Oak Wilt is a vascular disease of oak trees caused by a fungus. The fungus enters the tree and stops the flow of water and elements by plugging the vessels inthe vascular systems. The disease is most serious on members of the red oak family, though it can affect many other members of the oak family. Once a red oak becomes infected with the oak wilt fungus, it usually dies within several months.This introduced vascular wilt fungus is mostly transmitted by insects and through root grafts. The most common predisposing factors for trees are injury and human activity being the leading causes of infection.
Oak wilt moves slowly on its own through root systems and travels short distances overland when new spores of the fungus are moved by beetles from an infected tree to a freshly pruned or injured tree. The disease also spreads, killing nearby oaks from one year to the next.
Symptoms in oak trees recently infected includes the following:
- Leaf margin browning progressing inward from the leaf tips to the leaf bases.
- Leaves on branches may appear to be wilting.
- Fungal mats may develop beneath the bark.
Look for oaks that suddenly drop their leaves in summer, or have obvious decline in leaf health during the growing season.
The health of oaks becomes high risk during the warm season months when they are injured through human practices, especially pruning, and through storm damage. Several species of beetles are attracted to the fresh wounds caused by trimmingand storm damage. The beetle’s activity can act as a vector and can transmit the fungus to healthy, recently pruned or damaged oak trees. Trees which come into contact with the fungus in the spring are often dead by August or September.
- DO NOT prune oak trees during the growing season
- DO NOT move firewood
Oak wilt is spread by the movement of infected wood and the pruning of oaks during the summer months.
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