Preliminary assessment of Phoma herbarum as a potential mycoherbicide against Hyptis suaveolens.
A mycopathological survey was conducted that yielded an isolate of Phoma herbarum [Phoma exigua var. exigua] inciting severe infection and responsible for natural epiphytotics in weed (Hyptis suaveolens) seedlings. Diseased parts of H. suaveolens were collected during an extensive survey conducted in and around Jabalpur region, Madhya Pradesh, India. Three strains of P. herbarum were obtained from various parts of the target weed. Out of these, FGCC#70 strain incited severe infection and proved to be highly pathogenic to host. Large-scale epiphytotics of the pathogen was also observed in the natural condition. The disease initially started from the middle part of the lamina as small, discoloured spots. Later on, spots became circular to irregular, light brown, surrounded by reddish brown hollow. When the humid weather prevailed, the spots coalesced and formed larger spots. The incidence was as high as 90%. Treated seedlings initially showed yellowing and turned blackish at advanced stages and more than 90% seedlings were killed by the fungus (FGCC#70). Abundant colonization and pycnidia formation were observed on seeds and inflorescence. The pathogen was reisolated from inoculated parts, which clearly indicated that the present strain FGCC#70 had tremendous mycoherbicidal potential against H. suaveolens.