IPM OF ROSE DISEASES
Baldo Villegas
Entomologist; ARS Master Rosarian
Sacramento, California USA (USDA Zone 8/9)
An America Rose Society Presentation ©2005
IPM STRATEGIES
 Prevention
 Pest
& Symptom Identification
 Regular Survey for Pests (presence or symptoms)
 Establish Action Thresholds & Guidelines
 Take the appropriate action. “No action” might be
the appropriate action
PLANT DISEASE TRIANGLE
 Susceptible
Host
 Available Pathogen
 Right environmental
conditions
TYPES OF DISEASE ORGANISMS
 Fungi
 Bacteria
 Viruses
 Nematodes
 Abiotic
Factors
ROSE DISEASES - INFECTIOUS
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Fungal Diseases
Powdery Mildew
Black Spot
Rust
Verticillium Wilt
Downy Mildew
Cankers
Botrytis
 Anthracnose
 Crown
Gall
 Rose Mosaic
 Rose Spring Dwarf
 Rose Rosette
 Rose Wilt
 Root Nematodes
ROSE DISEASES – NON-INFECTIOUS
 Physiological
Problems
 Genetic Disorders
 Nutritional Deficiencies
 Nutritional Toxicities
 Environmental Imbalances
 Salinity
 Air Pollution
 Oxygen Deficiency
 Heat & Moisture Stress
 Pesticide Toxicity
FUNGAL DISEASES
 Powdery
Mildew - Sphaerotheca pannosa (Wallr. Ex Fr.)
Lèv.
 Blackspot - Diplocarpon rosae Wolf
 Rust - Phragmidium spp. – 9 species have been found
 Botrytis Blight - Botrytis cinerea (Pers. Ex Fr.)
 Cankers – several types caused by several fungi
 Spot Anthracnose - Sphaceloma rosarum (Pass.) Jenkins
 Downy Mildew - Peronospora sparsa Berk.
Other Fungal Diseases
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Verticillium Wilt - Verticillium spp.
Oak Root Fungus - Armillaria mellea Vahl ex Fr.
“Cankers”
1. Brand Canker
2. Common Canker (Graf Canker) - Coniothyrium fuckelii
Sacc.
3. Brown Canker - Cryptosporella umbrina (Jenkins) Jenkins
& Wehm. [Diaporthe umbrina Jenkis=imperfect stage]
4. Canker (Dieback) – caused by several fungi [Elsinoë
rosarum=perfect stage]
Leaf Spots – several fungi cause leaf spots, a sample has to be
submitted for proper diagnosis
DISEASES CAUSED BY FUNGI
General Control Considerations
 Acquire
 Remove
resistant varieties of roses, if available
infected plant material as soon as it is
noticed and get rid of plant materials after pruning
 Avoid overcrowding and choose open beds away
from fences and wind obstructions
 Open the center of the plants when you prune to
provide air circulation through the leaf canopy
DISEASES CAUSED BY FUNGI
General Control Considerations (cont.)
 Avoid
overhead irrigation/sprinklers; Water early in
day to allow leaves to dry
 Sterilize tools between pruning, especially if you’ve
cut through a diseased cane
 Avoid injury to rose canes; use sharp tools to obtain
clean cuts
TYPES OF FUNGICIDES
Based On Mode Of Action
 PROTECTANT - Applied
before infection of
fungus spores
 ERADICANT - Applied after infections appear
and kills on contact
 SYSTEMIC - Translocated by leaves and roots
and distributed in the plant to prevent infection
GARDEN FUNGICIDES - Systemic
GARDEN FUNGICIDES - Contact
Powdery Mildew - Diagnosis
Note White Mycelia On The Surface Of Leaves
Powdery Mildew - Pictures
POWDERY MILDEW
Pathogen: Sphaerotheca pannosa (Wallr. Ex Fr.)Lèv.


SYMPTOMS: White growth of the fungus consists
of mycelium and conidiophores and appears as
patches on leaves and stems. Young tissue is most
susceptible.
CONDITIONS: Night temperature of 15.5°C [60°F]
and relative humidity of 90-99%; Day temperature
of 26.7°C [80°F] and 40-70% RH. Warm season
disease; does not require free moisture for spore
germination.
POWDERY MILDEW
Pathogen: Sphaerotheca pannosa (Wallr. Ex Fr.) Lèv.

CONTROL:
1. Many cultural methods are available
2. Spray with available protectant or systemic
fungicides
3. Sodium and Potassium Bicarbonate have shown
fungicidal activity
4. Some antitranspirants have shown fungicidal
activity by acting as a barrier to invading spores
Blackspot – Note Fringed Borders In Spots
BLACKSPOT
Pathogen: Diplocarpon rosae Wolf
 SYMPTOMS:
Characteristic black spots develop
on the upper leaf surfaces. Leaf spots are usually
circular with characteristic fringed borders.
Raised purple-red, irregular blotches may develop
on young canes of susceptible varieties.
 CONDITIONS: The fungal spores (conidia) must
be immersed in water and must be continuously
wet for at least seven hours for any infection to
occur. Needs free moisture.
BLACKSPOT
Pathogen: Diplocarpon rosae Wolf
 CONTROL:
1. Many cultural methods are available
2. Spray with available protectant or systemic
fungicides
3. Leaves should not be allowed to remain wet or
at very high humidity for more than 7-12 hours
4. Pick off some of the lower leaves near the
ground, but avoid causing sun-burn of the budunion & lower canes
Rust – Note Orange & Black Pustules
RUST
Pathogen: Phragmidium spp. (9 species)

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SYMPTOMS: Powdery pustules of orange to orangered spores (aeciospores/uredospores) on the
undersides of the leaves in mid spring through fall
are very diagnostic. Black pustules containing
teliospores may be present during the winter months.
Fungus is an obligate parasite.
CONDITIONS: The optimal conditions for disease
development are temperatures of 18-21°C [64-70°F]
and continuous moisture for two to four hours. Note:
Needs free moisture.
RUST
Pathogen: Phragmidium spp. (9 species)

CONTROL:
1. Many cultural methods are available
2. Spray with available protectant or systemic
fungicides
3. Avoid wetness of the leaves or high humidity
around the foliage for longer than two hours
4. Pick off some of the lower leaves near the ground,
but avoid causing sun-burn of the bud-union &
lower canes
Botrytis Fungus - Diagnosis
BOTRYTIS BLIGHT
Pathogen: Botrytis cinerea Pers. Ex Fr.


SYMPTOMS: Grayish brown mycelial growth
is very characteristic of this fungus. It is a pest
of stored and refrigerated roses, rose buds (that
can't open), cut flowers, rose plants, and cuttings
used for propagation. Also on canes as a
secondary low level pathogen on tissue or
flower petals.
CONDITIONS: Cool temperatures, high
humidity, and moisture. It needs free moisture.
BOTRYTIS BLIGHT
Pathogen: Botrytis cinerea Pers. Ex Fr.

CONTROL:
1. Spray with available protectant or systemic
fungicides when weather conditions are favorable
2. Practice strict sanitation, especially with infected
flowers. Dispose of any flowers showing brown
petals
3. Discontinue overhead watering in cool, humid
weather conditions
4. Biological control methods are being looked at but
they are not available commercially yet
“Canker” – Several Fungi Involved
“CANKER”
Several Types Of Cankers Present & Collectively Called “Cankers”


SYMPTOMS: Wounds are necessary for infection.
Canker begin as small yellow to red spots in the
bark and gradually expand. The centers of the
cankers become light brown and the margin a
darker brown
CONDITIONS: Cool moist weather conditions.
Free moisture may be needed
“CANKER”

CONTROL:
1. Spray with available protectant or systemic fungicides when weather
conditions are favorable; apply dormant sprays if there is a history of
infection in the rose garden; cover any pruning cuts & wounds with
dormant sprays or with in-season fungicidal sprays
2. Practice strict sanitation during the pruning season by pruning off
infected canes and avoid scrubbing the budunion with harsh brushes
3. Sterilize cutting tools if contaminated
4. Prune out any damaged canes and avoid unnecessary wounds to
stems during the growing season
5. Discontinue overhead watering in cool, humid weather conditions
SPOT ANTHRACNOSE
Pathogen: Sphaceloma rosarum (Pass.) Jenkins
Note solid border of spots often with
a reddish halo and grayish center
Downy Mildew - Diagnosis
Downy Mildew - Diagnosis
DOWNY MILDEW
Pathogen: Peronospora sparsa Berk.


SYMPTOMS: This fungus is characterized by
purplish to black areas on leaves, stems, and
peduncles. This is followed by yellowing of the
leaflets and complete defoliation of the plant. The
fungal mycelia are intercellular in rose tissue. Fungus
is an obligate parasite
CONDITIONS: Humid, cool conditions are ideal for
this fungus. Early spring and late fall disease. It
needs free moisture
DOWNY MILDEW
Pathogen: Peronospora sparsa Berk.

1.
2.
3.
CONTROL:
Open up center of plant to allow for cross ventilation
Avoid overhead watering during cool weather
Use preventative fungicides
– Protectants: Fungicides like Manzate, Mancozeb
(Fore®) and others containing chlorothalonil
(Daconil 2787® & FungiGard®)
– Systemic fungicides such as Aliette and others
containing metalaxyl have been used for
controlling this fungus
Bacterial Crown Gall - Diagnosis
BACTERIAL CROWN GALL
Agrobacterium tumefaciens E. F. Sm. & Town) Conn


SYMPTOMS: gall formations on the crown,
roots, and even twigs are characteristic
CONDITIONS: Bacterial pathogen enters plant
through wounds, either natural or caused by
pruning, grafting, or mechanical injury by tools.
The Bacteria persistent in soil for long time and
easily moved by moving soil or transplanting
BACTERIAL CROWN GALL
Agrobacterium tumefaciens E. F. Sm. & Town) Conn

CONTROL:
1. Buy disease-free plants; examine new plants for galls or
gall-like growths on roots, crown & stems
2. Avoid injury to roots, crown, stems while planting or
cultivating.
3. Plant in soil that has been properly treated or sterilized
4. Remove infected plants as soon as galls are observed.
Remove soil from near infected parts and make sure that as
many infected roots as possible are discarded. Surgical
removal of galls might only work temporarily
BACTERIAL CROWN GALL
Agrobacterium tumefaciens E. F. Sm. & Town) Conn

CONTROL (cont.):
5. Sterilize all pruning tools and even gloves when handling
or cutting into galls: 0.5% bleach; Lysol aerosols;
denatured alcohol, etc.
6. Use biological antagonists (e.g., Gallex®, Galltrol®, etc.)
- Gallex® is a ready-to-use emulsion applied directly
with brush
- Galltrol® is a culture of live bacteria. It is applied as a
dip or spray on seeds, cuttings, and bareroot plants
Rose Mosaic Virus Complex
Rose Mosaic Virus Complex - Symptoms
“ROSE MOSAIC VIRUS”
A Complex of Several Viruses
 Prunus
Necrotic Ringspot Virus (PNRSV)
 Apple Mosaic Virus (ApMV)
 Arabis Mosaic Virus (AMV)
ROSE MOSAIC VIRUS COMPLEX


SYMPTOMS: Visible symptoms are variable but
include chlorotic line patterns, ring spots, and mottling
of leaves and some flower break. Malcolm Manners
reports some loss in flower production and plant vigor.
Foliar symptoms detract from the overall quality
CONDITIONS: Mosaic Virus transmission in roses
appears to be limited to vegetative propagation when
virus infected buds, scions, or rootstocks are grafted to
healthy plants. However, Prunus Necrotic Ringspot
Virus (PNRS) and Apple Mosaic Virus (APMOV) may
be pollen transmitted
ROSE MOSAIC VIRUS COMPLEX
CONTROL:
1. No chemical controls are currently available
2. Buy disease-free roses; buy only “certified virus-free”
roses or budwood
UC Davis Foundation Plant Materials Service
(FPMS)
Malcolm Manners – Florida
J&P advertises virus indexed roses in 2001?
Impossible to see rose mosaic virus symptoms in
bareroot roses

ROSE MOSAIC VIRUS COMPLEX

CONTROL (cont.):
3. Graft or propagate only from “healthy” plants or
certified virus free sources or budwood
4. To be on the safe side, sterilize cutting tools especially
after pruning infected plants
Rose Spring Dwarf Disease - Diagnosis
Rose Spring Dwarf Disease - Diagnosis
ROSE ROSETTE DISEASE
SYMPTOMS: Weird, “witches broom” type foliage, usually bright
red in color
CONDITIONS: Commonly found on Rosa multiflora and related
roses
AGENT: It is believed that the eriophyid mite, Phyllocoptes
fructiphilus Keifer , is the responsible vector for the spread of this
disease. The causal agent is not known. It is widely speculated
that it is a virus transmitted to the plant from the mite or a allergic
reaction to the mite’s bite by the plant
CONTROL: There is no known control, other than pruning off the
affected areas or total removal of the plant
Rose Rosette Disease - Diagnosis
Rose Rosette Disease - Distribution
Nematode Infection On The Roots
PLANT PARASITIC NEMATODES
 Dagger
Nematodes - Xiphinema sp.
 Lesion Nematodes - Pratylenchus sp.
 Root-knot Nematodes - Meloidogyne hapla
Chitwood
 Other species of plant parasitic nematodes have
been isolated from roses
ABIOTIC DISEASE-LIKE SYMPTOMS
 Physiological
Problems
 Nutritional Imbalance
 Water
 pH Imbalance
 Environmental Extremes
 Air Pollutants
 Pesticide Injury
 Drainage
Abiotic Disease-like Symptoms
Nutritional Imbalances
Dehydration
Herbicide Drift
Herbicide Drift On Roses
IPM IN THE HOME GARDEN
 Establish
damage or threshold levels for yourself
 Make observations and record them
 Correctly identify the pest
 Take the appropriate action
The End