Crown Gall...Certainly Not Royal, Even If It Is Extremely Galling

You may have seen it and not known what it was.  I noticed what looked like a gnarled lump of old wood on the trunk of my Chinese wisteria (Wisteria sinesis) just above the soil level.   It was so interesting.  It seemed to have come from nowhere and was about the size of my fist.  I hadn’t seen it start and I didn’t notice it as it grew.  I watched and wondered for a few months ... maybe for too many months if my delay caused its tragic fate to be sealed.

I had heard of crown gall (Agrobacterium tumefaciens) and considered the possibility but my mature wisteria had never looked better than it did last spring and summer.  Besides, crown gall is a pathogenic tumor with possible outcomes so dire, so negative; I didn’t want to believe the bad news.  This wisteria grows on a little old out building at the back of my yard with my vegetable plot at its feet.  I love it.

Two days ago on one of my frequent checks, I stopped in my tracks.  Directly above me where a sturdy stem came out from the trunk was another gall.  Perhaps I waited too long to decide what to do.

Crown gall is not only a disease often deadly to the host plant, its pathogens essentially poison the surrounding soil.   Gardeners are advised not to plant anything in the area for up to two years- not good news for my vegetable garden.

Some sources advise against cutting off the gall because the bacteria can spread.  I cut off the stem on the newer one and put it in some water with a little bleach.  That recourse was not possible with the one on the trunk so I followed the UCD IPM advice to cut into healthy wood around a gall, then let the tissue dry.  I cut the gall out of the trunk and put it in the bleach solution.  The shears went into the bleach also.  I was determined not to infect anything else!

So here’s a possible silver lining.  In order to be poisonous, the bacterium must contain certain tumor inducing properties and genes necessary to transfer it to the plant cell.  Many strains of the bacteria are not able to do this.

I’m counting on the possibility that my wisteria has one of them.

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