How To: Identify Crown Gall

img 0268 300x248 How To: Identify Crown GallLooking over some garden hedges recently, I discovered a type of gall on all six of the identical shrubs. The gall growths were hard, irregularly shaped, and about two inches in diameter. I looked over the area that the galls were attached to, and noticed that the galls were mostly growing in areas that had been pruned within the last one or two years, a sign that pointed to a bacterial gall instead of an insect gall.  I snapped the gall off of the plant to have a closer look.

There are many types of gall with several specific causes, but they can generally be broken down into two categories: disease caused, and insect caused.  Insect caused galls come in all shapes and sizes, both soft tissue growths, fuzzy growths, and firm growths. All of them hold either the eggs or larvae of a specific type of wasp or mite inside, and can contain hollow areas inside the gall where the creature lives and feeds.  Insect caused galls may look strange and detract from the outward appearance of a plant, but they do not damage plants. Disease galls do damage a plant, and are initially caused by a bacterium that lives in the soil, although they are commonly spread from plant to plant by pruning, or grafting, when hedge shears have come into contact with an infected plant. The true damage caused by a bacterial gall is actually in and around the gall growth, where the unchecked growth of cell tissue distorts, or chokes off the flow of water and nutrients through the plant.

How To Discern Between Insect And Disease Caused Galls:

With the above pictured gall, I investigated the cause of the growth visually from the exterior appearance, and by dissecting the growth, to check for hollow areas inside the gall that would be a sign of insects.  I found that the gall was solid throughout, with layers of disorganized tissue, and concluded that the gall was in fact Crown Gall, a bacterial infection. If you find a gall on one of your plants you will need to do these two things to determine the root cause. Identifying the shape of a gall is important, the shape and appearance of a gall can most often tell you what the root cause is. If you are unsure, or just curious, you can then dissect the gall to check the inside for insect life.

Diagnosing The Problem And Finding A Solution:

The gall effecting the shrub photographed above was determined to be Crown Gall. Crown Gall is a firm, crusty growth, that most commonly effects types of Euonymous, Roses, and fruit trees.  It is caused by a bacterial infection that occurs in some soil, causing the plants cells to divided radically, and tumor like, forming continually growing lumps, that are irregular in shape.

The most commonly given advice regarding Crown Gall calls for the removal and bagging of infected shrubs, including some of the soil from around the plant.  These methods often request that either disease resistant shrubs are planted in place of the old ones, or that the area is allowed to remain fallow for up to 2 years (planted with grass), to eradicate the disease from the soil. The other alternative, for those who want to try and save their plant first, is to trim off any gall growths, and to coat the fresh cut with tree surgeons paint, or there are experimental methods being researched involving hot water, and others involving tree surgery, disinfection, and direct heat application.

There is no market cure for the treatment of this disease, and the easiest way to prevent the spread of it is simply through the entire removal of the problem shrub.  In either circumstance, any tools that come into contact with the infected plant should be cleaned with rubbing alcohol, to prevent further infection in other garden plants.

My Thoughts: In this circumstance, the homeowner was willing to try experimental treatments, so we will proceed down that road to see what results we can encourage.  If any of the experimental methods of control work I will post about them at a later date.

Your Thoughts:  Have you had trouble with this type of gall? Have you removed the infected plant all together, or have you tried other methods of control?  Have you had any luck with alternative methods of Crown Gall control?

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  1. Please send me a picture (high quality) about crown gall tumor.


    Dr. M. R. Hadi


  1. [...] of the existing garden residents gets to stay.  We found out last year that our bushes had a bacterial infection called crown gall and needed to be removed.  Aside from those bushes – which had been designated “anchors” of [...]

  2. [...] crown gall, an incurable disease that attacks some types of plants (see Green Gardenista’s article on identifying crown gall for more [...]

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