In vitro efficacy of plant extracts and bioagents against Pestalotiopsis versicolor, the incitant of leaf spot of guava in Manipur

Efficacy of seven plant extracts was evaluated based on the mycelial growth of the pathogen associated with leaf spot of guava by poisoned food technique. It was found that among the seven plant extracts evaluated, garlic extract @ 2.0 and 4.0% concentrations could inhibit cent per cent growth of pathogen; followed by sweet flag (5 and 10%) to 14.44 and 54.44%, respectively. Derek and periwinkle showed least fungitoxic effect 0.00 and 8.89%, respectively at 5% concentration. Five antagonists viz., Trichoderma viride, T. harzianum, T. hamatum, Penicillium citrinum and P. glabrum were also tested against the pathogen. It was found that bio-control agent T. viride, T. harzianum and T. hamatum came in contact with the pathogen after three days of incubation while T. viride remained locked with the pathogen at the point of contact. T. harzianum and T.hamatum could overgrow 100% on the pathogen. However, the antagonists Penicillium citrinum and P.glabrum could not overgrow the fungus but formed inhibition zones of 0.3 and 1.1 cm, respectively.