The present studies were undertaken to investigate the effect of fungal and bacterial biocontrol agents against stem rot of groundnut. The result of the dual culture technique indicated that Trichoderma isolates inhibited the growth of S. rolfsii. Among the isolate T. viride (Tv1 ) produced maximum reduction of mycelial growth. This was followed by the isolates T. harziaum and T. virens which restricted the mycelial growth when compared to control. Among the isolates T. viride (Tv1 ) at a conc. of 10, 20, 30 and 40 per cent conc. showed an increase in the inhibition of the mycelia growth recording 22.15, 15.27, 8.75 and 0.00 mm respectively. The next best in antagonist was T. harzianum. Among the Pseudomonas fluorescens isolates, PfI3 produced maximum reduction of mycelial growth accounting for 74.97 per cent reduction over control. Also, a general increase in the conc. of the Antagonistic culture filtrate showed an increase in the inhibition of the mycelial growth of the test pathogen.

The present studies were undertaken to investigate the cultural, morphological and pathogenicity characters of Sclerotium rolfsii. Maximum per cent disease incidence was recorded in Nadiyappattu followed by Sivapuri, Kammapuram, Killai, Kurinjipadi, Parangipettai, Chathiram and Puthuchathiram in the decreasing order of merit of Cuddalore district, Tamil Nadu. The native isolates of S. rolfsii were isolated from the respective locations and designated as (SR1 to SR9). All the isolated showed variations with respect to colony character, mycelial growth, no of sclerotia, colour of sclerotia, shape and arrangement of sclerotia. Among the nine isolates of S. rolfsii collected from different groundnut growing areas of Cuddalore district, the isolate (SR5) collected from Nadiyappattu was found to be more virulent and recorded the maximum incidence followed by SR8 collected from Sivapuri. Maximum susceptibility was recorded when the plants are about 45 days showing disease incidence of upto 79.86 per cent.