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The gall of some bacteria

By Ralph E. Mitchell

One problem of roses, and hundreds of other plants, is a disease called crown gall.  It is caused by a bacterial disease that produces tumor-like growths on the stem of the plant near the soil level.  Sometimes an ailment of roses, crown gall needs to be recognized and managed before it gets out of hand.

There are few rose growers who have not suffered from crown gall at one time in their career.  The bacteria involved can live in the soil for nearly three years continuing to infect plants installed nearby.  This bacteria must enter a wound of some type – a freeze-crack, via a contaminated pruning tool, insects, or even microscopic nematodes.  This organism enters the plant cells and causes the tissue to swell and the gall to begin to form in as early as fourteen days.   Some infections are much slower to manifest as galls and could take up to six months to develop.  The eventual gall can grow from pea to baseball-size over time.  The gall is initially light brown in color, but darkens with age to a blackish hue.  The gall eventually disfigures the plant and often girdles the stem.

If you find your rose has a crown gall, the best remedy is to pull the rose out and destroy it.  It is not going to get any better and is very infectious to other roses.  Gall removal attempts only move the infective material around and can cause additional infections.  Plant only disease-free roses right from the get-go.  For that matter, do not plant roses in soil with a history of crown galls for at least three years as additional infections are likely.  Planting locations noted for a heavy presence of nematodes and root-feeding insects should be avoided.  Keep your cleaning tools disinfected.  Use a ten percent bleach solution or quaternary ammonium-based disinfectants to clean pruning tools.  This is a good horticultural practice across the board.

While finding a crown gall can be discouraging, knowing what to do next can help prevent further infections and minimize an outbreak.  For more information on all types of plant diseases and how to manage them, please call our Master Gardener volunteers on the Plant Lifeline on Mondays, Wednesdays and Fridays from 1 to 4 pm at 764-4340 for gardening help and insight into their role as an Extension volunteer.  Don’t forget to visit our other County Plant Clinics in the area.  Please check this link for a complete list of site locations, dates and times – http://blogs.ifas.ufl.edu/charlotteco/files/2018/03/Plant-Clinics-Schedule.pdf.     Ralph E. Mitchell is the Director/Horticulture Agent for the Charlotte County Extension Service. He can be reached at 941-764-4344 or ralph.mitchell@charlottecountyfl.gov.

Resource:
Duman, K., da Silva, S., Iriarte, F., Riddle, B.,  Knox, G.,  Orwat, M., Steed, S.,  Compoverde, E. V.,  Jones, J., & Paret, M..   (2018) Bacterial Crown Gall of Roses Caused by Agrobacterium
Tumefaciens.  The University of Florida Extension Service, IFAS.

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