Nature First
The MCGM plans to develop the biolarvicidal VectoBac 12AS that is used in mosquito control, the eco-friendly way with natural plant extracts. Irene Fernandes brings you the details ……..Irene Fernandes
In an effort to keep to the environment as safe as possible using miniamal amounts of toxins, the Municipal Corporation of Greater Mumbai (MCGM) has been using bio-friendly larvaecidals to control the spread of mosquito larvae and other vector-borne diseases in the city.
Around one and a half years back, the MCGM experimented with the bactericidal VectoBac 12 AS, that makes use of bacteria Bacillus thuringiensis israelensis (Bti), which acts directly on the mosquito larvae. Bti was found bring about least harm to the environment and has shown effective results so far, as told by the municipal authorities. For this reason, the authorities plan to develop the larvicidal further by incorporating natural plant extracts.
“The results shown after the usage of VectoBac 12 AS (the commercial name for Bti) is commendable. We have a reduced number of mosquito-related diseases such as dengue and malaria,” informs Dipak Adsul, insecticide officer of MCGM. Adsul also briefs TSM about the constant surveys that are being conducted for at least four times a year to control mosquito breeding as far as possible.
The MCGM had been using larvicides containing organic chemical extracts like pyrethrum and nicotine since years but their effects were seen on other species too besides mosquitoes. Hence, the MCGM has taken serious steps to rectify this problem. One step towards this was to maintain the target specificity affecting least number of species in the environment.
Adsul explains the mode of action of Bti and its choice for mosquito larvaecidal compared to the rest. He says that Bti products when ingested by the larval stage of the mosquito is known to cause its mortality. Following ingestion, in the alkaline larval midgut, the soluble insecticidal crystal proteins resulting in pore formation in the midgut, which leads to death of the larva. Apart from this, Bti has several other advantages that favour the environnment and most of its species (see box to the left).
Keeping the target specificity in mind, the trial experimentations on Bti were suceesfully conducted. Presently, Bti is used in its liquid form and is sprayed using the thermal fogging machines. Its powdered form has operational issues hence, its redundant use. Now, the MCGM plans to make bti asthetically appealing for public use as well. They plan to introduce the tablet form of Bti.
“The efficacy of Bti’s in the liquid form has been successful though the general reaction of the public is that of inconvenience. Therefore, we are planning to develop the tablet form of Bti. The tablet form will aim to control the mosquito’s life-cycle growth. Development processes are still in the pipeline,” explains Adsul. Further plans of developing VectoBac 12 AS will include the substitution of natural extracts as mosquito repellants as a part of the larvicidal, explains Adsul.
irene.fernandes@timesgroup.com
Environmental and health impacts of Bacillus thuringiensis israelensis (Bti)
* Bti has been reported to affect a fewer number of other invertebrate species including most aquatic fauna.
* Bti is considered to pose little threat to mammalian safety.
* Bti does not persist in the environment after application. Generally, reports of activity after application show a decline in efficacy within days and little residual activity after several weeks.
* The persistence of Bti after application is dependent on the type of formulation/product used, with some formulations designed specifically to enhance residual activity.