Fungicides applied in the course of the regular scab spray program will control powdery mildew. The bacteria transform normal plant cells into tumor cells, which become wart-like growths of disorganized tissues. Initially, the tumorous growths can be confused with callus tissue, but later they become round, rough and dark. The bacteria can survive in the soil for several years. They enter pecan roots or stems near the soil line through wounds often caused by insects, grafting and cultivation.
Galls reduce tree vigor by retarding the flow of water and nutrients in the vascular tissue.
The external portions of the galls deteriorate from lack of water and slough off. These tissues often contain the bacteria and reintroduce them into the soil. Crown gall is controlled through preventive cultural and sanitation practices. Only healthy, vigorous, disease-free trees should be planted. Take care during transplanting not to wound the roots and trunks.