"galls" caused by bacteria is usually not correct, since tecnically they are no true galls, although they look like galls. Very confusing!! They are described in many books on galls, because of the similar morphology. Many gall causers cause cancerous like growth. But, with bacteria growth still continues when the bacteria are removed from the "gall". By pure definition of what is a gall the galformation should stop at the moment the gall maker is absent!

It happens that plants die because of the presence of "galls", but sometimes the bacteria are working together with their host, in a symbiotic proces (for example nitrogen fixatie in exchange for nutrients in the generea Frankia and Rhizobium). The nice thiing about galls that are caused by bacteria is that is hard to tell the difference between actuall galls and growth as a reaction to damage to the host plant. The best known genera are Agrobacterium and Pseudomonas.

Agrobacterium tumefaciens can be found on many many plant species. Which does not mean the pictures on the right are all growths caused by this species. The "galls" can be found on trunks, branches, roots, stems and leaves.

In the Netherlands the "galls" are known from root and stem growth on roses, and from very large growths on the roots of Chamaecyparis lawsoniana, like on one of the bottom pictures on this page on the cultivar 'Alumii'.


Picture: J. Wolfs
Betula pendula

Picture: H. Strijbosch
Betula pendula

Picture's: R. Nijboer
Ulmus minor 'Sarniensis'

Picture: W. van der Ven
Chamaecyparis lawsoniana 'Alumii'

Picture: Harry Holsteijn