Janell Stevens JohnkAssistant Professor and Extension Plant Pathologist

The Texas A&M University System

Issued in furtherance of Cooperative Extension Work inAgriculture and Home Economics, Acts of Congress ofMay 8, 1914, as amended, and June 30, 1914, incooperation with the United States Department ofAgriculture. Edward A. Hiler, Interim Director, TexasAgriLife Extension Service, The Texas A&M UniversitySystem.

5,000 copies, Revised PP

The information given herein is for educationalpurposes only. Reference to commercial products orcompanies is made with the understanding that nodiscrimination is intended, and no endorsement by theCooperative Extension Service is implied.

1. Plant roses in full sun.

2. Use drip irrigation or soakerhoses.

3. Water in early morning.

4. Selectively prune to opencanopy and increase aircirculation.

5. Manage weeds and insects toprevent the spread of viruses.

Five Steps to Healthy RosesFive Steps to Healthy Roses

Educational programs of the Texas AgriLife ExtensionService are open to all people without regard to race,color, sex, disability, religion, age or national origin.

CommonRose

D I S E A S E S E R I E S

L-51723-98

Diseases

•Keep leaves dry.The fungus requires leaf wetness tocause infection. So keep leaves dry by:

•Planting roses in full sun. •Using drip irrigation or soaker hoses. •Watering in the early morning.

•Apply fungicides.Susceptible roses will need fungicideapplications during times of favorableenvironmental conditions. During springand fall, when rains are more frequentand cool temperatures form dew, manyroses - even those with some resistance-will probably need to be sprayed.

SymptomsAffected leaves have black spots withfringed edges. Leaves may turn yellow.Severe infections cause leaves to dropprematurely. Repeated defoliationstresses the plant, making it moresusceptible to insect problems andother diseases.

Management•Prune damaged orinfected canes.The black spot fungusover winters oncanes. Carefulpruning removesdamaged or infectedcanes and slowsdisease development.

Black Spot

Rose varieties differ in theirsusceptibility to black spot fungus.While many newer varieties werescreened for disease resistance, someolder varieties and antique roses arealso somewhat resistant. However,many hybrid tea roses are susceptible.

Powdery Mildew

Powdery mildew is also caused by afungus. While black spot is a problem inthe spring and fall, powdery mildew canbe a problem spring, summer and fall.

SymptomsWhitish patches appear on infectedleaves. The leaves may pucker in somevarieties.

ManagementPowdery mildew fungus doesn’t needleaf wetness to cause infection, but itdoes need high humidity at the leafsurface. Reduce the humidity by:

•Planting roses in full sun. •Watering in early morning.•Selective pruning to open the canopy

and increase air circulation.

Fungicide application may be necessaryfor susceptible rose varieties.

Viruses

Viruses are often spread by insectssuch as leaf hoppers, or through graftunions. There is no chemical for viruscontrol.

SymptomsLeaves aremottled yellowand green.Leaves may becrinkled,puckered ordistorted.Symptoms areeasiest to seeon new leaves.

ManagementRemove infected plants because they arethe source of the virus for insects tospread to other roses. Weed control isimportant because weeds can serve as areservoir for the virus and a home toinsect vectors.