-SANTOS et al, 2009;LIMA et al, 2016;ZHANG et al, 2016).…”

Fly ash-based Bacillus thuringiensis israelensis formulation: An ecofriendly approach

“…Indian fly ash has very low radioactivity and heavy metal count 30 . Analysis of the shortlisted formulation by Tamilselvam et al 23 also revealed the presence of only micro- and macronutrients and absence of any kind of heavy metals. This formulation has also shown safety against non-target organisms and mammalian systems.…”

“…Charcoal and plaster of Paris are some of the common carrier material for Bt formulations. Tamilselvam et al 23 in this issue have reported a new carrier material fly ash as an alternative to the common carrier powder-based Bti formulation. Use of fly ash as a carrier in insecticides is generally known.…”

“…Fly ash has earlier been effectively used as carrier in production of biofertilizers and biopesticides 29 . A range of fly ash-based Bti formulations have been evaluated against all three vectors 23 , to arrive at the most effective one. Indian fly ash has very low radioactivity and heavy metal count 30 .…”