It is most severe after long wet, warm periods in the spring. The fungus Diplocarpon rosae causes black spot disease. Williams Fountain, University of Kentucky, īlack spot is a common and serious rose disease often reaching epidemic proportions in a season. Plant Disease 103:1577-1583.Black spot (caused by Diplocarpon rosae) of rose. Characterization of Botrytis cinerea From Commercial Cut Flower Roses. Reference Muñoz, M., Faust, J.E., and Schnabel, G. Cleary's 3336 EG at 12 to 16 oz/100 gal water.Terraguard SC at 4 to 8 fl oz/100 gal water.Use with oils or adjuvants may cause plant damage. Spirato GHN at 2 to 4 fl oz/100 gal water.Sil-Matrix at 1 to 4 quarts/100 gal water plus a nonionic surfactant.Reapply if rain occurs within 12 hours of original application. Avoid excessive runoff to small plants, which may result in stunting and/or chlorosis. Do not use with organosilicone-based adjuvants. Using with oils or adjuvants may damage plant. Medallion WDG at 2 to 4 oz/100 gal water.Protect DF at 1 to 2 lb/100 gal water plus 2 to 4 oz spreader-sticker.Fore 80 WP at 1.5 lb/100 gal water plus a spreader-sticker.Mancozeb-based products can be used as mixing partners and provide some protection.Decree 50 WDG at 0.75 to 1.5 lb/100 gal water."Knock Out" and "Double Delight" roses can be sensitive resulting in damaged foliage. Daconil Weather Stik at 1 pint/100 gal water.Chipco 26019 FLO at 1 to 2.5 quarts/100 gal water.Captan 80 WDG at 1.5 lb/100 gal water.Broadform at 4 to 8 fl oz/100 gal water. Astun at 10 to 17 fl oz/100 gal water.Hi-Yield Captan 50 W Fungicide may be used in home gardens at 2 Tbsp/gal water.Good to mix or alternate with FRAC group M3 or M5 fungicides. Alternate or tank-mix materials with different modes of action to prevent developing resistant fungal populations. Resistance to FRAC groups 1, 2, 7 and 9 have been detected in cut roses coming in from out of the country. Use calcium nitrate, gypsum, or similar calcium source topdressed or incorporated into container media.Ĭhemical control Use as a foliar spray, but focus on cultural controls.Use drip rather than overhead irrigation.Space plants for adequate air movement.If using DROP or DIP for size control, do not let humidity rise above 90%. Heating in the morning before sunup can also help prevent dew formation as air temperature increases faster than the temperature of plant parts. Heating the greenhouse at night (especially for zero or negative DIF) or venting around sunset may be necessary.
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