Viral disease dooms rose bush


June 14, 2008|By Ellen Nibali and Jon Traunfeld | Ellen Nibali and Jon Traunfeld,Special to the Sun

My rose bush looks weird. Some leaves are small and "spidery" and reddish. Some stems are covered with extra little thorns. Is this caused by the unusually cool spring?

You are describing symptoms of rose rosette disease. This virus is transmitted by eriophyid mites blown from infected roses located upwind from your rose. Infected roses die in about two years. There is no cure and the mites are not controllable. Dig up your infected rose right away, so the virus does not spread to your healthy roses.

Many of the invasive non-native Rosa multiflora roses are infected with rose rosette disease. Remove those nearby, especially upwind from your roses. Plant new roses upwind from rosa multiflora roses if you cannot remove the existing ones.

I plan to plant a row of evergreens using soil from the hole mixed with peat moss at a 50/50 ratio. Do I fertilize now?

Use much less organic matter in the planting hole. Ten percent is plenty. In order for plant roots to grow outward, the soil in the hole must be similar to the surrounding soil. A hole with too much organic matter encourages the roots to stay inside the hole, circling around. Peat moss actually repels water when it is dry and is fairly expensive. Compost is a better choice.

Young trees should establish roots for a couple of years before getting much fertilizer. High nitrogen fertilizer encourages tender growth that is attractive to insects. This comes at the expense of growing drought- and disease-resistance trees. It is OK however, to plant the trees in a very sandy, low-fertility soil.

To get trees off to a good start, keep them well watered from spring to fall for two years. Mulch to conserve soil moisture and keep down weed competition.


*Check the underside of leaves that have a black film. This sooty mold is usually caused by scale insects.

*Watch for fungal disease in old beds of English ivy, pachysandra, or vinca. Clean out accumulated leaves and thin out plants to improve air circulation.

Ellen Nibali, a horticulture consultant, works at Maryland Cooperative Extension's Home and Garden Information Center, and Jon Traunfeld is the director of the Home and Garden Information Center. The center offers Maryland residents free gardening information. Call the center's help line at 800-342-2507 or e-mail plant and pest questions through the Send a Question feature at

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