Rose Diseases (Greenhouse)
Gary W. Moorman, Professor of Plant Pathology
|ANTHRACNOSE||Dark purple to black spots are bordered by a narrow, dull brown band. Centers of spots turn grey and fall out. Spots form on canes, similar to leaf spots.||Sphaceloma rosarum||Maintain good sanitation. Black spot control procedures (below) also control anthracnose.|
|BLACK SPOT||Brown to black round spots with feathery edges form on leaves. Leaves yellow and fall. Small, purplish spots form on canes.||Diplocarpon rosae||Remove infected canes. Remove and destroy fallen leaves. Water in a manner that keeps foliage surfaces dry. Apply one of the following to protect new foliage: chlorothalonil, propiconazole, neem oil, mancozeb, thiophanate methyl, thiophanate methyl + mancozeb, chlorothalonil + thiophanate methyl, copper hydroxide, ziram, captan, trifloxystrobin, or triforine. Triadimefon can stunt some cultivars.|
|BOTRYTIS BLIGHT||Small water-soaked lesions form on petals. Gray fungal growth covers infected petals. Stubs left after harvest become infected. The fungus then moves down to girdle the cane.||Botrytis cinerea||Space plants and provide ventilation to avoid excessively high humidity. Remove fading flowers and yellowing leaves. Apply chlorothalonil, dichloran, trifloxystrobin, fenhexamid, iprodione, or azoxystrobin to protect healthy tissue. Heat and ventilate to maintain low humidity.|
|CANKERS||Reddish-brown spots on canes turn light to dark brown and become covered with tiny black dots. Cankers girdle and kill the cane.||Coniothyrium fuckelii, Cryptosporella umbrina, Coniothyrium wernsdorffiae, Cylindrocladium scoparium||Do not plant stock with cankers. Removed infected canes making the cut immediately above a bud. Apply a fungicide (see black spot) after pruning. Sterilize the shears with bromine disinfestant between cuts. Maintain even soil moisture and fertilization.|
|CROWN GALL||Small white to cream-colored galls form on stems. Galls may enlarge to 6 inches in diameter. Galls can form on roots or stems.||Agrobacterium tumefaciens||Do not plant infected material. Steam sterilized beds where infected plants were grown. Remove and destroy infected plants. Apply Agrobacterium radiobacter to protect healthy plants.|
|DAMPING-OFF||Cuttings fail to root, defoliate and die. Roots are killed.||Pythium||Pot and propagate in pasteurized media. Use clean, disinfested tools. Discard infected plants. Do not leave cuttings in mist beds for excessive periods. Pot as soon as rooted.|
|DOWNY MILDEW||Purplish-brown spots form on leaves. Leaves yellow and fall. Small spots or long purplish areas may form on canes and may kill twigs.||Peronospora sparsa||Heat and ventilate to maintain low humidity. Water in a manner that keeps leaf surfaces dry. Apply potassium phosphate, potassium salts of phosphorus acid, trifloxystrobin, mancozeb, azoxystrobin, dimethomorph, or mancozeb + thiophanate methyl.|
|POWDERY MILDEW||Spots on leaves, stems and flower parts expand and become covered with white fungal growth. Small dead spots form on some cultivars.||Sphaerotheca pannosa||Apply chlorothalonil, propiconazole, piperalin, fenarimol, surfur, copper hydroxide, neem oil, azoxystrobin, kersoxim methyl, ziram, or triforine. Triadimefon can stunt many cultivars used in greenhouse production.|
|VIRUSES||Leaves may exhibit mosaic, mottling, yellow line or ring patterns. Veins may turn yellow.||Rose mosaic, mottle, yellow mosaic, ring pattern, tobacco streak, rose rosette, rose wilt, spring dwarf, color break or strawberry latent ringspot virus||Destroy infected plants. Plant only healthy, virus-free plants. Maintain good insect and mite control.|
Black leaf spot.
Active Ingredients and Trade Names of the Chemicals
|FRAC Group No.||Risk Level||Class||Active ingredient||REI Restricted Entry Interval||Trade names (EPA Reg. No)|
|1||3||Benzimidazole||thiophanate methyl||12||3336 (1001-69), OHP 6672 (51036-329-59807), Fungo Flo (51036-329-59807), Systec 1998 (48234-12)|
|2||3||Dicarboximide||iprodione||12||Chipco 26GT (100-1138), Chipco 26019 (264-481), Iprodione (51036-361), Sextant (51036-361-59807)|
|Triazole||propiconazole||24||Banner MAXX (100-741), Propiconazole (51036-403), Spectator (62719-346-10404), Kestrel (66222-41-81943)|
|triadimefon||12||Strike (3125-436), Bayleton (432-1360)|
|Chloronitrile||chlorothalonil||48||Daconil (50534-9), Exotherm Termil (70-223)|
|12||Echo (60063-7), PathGuard (60063-7-499), Concorde (72167-24-1812), Pegasus (72167-24-1812)|
|Copper, fixed||copper hydroxide||48||Kocide (352-656), Champion (55146-1)|
|Dithiocarbamate||mancozeb||24||Dithane (707-180), FORE (707-87), Pentathlon (1818-251)|
|manganese + zinc||24||Protect T/O (1001-65)|
|U||1||Phosphite||phosphorus acid salts||4||Alude (71962-1-1001)|
|potassium phosphate||4||Vital (42519-24)|
|NC||1||neem oil||4||Trilogy (70051-2), Triact (70051-2-59807)|
Fungicides and Fungicide Resistance Management - Certain fungicides, usually systemic fungicides, are said to be 'at risk' to the development of resistance if they are used repeatedly. See the Risk Level in the above table (1 = low risk; 3 = high risk). The Fungicide Resistance Action Committee has developed a numbering system in which chemicals with the same FRAC Group number have the same mode of action (See http://www.frac.info/frac/index.htm ). It is recommended that chemicals at high risk be used sparingly and in rotation or mixed with chemicals with different modes of actions (different FRAC number).
|Biological Control Agent (type of organism)||Trade Name (EPA Reg. No.)||Target pathogen|
|Agrobacterium radiobacter (bacterium)||Galltrol A (strain 84) (40230-1)||Agrobacterium tumefacians|
|(crown gall)||Norbac 84C (strain K84) (38087-2)|
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