Oak wilt

[coolbrze]

What are the symptoms of Oak Wilt? I've done some research on it, but am looking for the experts opinions. What's the best way to deal w/ and cure it?

 

[Bodark]

Check the leaf, resembles bacteria leaf scorch. Take some leaf samples to extension agent for testing. I did a macro trunk injection using Alamo on 2 red oaks probably 5 years ago. Seemed to cure the problem, trees are still doing well today.

 

[coolbrze]

Does this look like Oak Wilt to you? If so, how do you recommend treating this guy? Thanks!

 

[Urban Forester]

It COULD be. Browning starts at the margin, then progresses to the petiole, then the tree defoliates. Red Oaks have no resistance, and it will move VERY quickly. New infections are created by a picnic beetle that feeds on infected tissue then moves to a healthy tree. It is then moved within the infection center by root grafts. There is no chemical control for infected Red Oaks. Macro-infusion of Alamo fungicide in HEALTHY Red Oaks will help, BUT if they are root grafted to an infected tree, then they WILL most likely get it too. Sanitation is key, once ID'd sever ALL root grafts from the infected tree. Macro-infuse those trees that were root grafted. hope this helps.

 

[Jane_Whitt]

Symptoms in Red Oak
The main period of infection is in the spring when the new timber ship is being formed. Symptoms in the red oak occur as early as May. The leaves turn dull green or bronze, are filled with water, shrivel, and then turn yellow or brown. Damage occurs from the tip and the outer edges towards the midrib and base. Wilting leaves are rolled into the central nerve and the line between the bronze and green tissue of individual leaves is very different, these symptoms appear quickly over the crown, often within a couple of weeks, and leaves at the ends of the branches fall
The disease progresses rapidly, and some trees die within 1 or 2 months after onset of symptoms. Most trees die within a year. Growth spurts often branch from the trunk and larger during the year or the year following defoliation.
Symptoms in White Oak
Symptoms of the disease are much more variable in the white oaks, although symptoms are often the foliage of the same. In a few, especially oaks strawberries, the symptoms are essentially the same as red oaks, and the tree can die in one growing season. In general, however, white oaks die slowly. Only one or two branches may show symptoms and die within a year. If the fungus persists, some branches die in a season, and for several years, the tree may eventually die Cline. Some white oaks seem to recover from the disease but can carry the pathogen and serve as reservoirs asymptomatic.
White oak, unlike the red, often have discolored the patient infected annual rings. Mats fungus rarely appear in the white oaks.
Natural root grafts and insect vectors spread the oak wilt fungus from diseased to healthy trees. Healthy oaks growing next to the infected are infected through their roots. Root grafts (Fig. 5) offers a way to transmit the fungus and are an important factor in the spread, especially in areas with deep, gritty, dense, pure red oak.
The fungus overwinters as mycelium in still living, infested trees and mushrooms as platforms of dead trees. The fungus can spread over a mile at least two groups of insects: the sap and bark beetle feeding.
Control :
Unfortunately, there is no known way to save a tree infected with oak wilt fungus. The only way to keep trees healthy is through prevention. Early detection and prompt removal of root grafts dead or dying trees, and the split between sick and healthy trees are essential.
Mechanical and chemical barriers between patients and healthy trees can stop the spread of oak wilt fungus through root grafts. A plow trencher or vibration can be used for cutting or breaking the roots of the trees to a depth of 2 to 4 feet (0.6 to 1.2 m). Soil fumigants can also be used to kill the connection between the roots of trees.
Detailed procedures for the construction of mechanical and chemical barriers are given in the brochure refers to French oak wilt and Stienstra. Punctuality is important. The earlier root grafts between diseased and healthy trees are destroyed, the better the chances of saving the trees nearby.
To suppress the spread of the fungus on the ground, the control should be the goal of destroying the source of inoculum - the diseased tree - at the right time. All trees that die in a given year should be observed carefully for fungi and colonization of oak bark mats beetle April 1 next year. If the carpet or beetles are present, the whole tree should be burned, chipped, or covered with plastic for 60 days. In the eastern United States, about 50 percent of diseased trees contain beetles and about 25 percent produce carpets, however, these figures may vary depending on geographic location. Fresh pruning wounds may attract insects contaminated with the oak wilt fungus. Because of this, avoid unnecessary pruning and pruning in the winter, whenever possible. Trees should not be pruned during April, May or June or whenever the beetles are active

 

[Urban Forester]

Symptoms in Red Oak
The main period of infection is in the spring when the new timber ship is being formed. Symptoms in the red oak occur as early as May. The leaves turn dull green or bronze, are filled with water, shrivel, and then turn yellow or brown. Damage occurs from the tip and the outer edges towards the midrib and base. Wilting leaves are rolled into the central nerve and the line between the bronze and green tissue of individual leaves is very different, these symptoms appear quickly over the crown, often within a couple of weeks, and leaves at the ends of the branches fall
The disease progresses rapidly, and some trees die within 1 or 2 months after onset of symptoms. Most trees die within a year. Growth spurts often branch from the trunk and larger during the year or the year following defoliation.
Symptoms in White Oak
Symptoms of the disease are much more variable in the white oaks, although symptoms are often the foliage of the same. In a few, especially oaks strawberries, the symptoms are essentially the same as red oaks, and the tree can die in one growing season. In general, however, white oaks die slowly. Only one or two branches may show symptoms and die within a year. If the fungus persists, some branches die in a season, and for several years, the tree may eventually die Cline. Some white oaks seem to recover from the disease but can carry the pathogen and serve as reservoirs asymptomatic.
White oak, unlike the red, often have discolored the patient infected annual rings. Mats fungus rarely appear in the white oaks.
Natural root grafts and insect vectors spread the oak wilt fungus from diseased to healthy trees. Healthy oaks growing next to the infected are infected through their roots. Root grafts (Fig. 5) offers a way to transmit the fungus and are an important factor in the spread, especially in areas with deep, gritty, dense, pure red oak.
The fungus overwinters as mycelium in still living, infested trees and mushrooms as platforms of dead trees. The fungus can spread over a mile at least two groups of insects: the sap and bark beetle feeding.
Control :
Unfortunately, there is no known way to save a tree infected with oak wilt fungus. The only way to keep trees healthy is through prevention. Early detection and prompt removal of root grafts dead or dying trees, and the split between sick and healthy trees are essential.
Mechanical and chemical barriers between patients and healthy trees can stop the spread of oak wilt fungus through root grafts. A plow trencher or vibration can be used for cutting or breaking the roots of the trees to a depth of 2 to 4 feet (0.6 to 1.2 m). Soil fumigants can also be used to kill the connection between the roots of trees.
Detailed procedures for the construction of mechanical and chemical barriers are given in the brochure refers to French oak wilt and Stienstra. Punctuality is important. The earlier root grafts between diseased and healthy trees are destroyed, the better the chances of saving the trees nearby.
To suppress the spread of the fungus on the ground, the control should be the goal of destroying the source of inoculum - the diseased tree - at the right time. All trees that die in a given year should be observed carefully for fungi and colonization of oak bark mats beetle April 1 next year. If the carpet or beetles are present, the whole tree should be burned, chipped, or covered with plastic for 60 days. In the eastern United States, about 50 percent of diseased trees contain beetles and about 25 percent produce carpets, however, these figures may vary depending on geographic location. Fresh pruning wounds may attract insects contaminated with the oak wilt fungus. Because of this, avoid unnecessary pruning and pruning in the winter, whenever possible. Trees should not be pruned during April, May or June or whenever the beetles are active

What/who is the source of this info, just curious...

 

[Ed Roland]

Trees should not be pruned during April, May or June or whenever the beetles are active

Welcome to the site Jane. Thats quite a bit of informantion.

Some arborists (Reed-Oakwilt) in effected areas are experimenting with Neem as a supplement in the chainsaw oiler to suppress fungal and vector activity on fresh pruning wounds during the "warm months". I would not assume its ok to prune susceptible oaks up to March 31 or on and after July 1st. Pretty much, if the bug zapper in the backyard is zapping then possible vectors are out and about. Heat units instead of calendar dates. Obviously, I'm not convinced that other insect varieties are not also potential transmission sources.

Mixed with bar oil @ 1 oz. per gallon is apparently an effective deterrent from docking organisms and insect vectors. You should only need several hours of protection before the tree has set in place its own protection. I would expect the Neem to have a residual presence beyond the trees ability to perform initial codit. This might make more sense than painting with a sealant, imo. So while pruning oaks in in my state is not such a problem, pruning susceptible oaks in Texas might benefit from this "chainsaw supplement" during the entire growing season.

ed