The activities of polygalaturonase and polymethylgalacturonase enzymes were studied on fruits inoculated with L. theobromae along with healthy fruit. The PG activity was higher in fruits inoculated with pathogen than healthy fruits, while no significant difference was observed in PMG activity between inoculated and healthy fruit peel. Generally, enzyme activities showed the rate of maceration of tissues and the extent of rot disease of citrus fruits as well as the aggressiveness and pathogenic abilities of the test pathogens. Biocontrol agents such as Trichoderma sp in the control of Lasiodiplodia theobromae causing stem-end rot of citrus were evaluated in-vitro and in vivo by dual culture technique; to determine their antagonistic effects and find out suitable management strategies. All the antagonists significantly helped in inhibiting the mycelial growth of L. theobromae over control. The results revealed that the selected bio-agents were able to inhibit the growth of the pathogen's mycelial significantly (P = 0.05) after 7 days of incubation. Pseudomonas flourescens showed minimum mycelial growth inhibition (9.44%). Trichoderma sp. also reduces the mycelial extension of the pathogen significantly. In vivo condition, Trichoderma viride (10.87 & 10.43%) was found most potent antagonist in reducing the severity of stem end rot followed by T. virens (13.50 & 12.50 %) in pre- and post-inoculation treatments, respectively after 7 days of inoculation.