What Is Crown Gall?

Crown gall is a bacterial plant disease that can reduce plant vigour and cause losses in nurseries, orchards, and vineyards. This page explains the basics and the prevention-first approach.

What causes crown gall disease?

Crown gall is most commonly associated with Agrobacterium tumefaciens, a soil-borne bacterium that can enter plants through fresh wounds. Wounds can be caused during propagation, planting, grafting, pruning, and handling.

Once infection occurs, the bacterium can trigger abnormal growth that forms rough, woody galls, often near the crown (the junction between roots and stem). These galls can interfere with water and nutrient movement, especially in young plants.

What does crown gall look like?

Early galls may appear as small, light-coloured swellings. Over time they can become larger, darker, and woody. In nurseries, galls are often observed on roots, at the soil line, or on lower stems.

Because symptoms can vary by host plant and growing conditions, it’s important to combine visual scouting with good production records and sanitation practices.

Crown gall growth near the plant crown — Crown gall on wine grape

Which crops and plants are affected?

Crown gall can affect a wide range of woody plants and horticultural crops. Examples include:

Grapevines
Roses and woody ornamentals
Stone fruits (e.g., cherry, peach, plum)
Pome fruits (e.g., apple, pear)
Small fruits and berries (e.g., raspberry, blueberry)

In Canadian nurseries and orchards, the disease is a practical management issue because young stock is most vulnerable and infections can be introduced during propagation and planting.

How does crown gall spread?

The bacterium can persist in soil and plant debris. It typically spreads when contaminated soil or water contacts wounds, or when infected plant material is moved between sites.

Common risk factors include:

Planting into infested ground
Mechanical injury during handling or transplanting
Grafting or pruning without proper tool sanitation
Re-using contaminated pots, benches, or propagation equipment

Prevention and biological control

Crown gall management is strongest when focused on prevention. This includes nursery sanitation, careful handling to reduce wounding, and preventative biological control where appropriate.