author(s)
Abdul Khaliq, Hakim Khan, Maria, Naseem Khan, Laiq Zada, Murad Ali, Muhammad Zahoor and Samiullah

abstract
An in vitro study was conducted to determine the efficacy of Trichoderma harzianum against ten isolates of Alternaria sp, the cause of leaf spot of bitter gourd. Isolates were collected from Peshawar (Chamkani, Nasirpur, Taimulpora, Yaseen Abad and Budhni) and Nowshera (Jabba Daudzai, Zakhi Miana, Ghari Momin, Tarujaba and Qasim Ali Baig) districts during 2011 growing season of the crop. All the ten isolates were cultured in aseptic conditions. Then, an experiment was conducted using Completely Randomized (CR) design. Each isolate was replicated three times. Significant differences (P<0.05) were observed in colony diameter of Alternaria isolates after four and eight days of incubation against T. harzianum. Trichoderma harzianum reduced the mycelia growth of Alternaria isolates by 70.4 to 88.1%, with lowest (70.4%) of Jabba Daudzai and highest (88.1%) of Chamkani as compared with their respective control, when T. harzianum was applied from two sides. It was 76.0 to 92.3% with lowest (76.0%) in Jabba Daudzai and highest (92.3%) of Chamkani, when T. harzianum was applied from four sides to the pathogens as compared to respective control.