Tuesday, June 7, 2016

Rose Rosette - A Devastating New Rose Disease in Indiana

Rose rosette is a quickly spreading disease that is a threat to virtually all cultivated roses (Rosa spp.) in Indiana, regardless of cultivar. Even rose cultivars known for their exceptional disease resistance and hardiness are susceptible to rose rosette disease. Losses can occur in home and commercial landscapes, nurseries, and botanical garden plantings.

Rose rosette symptoms are initially observed during spring, intensifying as the season progresses. Symptoms are highly variable, depending on cultivar, plant age, and growing conditions. 
Some common symptoms include: 
•   Increased growth/rapid elongation of shoots 
•   Abnormal red discoloration of shoots and foliage 
•   Witches broom (prolific clustering of small shoots) 
•   Spiral pattern of cane growth
•   Shortening of internodes (shorter stem length between leaves) 
•   Distorted or dwarfed leaves 
•   Overabundance of thorns 
•   Atypical flower coloration (e.g. mottling of otherwise solid-colored roses) 
•   Deformed buds and flowers 
•   Increased susceptibility to other diseases, such as powdery mildew
•   Lack of winter hardiness

The disease-causing agent has only recently been identified as a virus, which has been named rose rosette virus (RRV). RRV is transmitted by an eriophyid mite and through grafts. Once introduced into a plant, the virus becomes systemic.

Growers should take precautions to reduce the risk of introduction of rose rosette virus. There is no cure for rose rosette disease once bushes become infected. Thus, early detection is essential to prevent the virus from spreading to nearby roses.

Infected plants, including roots, must be removed completely, Diseased plants should be immediately bagged and removed from the vicinity so that the pathogen is not spread to healthy plants. Alternatively, where permitted, infected plants may be destroyed by burning. Care must be taken when digging diseased plants to avoid scattering disease-carrying mites to nearby rose shrubs. Remove and destroy any regrowth that occurs from roots remaining in the soil after rose rosette-infected plants are removed. 

Exerpts taken from this publication from University of Kentucky. Rose Rosette Disease -PPFS-OR-W-16.

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