Infection can occur in most any garden. The pathogen enters through wounds to the plant caused by improper and unsanitary pruning, grafting, mechanical injury during cultivation, or failure to prune away broken stems and roots during transplanting. Bacteria can survive in the soil for at least two years. Besides spreading via infected pruning equipment, insects and water are also known vectors.
Crown Gall - Unlike the galls formed by stinging insects which are normally harmless to the tree or plant, Crown Gall is caused by a bacteria. These galls begin with tumor-like cell growth at or just below the soil's surface, near the base of the plant and commonly on bud unions. Galls usually begin as green, pliable tissue; then develop into dark, crusty growths. Following gall formation, shrub growth is stunted, foliage is sparse, and bloom production is reduced.
Root Gall- Like Crown Gall above, but damage is confined to roots. Commonly caused by improper root pruning during transplant.
Stem Gall - Like Crown Gall above, but damage is confined to stems and canes above the soil's surface.
Control of bacterial diseases is achieved by checking existing and newly introduced plants for contamination. Use caution when cultivating fertilizers, organic materials or mulches around the rose's root zone. If galls are discovered, the plants should be removed as soon as possible. Replace contaminated soil with well-draining soil high in organic matter and beneficial microbial activity. When planting bare-root roses, prune broken or damaged roots and stems with disinfected pruning equipment. Dip pruning tools with a 10% liquid chlorine bleach and water solution. Disinfect tools between each plant when pruning non-infected plants; between each cut when pruning infected plants. (Note: This may discolor metal parts. After disinfecting, scrub discolored areas with steel wool, sharpen cutting edges, and oil metal surfaces to restore them.) Some rosarians also report success by pruning away galls and spraying the infected area with an anti-bacterial solution like Agri-strep or a copper compound like Kocide.
Viral Diseases
Viruses are smaller than bacteria. As such, they rely on living organisms for dispersal in the garden. In roses, their spread is chiefly caused by grafting infected scions, buds and/or root stocks; although some can be vectored by parasitizing, chewing or sucking insects.
There are currently no chemical solutions for curing roses infected with a virus. The best control is to remove the rose, replace the surrounding soil, and inform the nursery or mailorder firm where you obtained the plant.
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