Comparative field efficacy of various entomopathogenic fungi against Thrips tabaci: prospects for organic production of onion in India

India ranks first in world in export of Allium cepa. The crop production is subjected to stress by the sap sucking pest, Thrips tabaci. There is an increasing demand for alternative non-toxic and eco-friendly management strategies such as biological control of horticultural crop pests in the recent years, due to the varied disease effects of pesticides. Preliminary studies at our institute indicated fungal pathogens isolated from thrips (institute isolates) as potential biological control agents of T. tabaci in onion. This paper reports on the field efficacy of these microbial control agents against Thrips tabaci in onion cultivar ‘Arka Niketan’ at the Indian Institute of Horticultural Research, Bangalore, India. Four species of microbial pathogens (Metarrhizium anisopliae, Verticillium lecanii, Beauveria bassiana and entomophilic nematode Steinernerma casrpocapsae; Bouncer) at different dosages (1×10(9) and 1×10(7) spores/ml) were evaluated. Two criteria i.e., thrips density and marketable yield were selected to determine the effectiveness. Thrips density/plant was estimated through a destructive sampling method and yield gain by recording marketable produce that was subjected to t-test to determine the best treatment. Results indicated significant reduction in thrips population/plant and corresponding yield increase in entomopathogen treatments that was on par to chemicals. A mean population of 8.3 to 10.0 thrips/plant was recorded in entomopathogen treatments compared to 18.4 in control and 5.5 thrips/plant in chemical check respectively. M. ansiopliae at a concentration of 1×10(9) spores/ml with adjuvant (sunflower and Triton-X) recorded the lowest thrips/plant population contributing to 58% reduction and 49.12% increase in yield over control. This study suggests that entomopathogens can substitute chemical pesticides in the management of Thrips tabaci in onion.