IPM of Rose Diseases - American Rose Society

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.

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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. 

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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”

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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. 

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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 

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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