Twolined chestnut borer management


oak tree with orange leaves crown

Oak stands stressed by drought and defoliation are vulnerable to attack by twolined chestnut borer and Armillaria root disease. The following tips will help minimize excessive twolined chestnut borer damage:

  • Postpone harvesting or road-building for at least three years after defoliation and four years after drought.
  • Salvage-harvest in infested stands only on frozen ground.
  • Wait to salvage firewood for at least one year after oaks have completely died.
  • Thin overly crowded oak forests when they are not stressed.
  • Diversify oak forests.

Thinning during or shortly after a stress event can greatly increase mortality from twolined chestnut borer. It is important to stay out of stressed stands to allow them to recover. Attempting to "eradicate" twolined chestnut borer from a stand by removing infested trees is not possible; twolined chestnut borer outbreaks usually are the result of widespread drought, so it is not possible to manage populations. They naturally decline on their own.

Salvaging attacked and dead oaks is an option to utilize high-value timber before it degrades. Mark dead and dying oaks during late summer. Harvest marked oaks only on frozen ground, and do not harvest in areas of the stand unaffected by twolined chestnut borer.

If you want to make firewood from dead oaks, delay salvaging for at least a year after the oaks have died. Firewood quality will not deteriorate during this period, and waiting a year will prevent you from moving twolined chestnut borer into uninfested areas. Harvest only on frozen ground.

Some losses from twolined chestnut borer could be avoided by carefully tending forests before inevitable stresses. Thinning overly crowded forests and diversifying tree species within forests could decrease the impact of twolined chestnut borer.

Yard trees

Prevent twolined chestnut borer attack by keeping your oaks as free from stress as possible. Avoid adding soil over roots, do not fertilize stressed oaks, and do not allow herbicides to contact oak leaves. Mulch trees properly. If rainfall is inadequate, watering oaks weekly may be the best method to prevent twolined chestnut borer attack. Water with a soaker hose under the drip-line for several hours.

If an oak tree in your yard is infested (e.g., the top half of its crown died in one growing season), cut it down and dispose of it during the winter (but make sure you are not misdiagnosing oak wilt). Removing infested oaks may save your other oaks from being attacked.

Finally, avoid bringing fresh oak firewood into your yard. Make sure the firewood has been seasoned for at least one year before bringing it to your property, or use MDA-certified firewood.

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