Leafy gall is a disease caused by the bacterium Rhodococcus fascians, which enters the plant through wounds in roots or stems and stimulates the plant tissues to grow in a disorganised way, producing dense clusters of distorted, leafy shoots.

The disease is not common and seldom damaging. In gardens, Chrysanthemum, Dahlia, Lathyrus (sweet pea), Nicotiana, Pelargonium (geranium) and strawberries are among the plants most commonly attacked.  Expect to see this disease in summer.

You may see the following symptoms:

• dense clusters of distorted leafy shoots, often close to ground level
• witches' broom
• bud proliferation
• reduced lateral root development
• flattened stems (fasciation) - less common, and this symptom can have several other causes

Non-chemical control

Leafy gall is seldom serious enough to warrant control, but if it is troublesome, carefully sterilise pots, surfaces and tools to help eliminate the causal bacterium, Rhodococcus fascians. All potentially-contaminated growing media (potting compost) should be destroyed (or sent for council composting).

Chemical control

There are no chemicals available for the control of leafy gall.

Infection by Rhodococcus fascians (formerly Corynebacterium fascians) has a similar effect to that of crown gall, another bacterial disease, but instead of galls the host tissues produce dense clusters of distorted, stunted shoots at ground level. The bacterium disrupts normal plant hormone levels, in particular auxins and cytokinins, causing the symptoms observed.