Branch Canker and Dieback

The first sign of branch canker and dieback is reddish sap that dries to a white powder. If you grow avocados or pears, you should know what else to look for and how to respond.
 
Formerly known as Dothiorella canker, this fungal disease is caused by several different fungi. Most are in the Diplodia genus, along with Kalmusia variispora, Eutypa lata, and Neofusicoccum parvum.
 
Symptoms of branch canker and dieback
 
Identifying the problem is your first step in saving your trees. Unfortunately, I couldn’t find any usable images. Symptoms of branch canker and dieback include the following:
 

• Branch cankers
• Cracked, discolored, or sunken bark
• Dead spurs
• Dieback above the graft union
• Leaf flagging
• Leaf scorch
• Pruning wound lesions
• Reddish brown to brown inner bark
• Shoot blight
• Stem end fruit rot
• Swollen graft unions

 
Leaf flagging refers to leaves that die quickly but remain attached to the tree.
 
If you cut off an infected branch, you will see a wedge-shaped canker that reaches the xylem. In branch canker and dieback, these discolored areas can penetrate deeply into the wood, allowing fungal spores to spread into other parts of the tree. Phytophthora trunk cankers are more shallow. That said, many trees can live with branch canker and dieback, while Phytophthora trunk canker is a more serious disease.
 
Older trees may be able to withstand a branch canker and dieback infection, but young trees often cannot. If the disease girdles the main trunk, it can kill mature trees.
 
Branch canker and dieback often takes hold after a tree has been damaged by fire blight, sunburn, or sloppy pruning. Clean cuts and sharp tools help keep your trees healthy. Trees suffering from nutrient deficiencies, drought, improper irrigation, and insect and mite feeding are also more likely to become infected. Fungal spores travel on breezes and in rain and irrigation splashes.
 
Managing branch canker and dieback
 
Good cultural practices, sanitation, and investing in certified pest- and disease-free bare root stock and other plants are the best ways to prevent branch canker and dieback. Once the disease occurs, use the following tips to minimize its effects:
 

• Prune out infected twigs and branches, cleaning your cutting tools with disinfectant between each cut to prevent further infection.
• Discard infected plant material in the trash.
• Only work with your trees when they are dry.
• Do not allow sprinkler spray to hit tree trunks.

 
Get outside and take a closer look at your trees. The more familiar you are with them, the more quickly you can spot and respond to problems.
 
Walking among trees, out in nature, is a good way to take care of yourself, too.