Pruning between April 15 and July 15 should be strictly avoided because this is when beetle activity and viable spores are most prevalent across the landscape. If pruning an oak is absolutely necessary during this time, wounds should be immediately sealed with pruning sealer or water-based paint to prevent infection.
If you are going to trim an oak (no matter how small the cut), make sure you use a tree sealant (ie spray can with black pruning seal in it or you can purchase the same thing that can be painted on) so as to prevent oak wilt.
The systemic fungicide Alamo has been used as a preventative treatment in highly valued red and white oaks, and as a curative treatment in white oaks.
Using a pruning sealant is not recommended. Trees naturally deal with damage and put a natural barrier between the wound and the rest of the tree. Pruning sealers trap moisture and do not let the tree dry out and do the natural healing. Rot and infection can form under sealers and eat away at good tissue.
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.
Live oak trees infected with oak wilt usually die within two to four months.
Avoid Pruning Oaks in the Summer
If you must prune (usually for safety reasons), paint the pruning cuts with latex paint to make them less attractive to fungus-carrying beetles. Here's more information on the best time to trim oak trees and how often.
Alternatively, there are natural tree sealers with ingredients like collagen and aloe gel.
To make a very long story short, synthetic, often petroleum based pruning sealers will stop the tree from being able to grow over the cut area. It isn't a case that they could never be useful, only that most often they are detrimental.
Applying Too Much Sealer
It is important to apply the right amount of sealer. Applying too much can lead to bubbling and cracking which will require more time and money to fix. Make sure that you measure out how much sealant you need before starting and apply it evenly to the surface.
Preventing New Infection Centers
Once an oak tree becomes infected with oak wilt, there is no known chemical treatment that is capable of “curing” the disease; however, fungicide research is continuing.
You can easily treat against infection and death of trees by oak wilt using DIY trunk injection of the fungicide Propiconazole 14.3 using reloadable Chemjet® Tree Injectors. The procedure is as follows for trees that have not yet been infected (indicated by leaves turning brown or falling off prematurely during summer.
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.
Topcoat: Mix two parts polyurethane with one part low-odor mineral spirits, and stir. With experience, you can increase the percentage to three parts polyurethane to one part mineral spirits for thicker coats with each application.
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.
It has the ability to compartmentalize diseases and damage tissue sealing them from the healthy tissues in many instances. These damaged areas then remain in the tree and can be seen many years later if the tree is cut.
Most wounds occur through pruning, but lawn mower scrapes and broken branches should also be sealed as well as the tops of freshly cut stumps. When pruning, spray each wound right after you make the cut so none are missed. There is no need to seal old wounds because they dry out within a few days.
However, if the choice is between this and an asphalt product, vaseline is the better option. Still, we would reserve this as a last resort and only use it on evergreens that produce much sap, like pines and spruces. The vaseline won't affect these trees as badly and is highly effective in stopping sap loss.
Cut your tree limbs at a straight angle on the node to prevent nutrients from allowing the branch to regrow. Mix an FDA-approved growth regulator with water according to manufacturer specifications and apply it to the limb stub with a brush.
By adding pruning sealer you're more likely to seal in moisture, which will slow the healing process and prevent sunlight from drying the wound. Dark areas with trapped moisture are the perfect atmosphere for the development of fungi, which can lead to decay in trees.
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.
Tree Injection With Systemic Fungicide: Trees within the buffer zone can be treated with a systemic fungicide (See Photo). Alamo is the product labeled for use in the control of oak wilt. It is applied by injecting the fungicide into the root flares. Alamo is most effective when applied as a preventive treatment.
Considering the commonality of Oak trees, one of the most common reasons why trees lose their leaves in summer is due to Oak wilt. Oak wilt is a destructive disease that affects oak trees and can cause them to lose all their leaves within a few weeks.