Biological Control of Leaf Blight Caused by Alternaria tenuissima (Kunze Ex. Pers.) Wiltshire in Pigeonpea

Three blocontroi agents, Trichoderma viride Kifai, Trichoderma harzlanum Rifal and Gliocladium virens Miller, Gidden and Foster were evaluated against Alternaria tenuissima (Kunze ex. Pers.) Wiltshire, the cause of leaf blight in pre-rabi pigeonpea [Cajanus cajan (L.) Milisp.] in vitro and under field conditions. In dual culture, T. viride overgrew the colony of A. tenuissima within 72 hours of incubation followed by G. virens and T. harzianum, which took more than 96 hours to completely overgrow the colony of test fungus. The radial growth of T. viride was more in mono and dual culture than G. virens and T. harzianum. Microscopic examination revealed that T. viride caused lysis and protoplasmic disintegration of the mycella of A. tenuissima. Under field conditions, two sprays of T. viride @ 4g/l water gave 35.59 per cent control of leaf blight of pigeonpea followed by G. virens which showed 31.32 percent disease control.