About Crown Gall

• Crown gall is a disease that is caused by the bacterium Agroacterium tumefaciens and that is known to infect hundreds of plant species. The bacteria that causes this disease enters the plant through wounds in the roots, trunk or branches. As the disease infects the plant, it prevents the shrub or tree from being able to absorb and transport necessary nutrients from the soil, and this can severely debilitate or kill the host.
  
  

Symptoms

• Because the bacteria that causes crown gall is present in the soil, the first signs of infection usually appear in close proximity to the soil line. As crown gall infects its host, it create a growth or a tumor at the point of infection. This growth first appears white in color and is soft to the touch, but as the disease progresses, it become hard and darker in color. Depending upon the severity of the infection, these tumors can range in size from the size of a pea up to one foot in diameter. In severe cases, these tumors will eventually cause the discoloration and defoliation of the plant, which can lead to the death of the host.
  
  

Life Cycle

• The bacteria that causes crown gall resides in the soil, where it is capable of surviving for up to 10 years. This disease can be spread through a variety of methods, including by animals, irrigation or rain splash. Wounds in the root, trunk or branches of the tree that have been caused by insects, and damage done by mowing, or through the planting or pruning process, act as access points for this bacteria to infect the flesh of the plant. When the tumors fall back to the soil, they reinfect the soil with the bacteria and make it possible for this disease to reinfect new growth.
  
  

Prevention

• The best form of prevention is to plant species that are resistant to crown gall disease. Plants that have not yet become infected should be cared for properly to avoid wounds that would act as an entrance point for the bacterium. If you have removed a plant that has become infected, do not plant another plant in the same soil that is known to be susceptible to crown gall disease. When planting new plants, inspect the seedlings for any sign of the disease before planting the species in your landscape.
  
  

Control

• If signs of infection have already been detected, prune and dispose of infected areas, being careful to sterilize the shears between every cut to prevent the spread of the disease. Apply pesticides and insecticides to prevent pests from damaging the plant and causing wounds in the plant.