Infected plants exhibit distorted growth or galls on the lower stem. To identify, crown gall surface tissue is the same color and as firm as healthy plant tissue; and swellings cannot be rubbed off of the plant. Roots may appear gnarled, stunted or hairy with mostly small rootlets. Symptomatic plants may also be chlorotic, distorted, grow slowly, have small leaves, and because they're under stress, may be more susceptible to drought and other problems. Galls can crack and become infected with secondary pathogens. Herbaceous plants may be more seriously affected and possibly killed.
The most important management strategy for crown gall is sanitation. Clean tools, containers and work surfaces frequently and treat them with a commercial disinfectant, such as 10% bleach or 70% alcohol for at least 30 seconds. Purchase only high quality, disease-free stock; inspect plant stems and roots for galls prior to planting. Propogate from disease-free plants. Avoid plant injury (disease enters through wounds). Rogue infected plants. Crown gall will be a problem where previously infected plants have grown. Plant only non-host species, such as grass, for at least 3 years after removing all infected hosts. Soil fumigation is only partially effective and will not kill existing bacteria from infected roots remaining in the soil. Heat is the only effective method of soil pasteurization.
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