Two new phytotoxic gamma-lactones, pestalotines A and B (1 and 2, resp.), along with 4-oxo-4H-pyran-3-acetic acid (3) and 6-hydroxyramulosin (=3,4,4a,5,6,7-hexahydro-6,8-dihydroxy-3-methyl-1H-2-benzopyran-1-one; 4), were isolateded from the culture of Pestalotiopsis sp. HC02, a fungus residing in the Chondracris rosee gut. Structures of the new metabolites were elucidated on the basis of their IR, NMR, and MS data. Pestalotines A and B (1 and 2, resp.) significantly inhibited the radical growth of Echinochloa crusgalli with IC(50) values of 1.85 x 10(-4) and 2.50 x 10(-4) M, respectively, comparable to that of 2-(2,4-dichlorophenoxy)acetic acid (0.94 x 10(-4) M) used as a positive control.