Wednesday, October 28, 2009

Landscape - Rose Mosaic Virus

I recently was sent some rose pictures that looked like the plant had rose yellow mosaic virus. The following is more information.

Several viruses are associated with the range of symptoms of rose mosaic, including Prunus necrotic ringspot virus (PNRSV) and Apple mosaic virus (ApMV). The disease does not spread naturally, has no known insect vector, but grafting transfers it to healthy plants. Viruses can be in the rootstock or scion or both and may not show symptoms. 'Madame Butterfly', 'Ophelia', and 'Rapture' are highly susceptible. Some report the disease does not spread; others indicate it may spread very slowly over many years.

Symptoms may range widely depending on time of year, temperature, and type of virus(es) infecting the plant. Characteristic symptoms include chlorotic line patterns (zigzag pattern), ringspots, and mottles in leaves sometime in the growing season. There may also be yellow net and yellow mosaic symptoms. Symptoms often are evident in spring and early summer but may not be on leaves produced in summer. Vein-banding may be on leaves in long hot periods. Flower distortion, reduction in flower production, flower size, stem caliper at the graft union, winter survival, and early leaf drop, and increase susceptibility to cold injury have all been reported. Some infected cultivars may not show any symptoms at all.

Note the irregular pattern of yellow lines on leaves.

Sometimes the leaf veins are yellow in plants infected with this virus.

Cultural control:

Purchase clean and/or certified virus-tested (and found to be free of all known viruses) stock. Remove and destroy infected plants. However, the disease will not spread unless you propagate from or onto an infected bush. Heat-treat scion stock plants 4 weeks at 100oF before grafting.

Information and photos from the Online Guide to Plant Disease Control from Oregon State University

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