One of Innsbrook’s property owners recently contacted our Director of Horticulture, Keith Thompson, concerned about signs of oak tree decline they’ve noticed around their property and other areas of the Innsbrook forest.

The Missouri Department of Conservation provides us this information on the importance of the oak tree to the forest ecology: In the history of just one old oak tree, thousands of creatures influence, and are influenced by, its growth. In summer, many animals feast on oak leaves. June beetles chew circular holes in the leaves at night. Walkingsticks consume entire leaves, leaving only the veins. Many kinds of caterpillars eat oak leaves. All of these insects, in turn, become food for birds, snakes, lizards and bats. The acorns of the oaks are the main winter food for deer, turkey, jays and squirrels.

Oaks also provide shelter for wildlife. Chipmunks can live among the roots of the tree. Squirrels build spherical nests of leaves and twigs in the branches or find shelter in tree cavities. Many bird species nest in oaks, including jays, warblers, tanagers and woodpeckers. No wonder this property owner is concerned about the possibility of losing these important trees!

“Last summer, the number of trees on our property and surrounding properties with sparse foliage was alarming,” said the property owner. “We have lost a significant number of oak trees on our property. I [also] see dead trees as I walk the roads.”

We thought the information Keith provided would be beneficial to others in Innsbrook and the rest of Missouri, so we sat down with him for a Q-and-A.

Keith Thompson.

Has Innsbrook ever surveyed to determine how serious the oak decline is?
“We have not done a detailed assessment – I rely on information from the Missouri Department of Conservation, U.S. Forest Service, Innsbrook property owners and my own experience as I travel around the development. I do not believe we have an issue past the typical decline of oaks due to environmental stresses, including drought (especially the severe drought and extreme temperatures experienced 3 – 4 years ago).

“There was a year when our area experienced a quick hail storm just before Memorial Day weekend, which defoliated approximately 40-50 percent of the forest canopy. This was an extreme stressor. With reduced leaf canopy, trees had difficulty producing more sugars through photosynthesis. This one stress event impacted our forest for a good decade.”

Pockets of oak mortality resulting from the interaction of stress, insects, diseases and site factors (photo was not taken at Innsbrook).

Are there any specific stress factors unique to Innsbrook beyond the general problems of drought?
“Stress factors vary by ecological location (rocky glade, ridge top, valley, etc.), environmental/weather impacts, fire, previous logging/management practices, construction of buildings and roads, and individual property owner practices and management. But, no, Innsbrook’s forest is not experiencing any unique factors of stress. There is no elevated presence of pests (insect, disease, or fungal) in relationship to our forest.”

Is there offensive action to take if there is a specific stress factor in addition to drought?
“What should be understood is forest management is a whole different animal compared to urban forestry. In a St. Louis neighborhood with limited trees and vegetation, a disconnected/void diverse ecosystem, and for the most part a monoculture – when a tree or shrub is performing poorly and showing some indication of stress, homeowners will usually notice quickly and take some type of corrective measure. It is also easier to isolate, treat or eradicate a pest in this type of environment.

“In the forest, a primary pathogen is Armillaria mellea – a decay-type fungus that aids in breaking down dead woody material and turning a dead tree, stump or roots into a beneficial food source for insects. Insects are eaten by numerous animals, etc. and as the deadwood continues to decay, nutrients are returned to the soil for the next generation of trees and vegetation.

“Now, the downside is – Armillaria mellea also can infect stress-weakened live trees at the root, adding additional stressors and increasing the time in which a stress-weakened tree may die.

Clusters of mushrooms of Armillaria mella form in autumn at the base of invaded trees. (Forest Service photo)

“SO – do we just leave the forest alone or intervene? Yes to both.

• Identify dominant stems that serve an important role to your individual property needs (e.g. shades the building to reduce energy consumption during the summer; stabilizes the lake bank).
• Consider performing a thinning of trees on your property to increase stand health and remove excessive leaf litter (which will allow herbaceous vegetation to grow, aid in soil stabilization and increase water quality).

Insects and disease attack weakened trees, so the healthier the tree, the less likely it will succumb to pest, and will perform better during stressful conditions.”

Should property owners replace oaks with other deciduous trees, such as red maple?
“It depends on the remaining tree count. If there are openings in the canopy, then possibly. But what trees remain and will these trees utilize the newly opened canopy? Red maple would not be my suggestion, as maples provide no food source for deer, turkey and other wildlife. Look at native oak, hickory and pecan.”

The colorful leaves of a red oak tree. (Missouri Botanical Garden photo)

Where can property owners buy seedlings?
“The Missouri Department of Conservation sells seedlings – go to their website and do a search. Forest Keeling Nursery sells larger native trees and would be a better choice if you only need to plant a handful of trees.”

While these questions are specific to an immediate problem, does Innsbrook have a general forest management program?
“There are plans for individual owners of homes and chalets to use, providing opportunities to set goals for their property, with restrictions on removal of live trees of certain diameters. This helps ensure no one clears trees just because they want to.”

In closing…
“Each property owner is responsible for their piece of the Innsbrook forest. Each parcel constitutes an approximate 6,500-7,000-acre forest. Caution must be taken so owners do not begin cutting down all the dead trees and applying chemicals. This would be considerably more devastating to our forest health than our current issue of oak decline. Maintaining balance in the ecosystem is more important than drastic measures some may want to employ, believing they are taking appropriate measures.”

Photo by Charlotte Gail