Crown gall—Agrobacterium tumefaciens
The crown gall bacteria cause galls principally on the root
crown at the soil line or just below the soil surface. Galls
sometimes also form on roots, limbs, and trunks of many woody
plants. Crown gall usually
does not seriously harm woody plants unless galls occur in
the root crown area when plants are young; then plants become
stunted and subject to wind damage and drought stress. If
galls are large, young plants
can be girdled and killed. Agrobacterium tumefaciens causes
crown gall on fruit trees, euonymus, rose, willow, and other
broadleaf trees and shrubs. Another bacteria, possibly Agrobacterium
pseudotsugae, causes a similar bacterial gall on stems
of douglas-fir, especially under wet stressed conditions.
Identification | Life
cycle
Solutions
Purchase and plant only high-quality nursery stock. Avoid injuring trees during transplanting. Solarization during the hot dry season before planting may reduce crown gall bacteria in the soil. Where crown gall
has been a problem, plant only resistant species, including birch, cedar, magnolia, pine, redwood, and
tulip tree. Existing galls may be excised by cutting into healthy wood around galls, then exposing the
tissue to drying. Cut out galls only during the dry season and minimize the amount of healthy tissue into
which cuts are made. | 
Swollen outgrowths found on stem
Galls on roots
|
