Galls are not hard, but soft and spongy. The centers of older galls decay. They enter only through wounds.
Crown gall is most damaging to young trees, either in the nursery or in new plantings.
Galltrol and Norbac are preparations of the biological control agent Agrobacterium K-84, which is effective only as a preventive treatment and is used as a root dip prior to heeling in or planting. It does not eradicate existing galls. Strains of A. tumefaciens resistant to Galltrol and Norbac have been reported. Their occurrence is not widespread, but failure to control crown gall with these materials should be reported. Eradication of existing galls involves removal of the gall and topical application of Gallex.