Oak Mortality Issue Paper

Mark Twain National Forest

July 2, 2001

The Problem:

Prolonged drought in southern Missouri has weakened oak trees in the Ozark Highlands 

region of the Eastern central hardwoods ecotype. 

• Some parts of southern Missouri are 25 inches below normal rainfall over a 2 1⁄2 

year period. 

• Once the trees are weakened by drought, two oak-boring beetles accelerate the 

death of the trees. These beetles are the red oak borer and the two-lined chestnut 

borer. 

• Early spring defoliation by loopers and other pests in some places has further 

weakened the drought stressed trees. 

• A fungus attacks the root systems of stressed trees. 

• These factors are combining to cause widespread mortality in red oaks, especially 

mature and over-mature scarlet and black oaks. 

• The problem is widespread across the Mark Twain and southern Missouri, even 

immature red oaks and white oaks are being affected.

• Plots taken from November, 2000 to February 2001 on the Salem/Potosi Ranger 

districts indicated that 70 to 90% of the scarlet and black oaks are affected by 

drought and insects, and about 20% of those affected are dead. These numbers 

will probably be higher as the summer progresses.

• Red Oak borer populations and damage are expected to skyrocket in summer 

2001. Eggs laid in weak trees with diminished sap flows are expected to have 

higher than normal survival rates. The red oak borer breeding population is 

already at historical high levels.

• No direct treatments are available for the immediate remediation of this mortality. 

Timber management activities must be used to mitigate effects over long periods 

of time.

What can be done about the problem: Short-term

• Salvage cutting of dead/declining red oak, other oaks, and removal of red oak 

borer brood trees.

• Temporary control of mid-story shade –tolerant species to encourage oak and pine 

regeneration

• Regenerate by uneven-aged and even-aged harvest methods to encourage white or 

post oak and pine regeneration.

• Prescribed burning to encourage development of white or post oak and pine 

regeneration, and reduce competition from shade tolerant species.

Long term:

• In areas of less severe mortality/decline and in areas that may be vulnerable to 

decline, hazard rating systems may be useful in identifying stands vulnerable to 

decline.

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• Silvicultural treatments such as mid-story control, thinning and prescribed 

burning can be used to keep oak stands healthy and encourage healthier oak-pine 

mixes.

• Regenerate vulnerable stands before the oaks completely lose their ability to 

sprout.

 

What is being done:

• The Northeastern Area Forest Health Protection unit, St.Paul, MN, conducted a 

biological evaluation. Oak mortality was mapped from the air in September, 

2000, and a report completed March 27, 2001. The information from this effort 

was used to determine the focus of an Environmental Impact Statement that is 

currently under way. 

• The Environmental Impact Statement is being conducted on 25,000 acres of the 

Mark Twain National Forest for commercial harvesting of dead and dying timber 

and to improve forest health in parts of Crawford, Dent, Reynolds and Iron, 

Washington, and Shannon counties.

• Communication and coordination with the Missouri Department of Conservation, 

the Ozark National Forest, Missouri Forest Products Association and Forest 

Service’s Research and State and Private branch is ongoing.

• A Mark Twain National Forest Strategy for dealing with the oak mortality is 

being developed in July. 

Economic Effects to the timber industry in Missouri:

• Oak trees make up 40-50% of the trees on the 1.5 million acres of the Mark 

Twain NF located in 29 counties in southern Missouri.

• Currently 33% of lumber being sawn at some mills is reduced by one grade due to 

red oak borers. Trees that have been dead more than two years have limited 

commercial value. The products from two-year-old dead trees would be chips or 

firewood.

Further concerns:

• Oak mortality in northwest Arkansas is widespread and the damage exceeds 

estimates made two years ago.

• Missouri is about two years behind Arkansas’s outbreak of oak borers. Salvage 

operations and brood tree removal needs to occur before the peak of infestation.

• Public health and safety is top priority. Roads, recreation sites, and other areas of 

human concentration need to be inspected, and weakened trees should be cut 

down. A tree fell on a moving car in Arkansas recently. 

• Wildfire hazard is greatly increased due to the fuel build up and an increase in 

fire intensity in areas of mortality. 

 

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