Key Features
- Wilt, chlorosis or dieback
- Sunken or blistered cankers
- Symptoms on a one or a few branches
Symptoms
Wilting is the first symptom observed, followed by scattered dieback in new growth branches tips. Leaves on affected branches wilt as branches die. Thin barked trees often develop blisters. Sap producers, such as ornamental Prunus species or sweet-gum, produce excrete large amounts of sap which accumulates on the branch. Rough, sunken, dark-brown to black cankers form around wounds or natural openings in the bark and are found below blight blight symptoms. Cutting into infected branches reveals blackened wood and pith. Cankers enlarge along the branch but do not alway girdle the branch. In older, infected tissue, dead bark may crack and fall off the canker. Small black fruiting bodies may form in the within and on the edges of cankers. Microscopic analysis of the fruiting bodies is required for a conclusive diagnosis. Contact a plant disease diagnostic lab for more information on submitting cankers samples for analysis.
Biology
The fungus overwinters in cankers formed the previous growing season. In the spring, wet weather stimulates black fruiting bodies, embedded in the wood or bark, to produce spores. Spores are spread by wind, water, insects, and contaminated pruning tools. Botryosphaeria enters a new host through natural openings in the bark, such as lenticels or insect damage or through pruning cuts, and wounds. Following infection, the fungus grows through the plant tissues just beneath the bark causing sunken cankers. Injured, wounded, or stressed plants are most susceptible to this disease.
Management Recommendations
Reduce the risk of infection by reducing stresses caused by the many environmental factors that make trees more susceptible to Botryosphaeria fungi. These factors include drought, freezing, soil compaction and high soil pH. Prune to remove cankered branches after fall leaf drop or before buds break in the spring. Disinfest pruning tools between cuts with a 10% bleach solution for 10 minutes and rinsing or by dipping them in 70% alcohol and letting them air-dry. Destroy the infected tissue. No fungicides have been shown to be effective against this disease.
Effective Pesticides
Pesticides are neither available nor recommended for managing this disease.
Resources
