Oak leaves browning or dropping in a St. Louis summer

What might be happening?

The Missouri Department of Conservation describes browning and wilting in the upper crown of red oaks and scattered affected branches in white oaks. It stresses that an accurate diagnosis is essential because other disorders can resemble oak wilt.[7]

What to tell the arborist

Note how quickly symptoms are spreading, which part of the tree changed first and whether nearby oaks look different. Tell us about pruning or storm wounds. Do not cut a sample yourself; ask how appropriate diagnostic material should be collected.

The next step

Have the arborist assess the tree and discuss laboratory confirmation where needed. Protecting nearby trees, managing affected wood and deciding whether an individual tree can stay are different decisions.

What not to assume

Do not assume an injection cures advanced wilt. MDC describes preventive fungicide use before symptoms, not a rescue guarantee for a severely affected red oak.[7] MU Extension recommends winter oak pruning to avoid the high-risk mid-March through mid-July period.[2]

Sources

• [7] Missouri Department of Conservation: oak wilt
• [2] MU Extension: winter oak pruning