Q: What is this big growth on my euonymus plant?

Paula from Canfield

A: We really appreciate the sample, it helps us ensure we are providing the best answer possible for your question.

What’s growing on your euonymus is a type of gall called a crown gall. Galls are made of plant tissue, the growth of which has been taken over by an invading organism, insect, mite, fungus, or a bacterium for the invaders benefit. Typically, the invading organism releases a chemical that hijacks the plant’s normal growth processes producing the growths you see. Most galls don’t harm their host plant. Crown gall is one of the few exceptions to this rule. Crown galls stunt the growth and disfigure the plants they infect. If a grown gall is on the main stem of a younger plant, it can kill it.

Crown gall is caused by a soilborne bacterium, Agrobacterium tumefaciens, that enters a plant through wounds to its stems or roots. After the bacteria enters a plant, it inserts some of its DNA into the plant’s DNA. This causes an over production of a plant growth hormone that creates the gall. Once the bacterium is in a plant, nothing can be done to stop it. Crown galls infect many other plants besides euonymus. In fact, Wisconsin extensions report that crown gall is the most widely distributed bacterial disease in the world, infecting hundreds of plant species worldwide.

The galls begin as light colored, soft growths and turn dark and woody as they age. Crown galls can be large, up to several inches in diameter. Crown galls are commonly found on stems and roots usually near the soil line. The galls on stems and roots interfere with the plant’s vascular tissue that transports water and nutrients, stunting plant growth. Pruning out galls will temporarily improve the appearance of the plant but won’t stop the disease.

So, what can be done about crown gall? Prevention is the best protection. Before purchasing or installing a plant, inspect the stems and roots for galls.

Avoid cutting the plant; a cut is a primary source of entry for the bacteria. Practice good sanitation; clean tools with a disinfectant, such as a 10 percent bleach solution or rubbing alcohol.

If your plant already has this disease, remove and destroy it (don’t compost it). The galls on the plant will shed the bacteria into the soil where they can remain for years. Dig out and remove as much of the roots and surrounding soil as you can.

For pictures and more details, go to http://go.osu.edu/crowngall.

Today’s answer is provided by David Sprague, OSU Extension Master Gardner Volunteer. Our Plant and Pest Clinic is open for help with plant issues, soil testing and insect identification, 9 a.m. to noon Mondays and Wednesdays. Questions be submitted at any time. For details, go to go.osu.edu/mahoningclinic.