Author(s): Ashwini M, Rajkumar Kothikar and Mina Koche

Abstract: The rose leaves showing typical symptoms of black spot were collected from Horticulture Field, College of Agriculture, Nagpur and used for isolation of pathogen on potato dextrose agar media. The culture of the pathogen was examined for morphological and cultural characteristics. On the basis of hyphae, shape of spore produced, colour and type of colony, the fungus was identified as Diplocarpon rosae and it proved the Koch’s postulates. The fungicides viz., Azoxystrobin (Amistra), Mancozeb+Carbendazim (Bendaco), Thiophenate methyl (Topsin-M), Mycobutanil (Systhane), Tebuconazole (Folicure), Chlorothalonil (Daconil) and control were evaluated against Diplocarpon rosae. Results revealed that, after third spray, minimum per cent disease intensity was recorded by chlorothalonil 0.2 per cent (11.23 PDI) and topsin M 0.05 per cent (13.50 PDI) and both these treatments were at par with each other. Next promising treatment was myclobutanil (0.1%) followed by mancozeb+carbendazim (0.2%), azoxystrobin (0.1%), T. viride (0.2%) and tebuconazole (0.1%) recording 15.32, 18.13, 21.10, 25.24, 30.27 PDI respectively. Maximum cut flower yield was obtained in the treatment chlorothalonil (19.55 q ha^-1) and the per cent increase in the yield over control was 67.32 per cent followed by topsin M, myclobutanil, mancozeb+carbendazim, azoxystrobin, T. viride and tebuconazole with 55.05, 35.25, 27.40, 19.54, 14.20, 10.52 per cent increase in the yield over control, respectively. In case of ICBR, the most economical treatment was topsin M recorded ICBR of 1:22.57. This was followed by chlorothalonil, myclobutanil, mancozeb+carbendazim, T. viride and tebuconazole recorded 1:10.55, 1:6.96, 1:8.19, 1:4.62 and 1:1.40 ICBR respectively. The least ICBR was found with azoxystrobin recording 1:1.28 due to high market price of the fungicide.

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