Bioefficacy of Fungicides, Bio-Control Agents Leaf Spot of Potato Incited by Alternaria solani

Efficacy of eight fungicides with three different concentrations, that is, 500 and 1000 ppm were studied in vitro against Alternaria solani by poisoned food technique. Results revealed that Iprodione was significantly superior to all other fungicides by inhibiting (100%) growth followed by Mancozeb (90.28%) and Carbendazim (88.18%) over control after 10 days of incubation. Biocontrol agent namely, Trichoderma viride, Gliocladium spp., Trichoderma harzianum, Trichoderma koningii and Pseudomonas fluorescens were evaluated for their efficacy against A. solani in vitro. Percent inhibition of the test pathogen ranged from 45.16 to 75.67%. T. harzianum, was found to be the most effective antagonist which caused growth inhibition of 75.57%, followed by T. viride (64.28%). It showed the possibility of the most ecofriendly and inexpensive method of control of the early blight disease. A total of thirteen plant extracts which were locally available were evaluated in vitro against A. solani and were tested applying poisoned food technique. Overall percent inhibition of growth of the fungus ranged from 16.05 to 80.46%. Azardicata indica recorded maximum average inhibition of 80.46 per cent followed by P. longifolia with 77.76% and O. sanctum 71.41%. Whereas, Parthenium hysterophorus showed minimum mean inhibition of 16.05%, respectively. The results from field experiment revealed that the percentage reduction in Early leaf spot incidence over untreated control (00.00%) revealed that fungicide, iprodione caused highest reduction (67.04%) in the disease incidence. This was followed by mancozeb (59.43), SAFF (53.37%) and chlorothalonil (51.14%). Less than 50% reduction in disease incidence was recorded with carbendazim (47.48%) followed by hexaconazole (42.29%), tebuconazole (41.47), bioagent T. harzianum (35.03%) and botanical A. indica (32.39%). Botanical Z. officinale and bioagent P. fluorescens were found less effective both of which recorded significantly least reduction (28.24) in blight incidence. Highest tuber yield recorded on fungicide Iprodione with (350.26q/ha) and over unsprayed control (yield, 150.20 q/ha) with significantly least mean Alternaria blight incidence (16.16%) and intensity (21.96%). The second and third best fungicides found were mancozeb (@ 0.2%) and SAFF (0.25%) which recorded tuber yield, respectively of 300.61 q/ha and 288.61q/ha.