Rose Diseases (Greenhouse)

Informational table showing disease name, symptoms, pathogen/cause, and management of Rose Diseases (Greenhouse) diseases.
Rose Diseases (Greenhouse) - Articles

Updated: August 8, 2017

Rose Diseases (Greenhouse)
DiseaseSymptomsPathogen/CauseManagement
AnthracnoseDark 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 rosarumMaintain good sanitation. Black spot control procedures (below) also control anthracnose.
Black SpotBrown to black round spots with feathery edges form on leaves. Leaves yellow and fall. Small, purplish spots form on canes.Diplocarpon rosaeRemove 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 BlightSmall 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 cinereaSpace 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.
CankersReddish-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 scopariumDo 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 GallSmall white to cream-colored galls form on stems. Galls may enlarge to 6 inches in diameter. Galls can form on roots or stems.Agrobacterium tumefaciensDo 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-offCuttings fail to root, defoliate and die. Roots are killed.PythiumPot 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 MildewPurplish-brown spots form on leaves. Leaves yellow and fall. Small spots or long purplish areas may form on canes and may kill twigs.Peronospora sparsaHeat 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 MildewSpots on leaves, stems and flower parts expand and become covered with white fungal growth. Small dead spots form on some cultivars.Sphaerotheca pannosaApply chlorothalonil, propiconazole, piperalin, fenarimol, surfur, copper hydroxide, neem oil, azoxystrobin, kersoxim methyl, ziram, or triforine. Triadimefon can stunt many cultivars used in greenhouse production.
VirusesLeaves 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 virusDestroy infected plants. Plant only healthy, virus-free plants. Maintain good insect and mite control.


Black leaf spot.


Rust.


Anthracnose.


Virus symptoms.


Cankers.


Downy mildew.


Powdery mildew.

Active Ingredients and Trade Names of the Chemicals
FRAC Group No.Risk LevelClassActive ingredientREI Restricted Entry IntervalTrade names (EPA Reg. No)
13Benzimidazolethiophanate methyl123336 (1001-69), OHP 6672 (51036-329-59807), Fungo Flo (51036-329-59807), Systec 1998 (48234-12)
23Dicarboximideiprodione12Chipco 26GT (100-1138), Chipco 26019 (264-481), Iprodione (51036-361), Sextant (51036-361-59807)
32Pyrimidinefenarimol12Rubigan (62719-134)
Piperazinetriforine12Triforine (241-355)
Triazolepropiconazole24Banner MAXX (100-741), Propiconazole (51036-403), Spectator (62719-346-10404), Kestrel (66222-41-81943)
triadimefon12Strike (3125-436), Bayleton (432-1360)
5Piperidinepiperalin24Pipron (67690-1)
113Strobilurinazoxystrobin4Heritage (10182-408)
kresoxim-methyl12Cygnus (7969-124)
trifloxystrobin12Compass (432-1371)
172Hydroxyanilidefenhexamid4Decree (66330-35-67690)
40Cinnamic acid
derivativedimethomorph12Stature (241-419-67690)
M1Phthalimidecaptan96Captan (66330-29)
Chloronitrilechlorothalonil48Daconil (50534-9), Exotherm Termil (70-223)
12Echo (60063-7), PathGuard (60063-7-499), Concorde (72167-24-1812), Pegasus (72167-24-1812)
Copper, fixedcopper hydroxide48Kocide (352-656), Champion (55146-1)
Dithiocarbamatemancozeb24Dithane (707-180), FORE (707-87), Pentathlon (1818-251)
manganese + zinc24Protect T/O (1001-65)
ziram48Ziram (4581-140)
U1Phosphitephosphorus acid salts4Alude (71962-1-1001)
potassium phosphate4Vital (42519-24)
NC1neem oil4Trilogy (70051-2), Triact (70051-2-59807)
sulfur24Kumulus (51036-352)

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. 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)

Prepared by Gary W. Moorman, Professor of Plant Pathology