Fungicides for the Management of Two Newly Emerged Leaf Spot and Blight Diseases of Orchid from Indo-Gangetic Plains of India

Leaf spot (Curvularia geniculata) and blight (Lasiodiplodia theobromae) of orchid are two newly reported diseases in the Indo-Gangetic plains of India. Considering the economic significance of the diseases on the cultivation of orchids, a study was conducted to identify the fungicides which would be effective in management of the diseases. For the study, four fungicides (Metalaxyl 35%WS, Cymoxanil 8% + Mancozeb 64%WP, Azoxystrobin 23SC, Thiophanate Methyl 70%WP) were used at four different concentrations (20 ppm, 30 ppm, 40 ppm, 50 ppm) to assess the percent growth inhibition of the fungi under in vitro condition. Among the fungicides, Metalaxyl 35% WS (40 ppm and 50 ppm) and Cymoxanil 8% + Mancozeb 64%WP (50 ppm) exhibited complete inhibition of fungal growth of Lasiodiplodia theobromae, while Azoxystrobin 23SC (20 ppm) was least effective fungicide. However, Cymoxanil 8% + Mancozeb 64%WP (50 ppm) exhibited 100% growth inhibition at 50ppm against Curvularia geniculata, while minimum inhibition was observed in Thiophanate Methyl 70%WP at all concentrations. Similar study can be conducted under field conditions, so as to further validate the results of our study and establish accurate management strategy for these devastating diseases of orchid.