Evaluation of plant extracts, bio agents and chemical fungicides against Alternaria solani in Potato under in vitro

Early blight (Alternaria solani) is one of the most important soil and seed borne disease of potato. This disease is very destructive resulting in heavy (20-24%) yield losses. The present investigation was undertaken to develop suitable management strategy against early blight of potato through chemical, bio agents and plant extracts. A study was conducted during kharif season 2016 in the Department of Plant Pathology, College of Horticulture, Bharsar, Uttarakhand. Ten treatments were taken viz; hexaconazole (T1), mancozeb (T2), carbendazim (T3), Trichoderma viride (T4), T. harzianum (T5), Pseudomonas fluorescens (T6), neem leaf extract (T7), garlic extract (T8), onion extract (T9) and T10 (Check) to evaluate their efficacy on early blight disease of potato. The treatments evaluated in vitro conditions were found effective against A. solani and recorded significant radial growth and per cent inhibition of the test pathogen over untreated (control). The results revealed that the minimum radial growth (3.00mm) was observed in T1 (hexaconazole) at 3000 ppm concentration followed by mancozeb (3.16mm), carbendazim (4.36mm), T. harzianum (4.88mm) and neem leaf extract (5.58mm). The maximum radial growth was observed in onion extract (5.75 mm) except check. However, the in vitro per cent inhibition result revealed that the hexaconazole (80.03%) inhibition was observed at 3000 ppm concentration followed by mancozeb (78.97%), carbendazim (70.97%) and T. harzianum (67.53%). Among the all treatments except check, the minimum (61.74%) per cent growth inhibition was observed in onion extract (T9). It can be concluded that hexaconazole is highly effective against Alternaria solani to managing the disease.