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Fifty cultivars of rose were screened during 2nd week of April to mid June in year 2015 and 2016 and categorized into six groups i.e. immune, resistant, moderately resistant, moderately susceptible and susceptible to powdery mildew in their reaction. None of rose cultivars was found immune, six cultivars viz. Super Star, Peter Frank Field, Barbara Bush, Monalisa, Raktime and Pink Ice were found resistant and fall in group-2. Eight rose cultivars viz. Sweet Surrender, Heart-O-Gold, Delicia, Phuljhari, Gladiator, Silk Hat, Citrus Tree and Tropical Sunset. In group-4, 24 moderately susceptible cultivars of rose were registered viz. Bride, Sweet Water, Maria Callus, Estrusa, Morning Sun, Honest Red, Summer Fragrance, Red Trumph, Megia Nera, Courage, White Magic, Lynn Anderson, Milky Way, Dr Jo, Olympiad, Excellence, New Zealand, Shah Alam, Paradise, Belles Epoque, Elle,Calico, Flash and World War II. Only twelve cultivars viz. Queen Elizabeth, Peach Beauty, Ashlesha, Deletta, Izume, Machoman, Dance of Joy, Sun Star, Decan Delight, Lutin, Viola and White Weight observed susceptible in group-5 namely. None of the cultivars was found highly susceptible to the powdery mildew. Under greenhouse conditions, eleven cultivars were screened, i.e. High and Yellow, Grand Galla, First Red, Hollywood, High and Peace, Saludo, Konfetti, High and Magic, Upper Class, High and Sparkling and Golden Gate and all were found susceptible to the powdery mildew disease.

Different plants defence activators were evaluated against the rose powdery mildew (Podosphaera pannosa) under green house conditions. Plant defence activators were tested at two concentrations i.e. 0.050 and 0.075% before the appearance of disease. The highest disease control of 78.48% was recorded in the plants sprayed with dipotassium orthophosphate followed by salicylic acid (74.62%), β-aminobutyric acid (72.16%), potassium silicate (64.69%) and potassium bicarbonate (66.79%) at concentration of 0.075% in two consecutive years (2015, 2016). The least disease control (54.95%) was observed in treatment with calcium silicate. At lower concentration (0.05%) disease control was comparatively lesser than the higher concentration of the plant defence activators. First spray of the SAR chemical was effective for 21 days and after that the disease appeared.