Oak branch dieback
Diplodia quercina
What is Oak branch dieback (Diplodia quercina)?
Diplodia quercina and Diplodia corticola are fungi that cause branch canker and dieback in oak trees. They primarily affect oak species such as California black oak, coast live oak, English oak, and valley oak. Symptoms include complete branch death, browning, wilting, and the presence of black fruiting bodies (pycnidia) on the bark. Diplodia quercina leads to the death of small branches (<1-4 inches in diameter), resulting in brown, wilted leaves remaining in the canopy. Outbreaks of oak branch dieback often follow periods of below-average rainfall.
How does Oak branch dieback (Diplodia quercina) occur?
Diplodia spp. diseases are characterized by the presence of small, black, raised fruiting bodies (pycnidia) on the bark of infected trees. The fungi enter branches through wounds or natural openings. The fungi cause branch canker and dieback, resulting in symptoms and the presence of black fruiting bodies. These diseases often emerge following periods of below-average rainfall. The fungi spread through spore production from fruiting bodies and can continue releasing spores for up to two years.
Symptoms
1 - Plants Health
• Diplodia quercina fungi cause branch death, browning, wilting, and the presence of dead leaves in oak trees. Infected trees may also show signs of crown thinning, pale leaves, and bark bleeding. • These symptoms contribute to the overall decline and weakening of the tree, leading to potential long-term damage and reduced vitality.
2 - Soil Health
Diplodia quercina impacts soil by providing organic matter through decomposing dead branches and leaves. Loss of branches and canopy decreases shade, wildlife habitat, and food sources.
Solutions
1 - Prevention Measures
• Maintain overall tree health through proper cultural care, including adequate watering, pruning, and fertilization. • Monitor and address any underlying issues that may weaken the trees, such as nutrient deficiencies or other diseases. • Prevent unnecessary wounds to tree branches and trunks, as wounds provide entry points for fungi. • Mitigate environmental stress factors such as drought and extreme temperature fluctuations. • Remove and destroy infected plant material to prevent the spread of the disease.
