What is crown gall?
Crown gall is a bacterial disease of world-wide importance on many woody plants. It can be especially serious in nurseries growing susceptible ornamental plants and deciduous fruit trees.
Crown gall is caused by the bacterium Agrobacterium tumefaciens and is a disease which causes hard woody galls on plant roots and stems. The galls have a rough convoluted surface. They vary in size, often growing many times larger than the diameter of the roots or stems. Some galls reach over 60 cm in diameter on old trees.
Crown gall is mainly considered a nursery problem. Open ground nursery plants need to be lifted exposing the galls whereas the roots of orchard trees are not usually examined after planting.
Gall formation can disrupt the plant’s food and water conducting tissue causing infected young plants to become stunned and grow poorly. On older trees the galls can also serve as entry points for secondary wood rots which weaken the trees.
The biological answer
When Dygall® directions on the label are followed, this material should provide a safe, natural and inexpensive but efficient, method of preventing a troublesome disease on many susceptible plants by simply immersing plants in a suspension of Dygall® and nature takes its course. It is important to remember that Dygall® is a preventative for crown gall and should be applied to susceptible plants before exposure to the disease or final field placements as it will not control existing infections.
Soil treatment with steam or methyl bromide-chloropicrin mixture can be effective but only if all the crown gall bacteria are destroyed. A small residue of these pathogenic organisms can multiply rapidly and expensive soil treatment does not always provide the degree of control required. However, it is now possible for nurserymen and horticulturists to control crown gall by simply inoculating seedlings, cuttings, peach stones etc., with Dygall® prior to planting.
Dygall® is produced under stringent quality control procedures and supplied in 106g packs each containing approximately 5000 million viable bacteria per gram. Unopened packs can be cool stored if required until the expiry date shown. Dygall® is highly effective – one pack is sufficient to inoculate up to 7500 rose cuttings, 2500-7500 rooted cuttings of plum, euonymus, raspberry, etc., (depending on size of root systems) and up to 10,000 peach seeds.