Euonymus-Crown Gall

Cause Rhizobium radiobacter (formerly Agrobacterium tumefaciens), a soilborne bacterium, enters Euonymus plants through wounds, either natural or caused by pruning, grafting, mechanical injury from cultivation, heaving of frozen soils, chewing insects, or the emergence of lateral roots. After the bacterium enters a wound, a small piece of its DNA is transferred into the plant's DNA. The foreign DNA transforms normal plant cells in the wounded area into tumor cells. Once transformed, tumor cells proliferate automatically. The result is a gall, a disorganized mass of hyperplastic and hypertrophic tissue.

Symptoms Large, fleshy galls occur on roots and anywhere along aerial shoots and branches. These aboveground galls are white to greenish at first and firm like cauliflower but become hard and dark brown with age. Infected plants may be stunted, lack normal green color, and die back during severe winters. Symptoms may not develop for over a year if infection occurs when temperatures are below 59°F.

Cultural control

  • Destroy heavily infected plants.
  • If infections are few, prune off galls. Sterilize pruners between cuts.
  • Prevent wounding as much as possible.
  • Do not take cuttings from diseased plants.

Chemical control

  • Gallex (ready to use) painted on very young galls to reduce further development. Galls may return the following year or, if treated late, may continue to develop. Tissue surrounding the gall may be injured, especially on younger plants. Prepare the surface by removing soil from around the galled area, and allow the area to dry before application. Not registered in Idaho. 24-hr reentry.

Biological control Soak cuttings or plants into a suspension of A. radiobacter strain 84. To be effective it must be applied a few hours after wounding. Change solution frequently because if a set of plants contaminated with other pathogens is dipped then all succeeding plants dipped into the same container/solution will become contaminated.

  • Galltrol-A (Agrobacterium radiobacter K84). Not registered in Idaho. 12-hr reentry. O
  • NOGALL at 8.8 oz/2.5 gal unchlorinated water per 2,500 nonbearing plants. Apply within 2 hours of lifting and/or damaging plants. Do not use with any pesticides or fertilizers. 4-hr reentry. O

Reference Penyalver, R., Vicedo, B., and López, M.M. 2000. Use of the genetically engineered Agrobacterium strain K1026 for biological control of crown gall. European Journal of Plant Pathology 106: 801-810.