Oak tree decline

Asked September 26, 2019, 1:02 PM EDT

Trying to figure out what we are dealing with now that 4-5 oak trees have this condition in Timonium, MD. Looked like Oak Wilt but that does not seem common around here. Your articles mention a bacteria that causes a similar decline in oaks. Looking for solutions and/or prevention to protect other oaks.

Baltimore County Maryland

1 Response

Oak trees are in decline all over our region, unfortunately — both red and white oaks. There is no single cause. To occur over many oak species and a wide area points to environmental and cultural causes. Higher summer temperatures are a factor.

White oaks are intolerant of saturated soil, so last year’s excessive rain is believed to play a role. Red oaks are especially affected by years of drought. Drowning and drought both kill roots. Root stress can lead to early fall coloration, browning, and/or leaf drop and dieback. Trees stressed by unfavorable environmental conditions become more susceptible to secondary disease issues and pests such as ambrosia beetles and borers.

Some oaks are dying of bacterial leaf scorch, but this is not common on white oaks. Oak wilt is not active in Maryland generally. Here is more about those diseases: https://extension.umd.edu/hgic/why-oak-trees-are-declining

Take a look at this publication about oak decline. https://extension.tennessee.edu/publications/Documents/SP675.pdf

Most declining oaks are 50-70 years old. Bigger trees need more resources than smaller trees and are less resilient. Many trees are surrounded by turf that intercepts rain and nutrients. Whereas a forest tree’s fallen leaves are entirely recycled into nutrients to feed the tree, homeowners rarely leave those leaves on the ground for trees. Lawn mowing itself can compact soil, so rain and oxygen can’t penetrate.

There isn’t really much you can do to reverse decline in mature oak trees. Water your valuable trees and shrubs during this period of drought we're in. See watering tips for drought, https://extension.umd.edu/sites/extension.umd.edu/files/_docs/programs/hgic/HGIC_Pubs/ornamentals/HG...

A certified arborist can evaluate trees for pests and diseases and structural integrity. They also can look to see if there are viable buds on the tree to support new foliage next year. Find a certified arborist near you by using the International Society of Arboriculture website: treesaregood.org.

Since oaks are premier trees, it’s good to replant oaks (and other types of trees). Be sure to protect saplings from deer.