Vol. 12, Issue 8 (2023)

Author(s):
GV Suresha, KSVP Chandrika, P Duraimurugan and SJ Rahman

Abstract:
Insect pests constitute major biotic stresses in crop production, inflicting 17.5% yield losses in major field crops. Due to their immediate effects, chemical pesticides have become essential in the management of insect pests. However, increasing environmental concerns, health consciousness, and the demand for organic produce free of residue have necessitated a search for green technology for pest management. However, high dose recommendations, short shelf-life and less persistent nature are major weaknesses of such microbial formulations. Recent research has focused on microencapsulating microorganisms in natural polymers to boost formulation durability and efficacy while lowering dose requirements. The present study was conducted to develop Bacillus thuringiensis var. kurstaki microcapsules by a complex coacervation process and evaluate their effectiveness on a polyphagous pest viz., castor Semilooper (Achaea janata). Pot culture study on castor revealed that the two promising Bacillus thuringiensis var. kurstaki microcapsules viz., CC-1+Btk (Chitosan + lignosulphonate + manganous sulphate + Btk) and CC-2+Btk (Chitosan + lignosulphonate + carboxymethylcellulose + manganous sulphate + Btk) were found effective and recorded higher percent larval mortality (91.66 to 100%) of semilooper (A. janata) as compared to commercial Btk formulations (90.0 to 95.00%). Additionally, the Btk microcapsules showed promising results with a lower percent of active ingredient (a.i.), indicating their potential for use in bio-pesticides. The current study will help to develop eco-friendly and low volume biopolymer formulations of microbial pesticides with increased efficacy and field persistence for effective management of lepidopteran pests.