Dr. Alan Windham, plant-disease expert with the University of Tennessee Agricultural Extension Service, shares some tips for identifying and coping with common rose diseases. Fungal diseases are influenced by climate, so some are more prevalent in different parts of the country. - Blackspot, a widespread fungal disease, is indicated by dark circular spots with ragged edges. Generally, any spot on rose foliage is a sign of fungus disease. Prevention is the best cure: spray with a fungicide or dust with sulfur powder during the growing season; during winter, use a fungicidal dormant spray. Keep the rose bed free of fallen leaves: fungus spores overwinter in leaf debris.
- Downy mildew, another fungus, is indicated by the presence of irregular brown, black or purplish-red patches on foliage.
Downy mildew thrives in cool, wet weather. - Gray mold, or botrytis blight, forms on buds and on old blooms. To control the disease, simply cut off and throw away the infected flowers. Do not add them to your compost pile.
- Yellow streaks, rings and mottling on foliage are signs of rose mosaic, a viral disease. The plant will survive, but it won't grow as well, and the blooms will be smaller. Rose mosaic is spread through the propagation of infected plants and does not spread from plant to plant in the garden. If you buy a rose with these symptoms, return it to your garden center.
- The virus that causes rose rosette is spread by mites. Signs of infection are bright red leaves and wild growth called "witch's broom." The disease is fatal to the plant. Keep plants clean, and spray with insecticidal soap to prevent rosette.
- Crown gall is actually a tumor, bacterial in nature. Cure by pruning off the tumor, but remember to disinfect your pruning shears afterward with a weak solution of bleach.
- Canker is a fungus disease that causes cane dieback. Early on, it causes small yellow or reddish spots to appear; eventually the spots turn brown and grow larger, sometimes encircling the entire cane. Prune away the affected tissue.
RESOURCES :
For plants from Wolf River Valley Farms
Wolf River Valley Farms
Pall Mall, TN 38577
Fax: 1-931-879-5479
Email: pwpg@twlakes.net
Website: www.wolfriver.net
For tools from the Gardener's Supply Co.
Gardener's Supply Company
Burlington, VT 05401-2850
Fax: 800-551-6712 -or- 80
Email: info@gardeners.com
Website: www.gardeners.com
For the book A Year of Roses
The American Rose Society
The American Rose Society provides information on rose care, varieties and judging and contacts for local rose societies.
PO Box 30,000
Shreveport, LA 71130-0030
Phone: 318-938-5402
Fax 318-938-5405
E-mail: ars@ars-hg.org
Web site: www.ars.org
for the book Burpee Basics: Roses
Macmillan / Alpha Books
Website: www.macmillan.com
GUESTS :
Alan Windham
UT Agricultural Extension Service
5201 Marchant Drive
Nashville, TN 37211-5201
Phone: 615-832-6802
Fax: 615-832-0043
Email: awindham@cru.gw.utk.edu
Website: http://www.utextension.utk.edu
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