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Rose Diseases:

Here is a list of links for recommended reading on various diseases:

Diseases Of Roses And Their Control, Alabama Cooperative Extension System www.aces.edu/department/ipm/Anr505.htm

American Rose Society articles on diseases www.ars.org/explore.cfm/diseases/

Mildews:

Mildew will reappear each year as the spores overwinter in debris and on the soil, and are spread by both water (splashing) and wind. Favourable weather can enable it to establish a primary infection within a week, and reinfect plant-to-plant within hours.

Plant Pathology Update, Mildews by Dr. Larry W. Barnes: Texas A&M University hortipm.tamu.edu/publications/Pathup1.html
Athracnose, Blackspot and Downy Mildew compared by Paul Desmet: www.cruzio.com/~rbedard/devor/spots/index.html
Photos of diseases, by Baldo Villegas www.jps.net/rosebug/irosepests.html#POWDERY%20MILDEW

Control:

Thin your roses and or space them farther apart to increase air flow and reduce humidity
Avoid wetting of leaves during watering
Plant mildew resistant varieties
Spraying: Sprays against mildew are mostly preventative - that is, they will help prevent the spread but will not cure an infection once the fungus has colonized the leaf. Therefore, they need to be sprayed early and regularly before the onset of the infection
Follow directions and check your local laws first.
- For Powdery mildew, spray with
  - Copper, Abound, Ziram, Mancozeb, Maneb, and Captan will also provide protection against Downy mildew, or
  - sulphur, Bayleton, Rubigan, or Rally - these are effective against Powdery but ineffective against Downy mildew,
- For Downy mildew, as a preventative, spray with a product containing copper, Captan or Mancozeb, Dithane M45, Manzate 200, Zyban, Ziram, Maneb, Aliette, Subdue, Pace, and others containing both manganese and zinc.
  - Ridomil Gold Copper and Abound have been suggested as curatives once the rose is infected.
  - You will find Captan or Mancozeb in some lawn fungicide products. If it is effective, it is more available and less expensive than some other formulations. We've used it, it seemed to work but our main objection to the lawn fungicide we tried was the ugly white deposits the solution left on the leaves.
- Benomyle (Benlate) and Rovral do not appear to be effective against mildew
Strip infected leaves as soon as possible to prevent secondary infection
Scrupulously clean the soil surface of ALL old leaves, petals, any debris.
In the dormant season strip the bush of foliage, prune back and spray with copper. Bordeaux mixture is copper and lime sulphur. Copper is effective for Downy, sulphur for Powdery mildew). Some people also spray the soil surrounding the rose.

Powdery Mildew - Sphaerotheca pannosa

Downy Mildew - Peronospora sparsa

American Rose Society www.ars.org/experts/downy.html

The University of California Cooperative Extension, Tulare County. www.ucce.tulare.ca.us/pubgrape/ipm196.htm

Other Fungal Diseases

Blackspot - Diplocarpon rosae
Dark purple or black spots with indistinct edges on the leaf surface, leaf will yellow and drop. Affects the lowest leaves on the plant first.

Athracnose - Sphaceloma rosarum
Dark spots with well-defined edges, leaf generally stays green.

Rust - Phragmidium mucronatum
Pinhead sized orange nodules on the underside of the leaf.

Primary care for all of these fungal diseases is to strip infected leaves and remove all old leaves, petals, and any debris from the ground.

Viral diseases

Rose Rosette

A relatively rare viral disease most commonly found in R. multiflora, which is highly susceptible, and roses grafted on infected multiflora rootstock. The responsible organism is thought to be a virus that is spread by mites.

Rapid new growth with unusually dense prickles, large canes colored bright red or purple, leaf growth is badly stunted. Then lateral growth develops with many, closely spaced petioles (also called "witches broom") and leaf buds fail to open or appear rosetted. Roses usually die within two years of showing symptoms. Infected roses complete with their roots should be removed from gardens as quickly as possible and burned. Do not simply prune off the distorted canes - the disease is viral and affects the whole plant. Eliminating stands of "wild" (naturalized) R. multiflora within 1/4 mile may help by reducing mite-borne infection (this is obviously difficult for the gardener to do if these stands are not on their property).

Texas A & M cygnus.tamu.edu/Texlab/Shrubs/Rose/rrr.html

Just Roses www.markw.com/rosette.htm

Rose Mosaic

A disease of the rootstock - not generally transmissible. The best defence is to buy roses from sources that use certified virus-free stock.

Tobacco Mosaic

Can be transmitted from tomatoes to roses by contact or through infected material on or in the soil.

Rose Diseases:

Mildews:

Other Fungal Diseases

Viral diseases

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