Eutypa Dieback and Bot Canker

Eutypa dieback, gummosis, and limb dieback, causes limbs or twigs to wilt and die suddenly in late spring or summer with the leaves still attached. The bark has a dark discoloration with amber-colored gumming; infected xylem tissue and cambium are discolored brown.

Disease organisms infect fresh pruning wounds in the fall and winter when pruning occurs during, or just before, rainfall. While new infections caused by Eutypa only occur during fall and winter rainfall, Botryospaeria species may infect during a spring or summer pruning followed by irrigation. It may also seem as if new infections have occured after spring pruning if this pruning did not remove all the previously infected wood.

Remove infected limbs at least 1 foot below any internal symptom of the disease. The preferred control method is to prune during July and August after harvest. There is less regrowth from pruning cuts if pruning is done in August. Ideally, pruning should be completed at least 6 weeks before the first fall rains. Treating wounds with paints or sealants has not been satisfactory due to the lack of long-term efficacy of these products or the difficulty in treating all pruning wounds immediately after they are made. If pruning wounds are made outside of the preferred pruning period of July through August, use a fungicide to treat the wounds.