Plant Lady: Pathogens cause galls on woody plants

Can you identify what is wrong with these plants?

Debbie Pell

New Smyrna Beach

You have a terrific specimen of Sphaeropsis tumefaciens or Sphaeropsis gall on the bottle brush. This is a fungus that is associated with citrus (although infrequently), Carissa spp. (natal plumb), oleander, holly, Brazilian pepper and eucalyptus.

According to the University of Florida, control involves pruning out branches well below gall areas and destroying infected branches. Pruning tools should be dipped in a disinfectant such as 10 percent household bleach before each cut. Pruning wounds on the branches should be treated with protective paint. Humid weather and wet foliage are needed for spore germination and infection to occur. Apparently, infection does not require wounds, but older shoots and branches can become infected through wounds or cuts from various causes. Some studies have shown that young foliage can be infected without wounding. Some varieties of hollies and bottle brush are more susceptible than others. Unfortunately, no chemical fungicides are available to control this fungus.

What you have on the Knock Out rose (not pictured) is crown gall caused by Agrobacterium tumefaciens, which enters the plant through wounds made during grafting, planting, pruning or insect feeding. Often, plants are infected in the nursery and the disease develops later, after planting in the garden. Symptoms are a gradual decline in plant health, often associated with the presence of spherical, woody growths at the crown or on stems. Galls have rough surfaces and may grow up to 6 inches in diameter (yours is measured at 3.75 inches now!). Diseased plants should be removed and destroyed.

According to the literature, it is found on many hosts and has a unique biology. Basically, the bacterium transfers part of its DNA to the plant, and this DNA integrates into the plant’s genome, causing the production of tumors and associated changes in plant metabolism. Fantastic specimen! Looks like the roundworms love it too!