Tolerance of fungal and bacterial biocontrol agents to six pesticides commonly used in the control of soil borne plant pathogens

F. A. Mohiddin M. R. Khan

Abstract

The compatability of fungal (Trichoderma harzianum, Trichoderma virens and Pochonia chlamydosporia) and bacterial biocontrol agents (Bacillus subtilis and Pseudomonas fluorescens) was assessed to 6 pesticides viz., carbendazim, mancozeb, metalaxyl, captan, thiram, and nemacur commonly used by farmers in India for the control of soil borne plant pathogens. The compatability was assessed at different concentrations and the concentration of 60, 1050, 160, 225, 25, and 980 µg/ml of carbendazim, metalaxyl, captan, mancozeb, thiram and nemacur was the safe tolerance limit for T. harzianum whereas the corresponding values for T. virens were 40, 1000, 125, 177, 9, and 700 µg/ml, respectively. The safe tolerance limit for P. chlamydosporia were 37.5 µg carbendazim/ml, 75 µg captan/ml, 100 µg metalaxyl/ml, 5 µg thiram/ml, 110 µg mancozeb/ml and 250 µg nemacur/ml. Among the bacteria, P. fluorescens was found to be more compatible with fungicides than B. subtilis and the maximum tolerance concentration for the former being 2500 µg Thiram/ml, 1600 µg mancozeb/ml, and 50,000 µg/ml for captan and carbendazim. Hence, pesticidal contamination at above concentration in soil will not affect their effectiveness. Moreover, the pesticide tolerance ability broadened the use as these biopesticides in conjugation with pesticides can be applied under integrated disease management for the management of soil borne plant pathogens.