About

• Fungal gummosis is a fungus that affects peach trees. It initially appears as blisters on the bark, which eventually develop into strips of necrotic tissue. As the disease progresses, the bark becomes darker, decays, and peels. Fungal gummosis can overtake entire branches, repeatedly reinfecting them in areas where bark has peeled until the branch is dead and tree's overall health is compromised.
  
  

Detection

• Fungal gummosis can be first diagnosed from the black blisters that appear on young bark. Lenticels are typically visible at the center of blisters. Symptoms are identifiable on trees late in the season when the infection happens, or the next spring. Often at the culmination of the second spring, the tissue surrounding the blisters has expanded and a dark residue is secreted. Near the final stages of the initial infection, the bark peels. Unless the tree is treated, the fungus continues to reinfect the tree and produce new blisters.
  
  

Impact

• Stressed trees are more prone than healthy ones to fungal infections. Trees without proper irrigation are also susceptible. Moreover, weak trees are more affected by the fungus and usually die sooner than healthy trees that become infected. Under the right growing conditions, peach trees that encounter the fungus can fight it off by developing a cork layer under the infected area. The tree naturally sheds the top layer, where the infection exists, and significant damage to the tree's integrity is usually avoided.
  
  

Control

• Remove decayed branches in the winter, and destroy them. Avoid pruning your peach tree in the summer, when it is prone to wounds that serve as entry points for the fungus to invade the tree. Apply a fungicide, such as captan, each week during May and July, when the threat of fungal infection is greatest. Plant disease-resistant peach trees whenever possible.