To slow above-ground movement of oak wilt, cut down diseased oaks in late autumn or winter after all trees have dropped their leaves for the fall.
Homeowners can reduce the risk of oak wilt infections by not pruning or otherwise injuring oaks after April 15. While high risk of infection decreases to lower risk after mid-July, it's prudent to simply avoid pruning oak trees from just prior to bud break to leaf drop. This means April to November.
For this step to be successful, several “healthy” oaks surrounding the pocket of wilting or dead oaks usually need to be sacrificed because they likely already have oak wilt in their root systems. The treatment boundary installation usually occurs from August through early winter, depending on the method used.
Oak wilt is most active from April to July, which is why you should never trim oak trees in the summer. To be safe, you should avoid pruning between April 1 and November 15. Davey arborists recommend pruning oak trees between November 15 and March 31.
Firewood from unknown origins should be burned during the winter months. If possible, do not store it to the next season. (Note: Burning firewood with oak wilt spores does not spread the fungus! Fungal spores burn, too.
Trees in the red oak group generally die rapidly, usually within weeks or months after infection. Treatment will not save an infected red oak. Trees in the White oak subgenus, such as Burr oak and Chinkapin oak, can generally be treated for oak wilt and will recover within a year of treatment.
Use the sound test
Your firewood is dry when the sound is hard and ringing. Moist firewood has a dull sound. Be aware of pitfalls when it comes to the sound test. In frosty weather and when the temperature is below 0° Celsius, fresh wood can give off a high and ringing sound even if the wood is not yet dry.
Pruning mature oak trees at home is best kept to the smaller, lower branches that need pruning. Any branches up high in the tree should be left to a professional to cut.
A good indicator of oak wilt infection is a carpet of leaves under an oak in mid-summer. Red oaks infected with oak wilt lose about 90 percent or more of their leaves in 1–2 months; bur and white oaks quickly lose leaves from a few branches during the summer over several years.
As the beetles feed on the sap of the pruning cut, fungal spores get into the fresh wound, infecting the tree. Pruning oak trees in winter greatly reduces the risk of an oak wilt infection as the beetles and fungal mats are not present at that time of year.
Chemical Control Using Fungicides
Fungicides have been developed that may be effective in preventing oak wilt when injected into living oak trees without active symptoms. A single treatment can protect red oaks from developing symptoms for 2 years following injection.
If there is concern that a red oak may have been infected with oak wilt, then its wood should be immediately burned, buried, or chipped. Fire will kill oak wilt, and there is no risk of spores being transported by smoke.
Spread through Roots
Infection centers among live oaks in Texas expand at an average rate of 75 ft per year, varying from no spread to 150 ft in any one direction.
Yes, it is perfectly safe to prune dead oak branches any time of the year; however, please avoid cutting into live tissue around the bark collar and around the branch bark ridge.
Live oaks go through a process called molting every year when the weather starts warming up after winter. Molting is the process when live oaks drop at least 50% of last year's leaves and then grow back fresh leaves within the next month or so. Typically, this would start around March or April.
WATERING NATIVE OAKs PROPERLY
Under natural California conditions, the Armillaria is dormant during the hot, dry summer, and comes to life only with the rains. Should I water my native oak in the summer? Yes, but not more than once a month and not around the trunk.
Cutting down a tree with oak wilt that is still partially alive can cause the disease to spread, but removing it during the least vulnerable months can prevent this.
The disease is a particularly serious problem for species in the red oak group such as northern red, northern pin and black oaks. Once wilting symptoms are apparent on a red oak, the infected tree will lose most of its leaves and die within approximately one month.
These trees often are cut into firewood and moved, sometimes many miles from their original locations. Any wounding of oaks in this new location can result in new oak wilt infections as beetles move spores from the diseased firewood to fresh wounds on otherwise healthy trees.
Contrary to what many homeowners assume, summer is the worst time of year to cut off oak branches. Instead, it's best to prune from late fall to early spring—November 1 to March 31, to be precise. These are the months when oak trees are less vulnerable to disease and infestations.
The branch bark ridge is the dark, rough bark ridge that separates the branch from the main branch or trunk. Pruning just beyond the branch collar and branch bark ridge retains the tree's natural defense mechanisms and promotes compartmentalization and callus formation. Do not make flush cuts when pruning trees.
Oaks in general do not require much maintenance and when pruning is needed it is best to do it in the winter months or early spring, between November and March.
To identify trees infected with oak wilt, watch for wilting leaves in the upper canopy. Wilting leaves may develop yellow margins, while the interior portion of the leaf remains green. As the tree continues to wilt, leaves turn brown and fall from the tree.
Hardwoods produce more heat when they are burned but take about 18 months to properly season, whereas softwoods can be seasoned in 6-12 months and have the added bonus of being easier to cut and split, making them more appealing for many who cut and prepare their own wood.