Rose Diseases

Disease	Symptoms	Pathogen/Cause	Management
Anthracnose	Dark-purple to black spots are bordered by a narrow, dull-brown band. Centers of spots turn gray 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	Plant resistant cultivars (see note at the end of fact sheet). 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, chlorothalonil + thiophanate methyl, myclobutanil, copper hydroxide, azoxystrobin, propiconazole, mancozeb, thiophanate methyl, thiophanate methyl + mancozeb, triforine or ziram. 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 to insure good air circulation. Remove fading flowers and yellowing leaves. Apply azoxystrobin, chlorothalonil, fenhexamid, fludioxonil, or iprodione to protect healthy tissue.
Cankers	Reddish-brown spots on canes turn light to dark brown and become covered with tiny black dots (fungal fruiting structures). Cankers girdle and kill the cane.	Coniothyrium fuckelii, Cryptosporella umbrina, Coniothyrium wernsdorffiae, Cylindrocladium scoparium	Do not plant stock with cankers. Remove 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 that form on stems may enlarge to 6 inches in diameter. Galls can form on roots or stems.	Agrobacterium tumefaciens	Do not plant infected material. Apply Agrobacterium radiobacter to protect healthy plants.
Damping-Off	Cuttings fail to root, defoliate, and die. Roots are killed.	Pythium sp.	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 during cool, damp spring weather. Leaves yellow and fall. Small spots or long purplish areas may form on and kill twigs.	Peronospora sparsa	Water in a manner that keeps leaf surfaces dry. Apply azoxystrobin, mancozeb 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 Ampelomyces, chlorothalonil, fenarimol, piperalin, kresoxim methyl, myclobutanil, sulfur, triadimefon, potassium bicarbonate, copper hydroxide, azoxystrobin, triflumizole, triforine, or ziram. Triadimefon can stunt many cultivars.
Viruses	Leaves may exhibit mosaic, mottling, yellow line or ring patterns. Veins may turn yellow.	Rose mosaic, mottle, yellow mosaic, ring pattern, or streak virus; tobacco streak; rose rosette, rose wilt, spring dwarf, or color break virus; strawberry latent ringspot	Destroy infected plants. Plant only healthy, virus-free plants. Maintain good insect and mite control.

Black spot resistance: The fungus that causes rose black spot is a highly variable with many different races, each of which attacks different cultivars. As a result, it is difficult to identify cultivars that are resistant to all races of the fungus. Moss roses, Wichurainas, and rugosa hybrids exhibit some resistance. Tea roses, perpetuals, Austrian briers, polyanthas, and Pernetianas are susceptible. The following cultivars are listed as having some resistance to black spot: David Thompson, Bebe Lune, Coronado, Ernest H. Morse, Fortyniner, Grand Opera, Lucy Cromphorn, Sphinx, Tiara, Carefree Beauty, and Simplicity.

COMMON NAME	TRADE NAME
Ampelomyces quisqualis	AQ10 (biological control agent)
Agrobacterium radiobacter	Galltrol A
azoxystrobin	Heritage
chlorothalonil	Daconil 2787
chlorothalonil + thiophanate methyl	ConSyst
copper	Tenn-Cop 5E, Kocide, Basicop
fenarimol	Rubigan
fenhexamid	Decree
ferbam	Carbamate
fludioxonil	Medallion (greenhouse use only)
iprodione	Chipco 26019
kresoxim methyl	Cygnus (greenhouse use only)
mancozeb	Dithane, Protect T/O, PathGuard
mancozeb + thiophanate methyl	Duosan, Zyban
mefenoxam	Subdue Maxx
metalaxyl	Subdue
myclobutanil	Systhane
PCNB	Defend, Terraclor
piperalin	Pipron
potassium bicarbonate	Kaligreen, Armicarb, FirstStep, Remedy
propiconazole	Banner
sulfur	Sulfur, Lime Sulfur, Micro Flo, Microsperse
triadimefon	Bayleton
triflumizole	Terraguard ( greenhouse or other closed structure use only)
thiophanate methyl	Clearys 3336, Domain FL
triforine	Funginex
ziram	Ziram