MSc

The study entitled “Management of epilachna beetle, Henosepilachna vigintioctopunctata (Fab.) with phylloplane and pathogenic microorganisms” was undertaken in the Department of Agricultural Entomology at College of Agriculture, Vellayani during the period 2013 – 2015 with an objective to manage epilachna beetle in brinjal utilizing phylloplane and pathogenic microorganisms.
Twelve entomopathogenic microorganisms from diseased epilachna grubs and six phylloplane bacteria were isolated. Upon preliminary screening for pathogenicity to epilachna beetle, six bacterial isolates (three from diseased epilachna grubs and three from phylloplane) were found to be infective. The bacteria were identified as Microbacterium sp., Serratia marcescens, Pseudomonas aeruginosa, Pseudomonas fluorescens, C. flaccumfaciens and Bacillus megaterium based on 16s rRNA sequence homology.
The highest chitinase activity was recorded in P. aeruginosa (8.2 units ml-1) followed by B. megaterium (4.8 units ml-1). Chitinase activity was also seen in S. marcescens and P. fluorescens (1.4 and 1.7 units ml-1 each).
In oral and topical exposure studies conducted in the laboratory, S. marcescens produced 93.28 per cent mortality to epilachna grubs at 5 DAT which was statistically on par with that of chemical check (Chlorantraniliprole 18.5 SC). This was followed by P. aeruginosa with a mortality of 73.01 per cent. The phylloplane isolated P. fluorescens and C. flaccumfaciens caused 63.25 and 50 per cent mortality at 7 DAT respectively. Epilachna grubs exposed to S. marcescens caused a leaf area damage of 51.47 per cent as against 100 per cent in untreated check.
In pot culture experiment with foliar application of microbial treatments S. marcescens, P. aeruginosa caused 93.27 per cent and 69.76 per cent mortality in epilachna grubs at 5 DAT and were on par with chemical control (Chlorantraniliprole 18.5 SC). S. marcescens and P. aeruginosa reduced the per plant population of epilachna grubs to 7.54 and 9.86 respectively which was significantly superior to that of untreated check (18.26) and was next best to Chlorantraniliprole 18.5 SC (2.05) at 7 DAT. With respect to all three important parameters, viz. mortality, population reduction and leaf area damage reduction, the treatment with S. marcescens and P. aeruginosa was found to be superior to commercially used fungal entomopathogens like Metarhizium anisopliae, Beauveria bassiana and Lecanicillium lecanii and bacterial entomopathogens like B. thuringiensis and P. fluorescens. The phylloplane isolated P. fluorescens was able to produce mortality of 50 per cent and above at 5 and 7 DAT and could also bring about around 50 per cent reduction in population and more than 70 per cent reduction in leaf area damage over untreated check.
Thus, S. marcescens at a dose of 108 cfu ml-1 is an effective entomopathogenic bacterium in controlling epilachna beetle in brinjal and has a potential to replace chemical insecticides. Since some strains of Serratia marcescens are known to be opportunistic mammalian pathogens suitable bio-safety evaluations have to be conducted before employing it for field level pest management.