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

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 Verticillium Wilt - Verticillium spp. Oak Root Fungus - Armillaria mellea Vahl ex Fr. “Cankers”

1. Brand Canker2. 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 FUNGIGeneral Control Considerations

Acquire resistant varieties of roses, if available Remove 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 FUNGIGeneral 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 MILDEWPathogen: 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 MILDEWPathogen: Sphaerotheca pannosa (Wallr. Ex Fr.) Lèv.

CONTROL: 1. Many cultural methods are available2. Spray with available protectant or systemic

fungicides3. Sodium and Potassium Bicarbonate have shown

fungicidal activity4. Some antitranspirants have shown fungicidal

activity by acting as a barrier to invading spores

Blackspot – Note Fringed Borders In Spots

BLACKSPOTPathogen: 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.

BLACKSPOTPathogen: Diplocarpon rosae Wolf

CONTROL:1. Many cultural methods are available2. Spray with available protectant or systemic

fungicides3. Leaves should not be allowed to remain wet or

at very high humidity for more than 7-12 hours4. Pick off some of the lower leaves near the

ground, but avoid causing sun-burn of the bud-union & lower canes

Rust – Note Orange & Black Pustules

RUSTPathogen: Phragmidium spp. (9 species)

SYMPTOMS: Powdery pustules of orange to orange-red 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.

RUSTPathogen: Phragmidium spp. (9 species)

CONTROL:1. Many cultural methods are available2. Spray with available protectant or systemic

fungicides3. Avoid wetness of the leaves or high humidity around

the foliage for longer than two hours4. 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 contaminated4. 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 ANTHRACNOSEPathogen: Sphaceloma rosarum (Pass.) Jenkins

Note solid border of spots often with a reddish halo and grayish center

Downy Mildew - Diagnosis

Downy Mildew - Diagnosis

DOWNY MILDEWPathogen: 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 MILDEWPathogen: Peronospora sparsa Berk.

CONTROL: 1. Open up center of plant to allow for cross ventilation2. Avoid overhead watering during cool weather3. 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 GALLAgrobacterium 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 GALLAgrobacterium tumefaciens E. F. Sm. & Town) Conn

CONTROL:1. Buy disease-free plants; examine new plants for galls or

gall-like growths on roots, crown & stems2. Avoid injury to roots, crown, stems while planting or

cultivating.3. Plant in soil that has been properly treated or sterilized4. 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 GALLAgrobacterium 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 available2. Buy disease-free roses; buy only “certified virus-free”

roses or budwoodUC Davis Foundation Plant Materials Service (FPMS)Malcolm Manners – FloridaJ&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 rosesAGENT: 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 SymptomsNutritional 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