BIOEFFICACY OF PHOTORHABDUS LUMINESCENS, A SYMBIOTIC BACTERIUM AGAINST THRIPS PALMI KARNY (THRIPIDAE: THYSANOPTERA)

Abstract

ABSTRACT The primary and secondary forms of Photorhabdus luminescens a symbitotic bacterium of an entomopathogenic nematode Heterorhabditis indica (RCR) was evaluated against Thrips palmi Karny a serious pest on cotton. The treatment included different concentration (101 to 1010 cells/ CFS/ml) of cells and cells free supernatant which was obtained by centrifugation (4000 rpm for 20 min) of broth culture. The treatment was imposed through potter’s tower on aphid colony containing (20 per leaf/replication plants). Observation of aphid mortality was recorded at 24 and 48 hr. The results revealed that both the forms were pathogenic to T. palmi but the cells free supernatant (CFS) of both the forms was more virulent than cells causing high mortality within 24 to 48 hr. The cells of primary and secondary form recorded 67.50 and 72.50 per cent mortality whereas corresponding CFS recorded 85.00 and 80.00 per cent mortality, respectively at the concentration of 1010 cells/ ml. The LC50 of both primary 2.38× 107 cells/ml and secondary form cells 2.35 × 107 cells / ml and CFS of P. luminescens decreased with increase in exposure time from 24 to 48 hr. These results indicate the possibility of developing CFS as a potential biocontrol component against T. palmi.