The antifungal activity of Gracilaria cervicornis, Gracilaria gracilis, Endocladia muricata is tested against Macrophomina phaseolina and Lasiodiplodia theobromae. The mean inhibion zones induced by seaweed extracts on the tested pathogens revealed that methanolic extract of G. cervicornis had highest zone than its acetone & aquous extracts followed by methanoilc extract of G. gracilis against M. phaseolina whereas no inhibition by E. muricata. The methanolic extract of G. cervicornis recorded inhibition zone of mm against M. phaseolina whereas in L. theobromae it was mm. But the acetone extract of G. gracilis showed mm against M. phaseolina whereas it was mm for G. cervicornis. | GC-MS analysis of bioactive compounds of seaweed extracts collected from seashore of Manalmelkudi (Pudukkottai dist., Tamilnadu), responsible for antifungal activity