2.7.26
INFLUENCE OF SOIL INSECTICIDES ON THE BIOCONTROL POTENTIAL OF TRICHODERMA HARZIANUM

J JAYARAJ, NV RADHARRISHNAN and R RAMABADRAN

Plant Pathology Department, Faculty of Agriculture, Annamalai University, Annamalainagar 608 002, Tamilnadu, India

Background and objectives
The fungal biocontrol agent Trichoderma harzianum is being inoculated for the management of rot diseases of crops in Tamilnadu state. Soil insecticides such as BHC and Phorate that are often applied to soil to control the soil pests, may have definite influence on the growth, activity and biocontrol potential of inoculated population of T. ;harzianum [1]. The present study was taken up to investigate the influence of the above insecticides on the in vitro biocontrol potential of T. ;harzianum and in vivo survival in soil.

Materials and methods
Trichoderma harzianum (TNAU-Strain) was inoculated into Czapek’s medium amended with individual, insecticide (BHC and Phorate) at 5, 10, 50, 100 and 500 p.p.m., to study the in vitro growth, biomass production, sporulation and cellulase production. In vivo studies in soil: The conidial. inoculum of T. ;harzianum was inoculated into garden land soil and the individual herbicide incorporated at 25, 50, 100 and 500 p.p.m. The soil samples were taken at 18-day intervals, up to day 90 and plated in Trichoderma-specific medium and population of the propagules assessed. The competitive saprophytic ability was studied through Cellophane bait method [2].

Results and conclusions
The in vitro sporulation of T. harzianum was drastically inhibited by BHC. Phorate caused the maximum inhibition of in vitro linear growth, biomass production and cellulase production. The inhibition was acute at higher concentrations. Application of Phorate was found to be more inhibitory to the survival and competitive saprophytic ability of T. ;harzianum in soil than that of BHC. The degree of inhibition increased proportionately with the concentration of insecticides.

References
1. Munnecke DE, et al. 1973. Phytopathology 63, 1352-1357.
2. Ahmad JS, Baker R, 1987. Phytopathology 77, 182-189.