STUDIES ON EFFICACY OF NATIVE ISOLATES OF Metarhizium anisopliae Metchinkoff SOROKIN AND ITS SECONDARY METABOLITE DESTRUXIN AGAINST TOBACCO CATERPILLAR Spodoptera litura Fab EPIDOPTERA NOCTUIDAE

Abstract

newline Investigation on the effectiveness of native isolates of Metarhizium anisopliae and its newlinesecondary metabolite, destruxin was tested against tobacco caterpillar, Spodoptera litura newline(Fab.) (Lepidoptera: Noctuidae), at ICAR-AICRP on Biocontrol, Main Agricultural Research newlineStation, University of Agricultural Sciences, Raichur, between 2021 and 2023. Pathogenicity newlinestudies involving 12 native isolates of M. anisopliae revealed that UASR BC-Ma38 as the newlinemost potent, causing 98.89 per cent mortality, followed by UASR BC-Ma35, ICAR-NBAIRMa4 and UASR BC-Ma60. Apart from that UASR BC-Ma38 recorded highest activity of newlinechitinase (8.497 ± 0.177 and#956;mole/mL/min), protease (61025 ± 1270.34 RFUs) and lipase newline(10.238 ± 0.26 and#956;mole/mL/min) activity with 28 volatile bioactive compounds and secondary newlinemetabololite destruxin A (dxt A) concentration of 80.01 ± 1.67 mg/L. In contrast, ICARNBAIR-Ma14 displayed lower mortality (45.56 %) and less cuticle degrading enzyme newlineactivity and destruxin A concentration of 1.63 ± 0.03 mg/L. The potent isolate, UASR BCMa38, further utilized for development of novel formulations for its storability and newlineeffectiveness. Microencapsulation with sodium alginate, gelatin and calcium chloride resulted newlinein particles size of 6.5 to 7.0 microns, while gel formulation is spherical beads with 4 mm newlinediameter. The efficacy studies revealed that microencapsulation formulation found to be newlinesuperior over the alginate gel formulation over six months of storage at 4 oC and 25 oC, newlinewhile the alginate gel formulation remained effective only for two months. In conclusion, newlineUASR BC-Ma38, a highly virulent isolate, stands out due to its elevated cuticle degrading newlineenzyme activity and significant destruxin A concentration and suggests its potential as a newlinegreen insecticide for eco-friendly pest management. newlineKey Words: Metarhizium, Spodoptera, Microencapsulation, gel and destruxin A