Oak Tree Pruning Practices
 

Oak Tree Diagnostics  Disease and  Prevention

The Oak Tree


Regular oak tree maintenance can keep trees healthy for a lifetime. Oak trees are one of the most common trees in the United States. Indigenous in the northern hemisphere oaks can grow in a variety of habitats. There are over 600 species of oak trees with the most common being the red oak, white oak, black oaks and live oak. Mature oaks can reach heights between 50 and 100 feet. Oak trees are know for their strength, longevity and desirable wood properties.

 

The following infographic provides tips to spotting common pests and diseases, mortality rates, and oak tree maintenance tips. Some diseases, such as Galls are more unattractive then harmful. However, spotting diseases such as oak wilt and root rot early can save the infected tree and prevent the disease from spreading to other nearby trees.
 
 
oak tree maintenance

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Oak Tree Maintenance

 

Oaks are a very “hearty” species of tree. Rarely do oak trees need maintenance, but there are a few common pests and diseases that can harm them if not properly treated. Often the best cure is to maintain a healthy oak tree as many diseases and pests attack trees that are already in weak condition. To keep oaks healthy make sure they get plenty of water during droughts, prune dead or dying branches, and fertilize and mulch annually to provide plenty of nutrients for the tree.

 

       Common Pests

 

  
   Bark beetle 

    Wood boring beetles

  Gypsy moths

   Mites



Common Diseases

 Ceratocystis fagacearum (Oak Wilt)

     Tubakia dryina (Tubakia Leaf Spot)

     Phytophthora (Root Rot)

     Cankers

     

 Wood Boring/Bark Beetles

 Wood boring/bark beetles are small, cylindrical, hard bodied pests often black, dark red or brown in color. In the beginning of an attack it can be difficult to spot a bark or wood boring beetle infestation. Signs of an infestation include small emergence holes in the bark, discolored shoots, sawdust like frass, and sap oozing from the tree. The reason why it can be so difficult to spot an infestation is because signs of bark and wood boring beetles often occur after the beetles have been attacking the tree for a period of time.
 

 

Wood Boring/Bark Beetle Maintenance

 

     Prune and dispose of bark beetle-infested limbs

     Maintain Healthy Trees

     Pheromone traps

     Insecticides

        Remove the tree as a last resort

     

 

Once a tree has a beetle infestation is can be difficult to manage. Insecticides often fail because the beetles are protected beneath the bark of the tree. When removing the tree or pruning infested branches it’s important to destroy them properly. If the wood is not chipped, burned or removed from the property immediately beetles can quickly emerge and attack other trees in the area. Do not pile infested wood next to another tree or shrub.
 
Great resources for identifying and treating Bark/Wood Boring Beetles:


Tree Insect and Diseases
Information Database/ "Trees Are Good" – Insect and Disease Problems

 

Cankers

 

Canker cause a dark or discolored area on the trunk or branches of an oak tree. The infected area may appear flattened or sunken with swollen and cracked edges. Besides for being unsightly, cankers can cause die back of branches and even kill an oak tree if not properly maintained. Symptoms include dying or dead branches, wilted leaves (still attached) among healthy foliage, and discolored bark, sunken and cracked bark.
 

 

Canker Maintenance

  Remove tree

                                                   Paclobutrazol treatment

     

 Managing cankers can be tricky. One method to treat this condition is to use Cambistat a Paclobutrazol based growth inhibitor. Paclobutrazol is a proven chemical to treat and stop the spread of cankers. This growth inhibitor works by halting the above ground growth of the tree. Essentially, you will be robbing the canker of the food and nutrients it needs to develop. This procedure lasts for approximately 3 years. During this time the root systems of the tree will expand rapidly. After 3 years the above ground growth of the tree will return. The growth will be so rapid that hopefully the tree will grow over and seal the canker. As a last resort remove the tree completely if the canker has done significant damage to the trunk. Cankers are caused by a fungus which can be easily spread to other trees in the area by insects or wind.
 
Great resources for identifying and treating cankers:

Sustainable Urban Resources – Fungal Cankers of Trees
 

 

Galls

 

Galls are abnormal growths on oak trees. Galls often occur on leaves twigs, branches or roots. Galls can be caused by a variety of insects. Generally, Galls do not harm a tree, however, they can be very unsightly. Symptoms of galls include irregular plant growths.
 

 

     Gall Maintenance:

          Do nothing; live with the problem.

     Pruning

     Destroying fallen leaves

     Destroying gall-infested twigs and branches

     Watering and fertilizing

     Insecticides

     

 

Despite the unattractive appearance of galls, their presence is usually not harmful to the host plant. Unless the galls appearance are causing unattractive landscaping they often do not need to be treated. To prevent galls from forming on trees its important to regularly prune branches and destroy fallen leaves and branches where insects can spawn and eventually move into the tree. Insecticides can also be used to kill the insects causing the galls.
 
Great resources for identifying and treating galls:
About Forestry – Leaf and Twig Gall Prevention and Control
Missouri Botanical Garden – Galls on Trees
 

 

Gypsy Moths

 

Gypsy moths are not a native species in the United States. They were brought over in the late 1800′s for silk spinning. They have become one of the most destructive insects in the United States causing nearly $1 billion dollars in damage to trees. Gypsy moths attack the vegetation on oak trees and if they become established gypsy moths can defoliate all the trees in the area of outbreak. Symptoms of a gypsy moth infestation include egg masses on tree trunks and branches, caterpillar sightings in late spring, holes in leaves, and defoliation.
 

 

    Gypsy Moth Maintenance

 

     Pesticides

     Pheromone Traps

     Burlap covering to capture caterpillars and pupae

     Removing egg masses

     

 

Before taking action it is important to note how severe the infestation is. When observing the property count how many egg masses there are. If the number reaches ten or more swift action may be required. When treating an outbreak it is most common to remove egg masses and apply pesticides. Sevin SL carbaryl is a great insecticide to combat a gypsy moth infestation. Another common practice is to place a piece of burlap coated with insecticide around the trunk of an oak tree. Caterpillars climbing the tree will get caught in the burlap. Homeowners may choose to use pheromone traps to attract and capture gypsy moths.
 
Great resources for identifying and treating Gypsy Moths:
Iowa State University – Gypsy Moth
West Virginia University – Homeowner’s Guide to Gypsy Moth Management
 

 

Oak Wilt

 

Oak wilt is a very deadly fungal infection that almost always kills oaks. Red oaks are especially susceptibility to the disease and once infected can be killed in just a few short weeks. White oaks can have a stronger resistance to the disease, but it is still deadly. Oak wilt symptoms start at the leaf margins and progress inward. Young leaves wilt turning pale green and brown remaining attached for a period of time. It usually begins on one branch and quickly engulfs the entire tree. Oaks infected with oak wilt decline very rapidly.
 

 

Oak Wilt Maintenance

Fungicide treatment

                                                          Removing tree

     

 

Unfortunately, options are very limited when an oak wilt infection occurs. Red Oaks have nearly a 100% mortality rate and often the best way to fight an outbreak is to remove the infected tree before the disease can spread to nearby trees either through the root systems or from insects. A preventive measure to protect trees from oak wilt is to use fungicides. If an outbreak occurs it can be beneficial to protect other trees using a fungicidal treatment. It is recommended to remove the infected tree before the disease can spread to other nearby trees on the property.
 
Great resources for identifying and treating Oak Wilt:
Texas Oak Wilt – Oak Wilt Identification

 

 Tubakia Leaf Spot

 

Tubakia leaf spot is not a very deadly disease and is often just an unattractive annoyance. Symptoms of Tubakia leaf spot include Small, brown, dot-like fruiting bodies forming on the necrotic tissue of leaves. Recently, Bur oak blight has become an increasing problem. Bur oak blight is a type of Tubakia leaf spot that can cause mortality if left untreated.
 

 

Tubakia Leaf Spot Maintenance:

 Remove infected leaves and dead twigs

                                                 Use fungicides if needed     
                                                    
                                                      Replace the plant

     

 To treat Tubakia leaf spot simply prune infected (dead or dying) leaves and branches from the tree. In rare cases a fungicidal treatment or removal of the oak will be necessary. Usually, young oaks are the only trees that would require this extreme method of treatment when dealing with a leaf spot infection. Often the disease is just an unsightly nuisance to property owners. To treat bur oak blight studies have shown that injecting propiconazole fungicide in late May or early June (before symptoms appear in the summer) have reduced symptoms and can be used to manage high value trees.
 
Great resources for identifying and treating Tubakia Leaf Spot:

United States Department of Agriculture – Actinopelte leaf spot
Missouri Botanical Garden – Leaf Spot Diseases of Shade Trees and Ornamentals
United States Department of Agriculture – Bur Oak Blight

 

 Root Rot

 

Root rot is one of the most deadly diseases that can infect oak trees. Root Rot can be caused by a bacterial or fungal infection such as Rhizoctonia, Fusarium, Amillaria, or Ganoderma. Unfortunately, due to the close similarity between symptoms of bacterial and fungal root rot it’s tough to distinguish with the naked eye. One method of determining whether or not there is a fungal or bacterial infection is to take a sample of the roots and smell them. If the roots smell sour this indicates it is a bacterial infection. Symptoms of root rot include older leaves yellow and fall, margins of leaves die, roots become limp, honey colored mushroom around base of tree in the fall, die back of branches and limbs, and white fungal mat over roots. Butt rot which effects the root flare of a tree can also turn into a canker if left untreated (see canker maintenance for more information on how to treat this disease).
 

 

Root Rot Maintenance

  Air spading

     Remove trees to prevent spreading

     Growth Regulators (see canker maintenance)

     

 Similar to oak wilt there is not much of an opportunity to treat root rot on an infected tree. When a bacterial infection occurs use a technique called air spading and remove the soil around the root flare of the tree. By removing the soil you will allow excess moisture to dry out and this might help slow or kill of the bacterial infection. There is little that can be done to stop the spread of fungal root rot. Usually, the best coarse of action is to remove the infected tree before the disease can spread to other nearby trees on the property.

 

Note: On mature oak trees (especially White Oaks) its important not to disturb the roots of a mature tree. Oak trees do not respond well to construction or landscaping/excavating that can destroy or damage the roots of the tree that has already become established.
 
Great resources for identifying and treating Root Rot:
The Morton Arboretum – Armillaria Root Rot and Native Oaks
Penn State College of Agricultural Sciences – Fungal Root Rots And Chemical Fungicide Use

 

 

 

Maintain Oak Trees To Keep Them Healthy

 

Oaks are generally very strong and resilient to fungal infections and pest infestations. The best method of treatment for all the diseases covered in this document is to use preventative measures. In most instances, trees that become ill are already in a weakened condition. Annual mulching and fertilizing can ensure the trees have the proper nutrients they need. During times of drought make sure oaks receive enough water to keep them strong.

 

Young Oak Trees

 

Pruning dead or dying branches can also help stop or slow the rate of infection of many diseases. On young oak trees structural pruning prevents the need for large pruning cuts in the future. It is recommended to prune trees during dormant winter months. For young oaks use a higher concentration nitrogen fertilizer to promote healthy plant growth. Young trees also need more watering, especially after planting (volume depends on species).

 

Mature Oak Trees

 

Young oaks and old oaks need different care then old oaks. Old oak trees need fine pruning if they were structurally pruned when young. Mature oaks trees do not go through large growth so fertilizers should be low nitrogen fertilizer.

 

Taking time to do proper oak tree maintenance a few times during a season will help keep trees healthy and free of disease and pests. Since oaks are so durable we tend to forget they do need some care to help keep them healthy. Monitoring trees over the course of the season helps make sure they are not suffering from and disease or pest infestations. Also, if a disease or pest infestation breaks out the earlier you can catch it the better chance you can stop it from destroying the tree or spread to other trees on the property.


Oak Tree Pruning Practices

Live Oak Tree Pruning



You live in one of the most scenic neighborhoods in the Texas Hill Country, known for our beautiful homes,and our majestic Oaks. Our live oak trees are our neighborhoods crowning glory. So, preserving and caring for them is extremely important to your landscape values and their beauty. One might say, our live oaks eke a survival out of Texas because of the extreme harsh climate and soil conditions in which they must live, and yes they thrive in spite of our latest extended drought conditions.

Our Live Oaks around homes and cities require certain conditions to survive and prosper. The homeowner should be concerned regarding the landscape activities of planting near oaks, irrigation and feeding, pruning, disease and insect infestations. Most native oaks in Texas evolved and prospered in an environment typified by a cool, moist winters and hot, dry summers. Under natural conditions, surface soils are wet during the cooler months and become dry by summer. Natural vegetation growing around and beneath oaks are usually dormant during the winter and flourishes during spring and by late summer, and into early fall creating the well-known golden-brown landscape, of Texas' valleys and foothills. Native live oaks, however, remain green because their thick, leathery leaves and other adaptive features reduce their growth rate and water use. The homeowners should attempt to approximate the natural environment in which these magnificent trees are in their natural setting. When cared for properly, live oak has a moderately rapid to slow rate of growth.

SOUTHERN LIVE OAK (Quercus virginiana) - A large, sprawling, picturesque tree and it is highly desirable as a landscape tree. The Live Oak is one of the broadest spreading of the Oaks, providing large areas of deep, inviting shade. Reaching 40 to 60 feet in height with a 60 to 100 foot spread and usually possessing many sinuously curved trunks and branches. Live Oak is an impressive sight for any large-scaled landscape. Give it plenty of room since the trunk can grow to more than six feet in diameter. An amazingly durable American native, it can measure its life in centuries if properly located and cared for in the landscape. In Texas, live oaks learned ten thousand years ago that Texas soils and environmental conditions are not conducive for propagation from the acorns. They depend on animals and birds to transplant acorns away from the parent tree for the sake of forest diversity. Live oaks are very bad parents and do not want competition from their siblings, so they predispose a fungus to kill the germination of the acorns that remain under the tree. Live oaks propagate in a very unusual manner, they put out ramets (sending-up root sprouts) from the mature roots, or otherwise a bud that grows off the root. This method ensures 100% survival as the new shoots have a fully mature root system for support. They actually clone themselves, a Mott or grove of a few or up to hundreds of trees are really all the same tree and can cover large acreage areas.

Planting Near Oaks

Only drought-tolerant plants that require no summer water should be planted around old established oaks and they should be planted 6' from the base of the tree. DO NOT plant exotic grasses, ivy, or other vegetation requiring summer irrigation near them.

Irrigating and Fertilizing

Native live oaks usually do not require measurable amounts of irrigation, however they usually thrive in our suburban landscapes if properly cared for. Healthy live oaks are even able to survive the excessively dry summers. Frequent, shallow watering not only encourages crown and root rot, it results in ineffective shallow roots near the surface. Under no circumstances should the ground near the base of a live oak be allowed to become moist during warm periods. Deep watering at the critical root zone, which the drip edge and outward is far more effective and responsible.

Mature trees usually need little supplemental nutrient replacement. Fertilization should be done only to maintain vigor and if growth is poor. Lighter and frequent applications will produce better results and allow the trees to grow at a more natural and slow rate. Heavy fertilization will create rapid, lush growth, which is a loud dinner bell for insects and other disease. Excessive fertilization causes the tree to divert its defense energy against disease and insects, to growth. Trees that have recently undergone severe pruning or root damage should not be fertilized for at least six months.

Pruning

Pruning should be done only during the hottest time of year, late June to October and the coldest time, late November to mid February for the evergreen species of oaks. . Keep in mind that the canopy and root system must always be kept in balance, moderation is the best policy as excessive pruning may well jeopardize the tree’s overall vigor and health. Some research has shown that, wound dressings or sealing compounds tree paint do more harm than good. Yet all tree companys use a wound sealer and I seal all cuts to be on the safe side.

Because of the risk of oak wilt,an inexpensive Black spray paint is best applied to seal the wound and at the same time allow the wood tissue to cure properly. Pruning should be performed by an experienced arborist or homeowner familiar with oak pruning according to the pruning standard of the Texas Chapter of the International Society of Arboriculture.


"Pruning Notes"

Recognizing Live Oak Pruning maintainance needs and susceptable tree health issues.

All Dead Live Oaks should be removed immediately upon decline.

Most Oaks develop mechanical growth problems which can be caused by self inflicted wounding {rubbing/Branch crossing,abrasions) usually due to neglect which can become a haven for insects,usually ants or a potential disease infection or branch transmission point.

This includes interlocking limbs that rub against each other, prune, remove,repair and seal these issues ASAP.

Dead wood must be removed usually with a small top handle arborist chainsaw( Echo,Stihl,or Shindaiwa) by making a smooth flush cut above the dead branch paralell to the main branch.

A relief cut above dead branch intersection can reduce weight and pressure and prevent the cut and bark from tearing on medium to large limbs Then immediatly seal the cut with tree-cote or a thick coat of cheap black spray paint.


Remember safety is most important and use ropes and relief cuts to prevent binding, Also to secure large branches and be sure of your exit and use a tree safety harness as needed for high work and good common sense will ensure a successful and safe job.

Branches rubbing on roofs,other branches or other structures must be cut back as the abrasion is a potential insect disease transmission point.

This will significantly reduce the possibility of Oak Wilt wound infection by reducing insect vector transmission points.

Trees growing up into and possibly rubbing other branches through the dome or crown of other susceptible Live Oaks. This type of abrasive wounding, will never heal, and will flow sap year around. The flow will be heaviest during peak insect and fungal mat formation periods. All pruning cuts made by man, even large or incompetent cuts, will stop flowing sap within a couple of hours. If these wounds are properly treated with pruning paint, there will be no sap flow at all and the wound will be unattractive to the insect. Therefore, properly pruned Oaks are less likely to become infected by sap feeding insects.

1. Trees that need to be pruned, should be pruned, by a educated tree savy homeowner familiar with safe oak tree pruning practices or experienced pruner or professional Arborist, as soon as possible. Removing all smaller lower and dead branches will help push the growth to the upper branches ands provide better growth structure to the upper canopy and enhance overall tree health.

Overall Live Oak tree health will improve the overhead canopy as the trees "Dome Out" and growth will improve branch health structure by allowing denser growth.

2. Try to avoid leaving knobs sticking out as they are unsightly and susceptable to decay and insects love these places. Flush Cut and seal all knobs and wounds ASAP.

3. When pruning trees of deadwood, cuts susceptible to decay and or harboring insects(usually ants)always remove the safe harbor by eliminating the facilitation and transmission vehicle points of disease infection to the trees.

4. Always use a non-phytotoxic wound sealer such as tree-cote or paint should always be used on every cut ASAP.



Diseases and Insects

Native Texas live oaks are relatively tolerant of most diseases. In early spring, timed at leaf out, live oaks can be attacked by a barrage of leaf eating insects. The cankerworm and leaf rollers are the most common predators and can literally defoliate a tree over night. However, using a safe foliar application of Bt (a Bio-pesticide) can keep them under control. It is most unfortunate, they are subject to OAK WILT which has devastated many trees in parts of central Texas. Studies have shown that they can be replanted successfully in old and developing oak wilt centers. Precautions must be taken to prevent wounding. Wounds attract sap feeding beetles that carry the oak wilt fungus spores. If the tree is wounded or it has to be pruned, immediately paint with a light application of spray paint. The light dressing application of paint forms an insect barrier and allows the wound wood to properly cure.

Diseases and other problems when over watered or improperly pruned attack trees weakened by disturbance or improper care. Disease infected trees decline slowly over a period of years if not attended to. However, if oak wilt and other diseases are caught in the early stages, a tree can be saved. Early diagnosis and comprehensive treatment is best left to a qualified arborist.

Major foliage diseases of live oaks are: oak leaf blister, twig borers, diplodia (twig fungus), anthracnose and powdery mildew. Seldom do these diseases become severe enough to require treatment.

Soil Compaction and Trenching

The root zone or rhizophere under a tree is like a fresh piece of baked bread, it contains all the caterpillars, gases (oxygen, hydrogen and nitrogen) moisture, microbial life and nutrients. When compacted or squeezed flat like a tortilla, all the gases, moisture and nutrients are no longer available. This soil compaction under a tree can cause serious root damage and crown loss over extended time. Contractors should take all necessary precautions to protect trees during construction and many trees are two and three hundred years old and can never be replaced. In all my years, I have never been able to place a significant value on a near 400 year old live oak tree. This is priceless! An eight year old boy summed it all up... " That is a non-renewable resourse of energy" !!!!! That changed my attitude!

Trenching near the critical root zone is often overlooked as a cause of tree death. Trenching usually occurs when underground utilities are installed. Digging a trench within the root zone can severe a significant portion of a tree's roots and cause damage to the tree. Ninety five percent of all tree roots are within the top 12 to 16 inches of the surface soils and can extend three times beyond the drip edge.

Landscape Paving, and Landscape Fill Around Oak Trees

Paving can cause the same problems associated with soil compaction. Paving prevents water from soaking the soil and impedes the exchange of gases between roots, soil and the atmosphere. Excessive moisture trapped by fill material can also cause root and crown rot. It is best to avoid tampering with the natural grade, or to leave the natural grade within the root zone alone and use retaining walls. Poor drainage is a common cause of oak tree deaths as adequate drainage is critical to ensure a proper balance of moisture, air and nutrients to grown and survive.

Live Oak (Quercus virginiana and Q. fusiformis) are widely adapted species. In addition there are numerous hybrids between the two species. They provide shade during the winter as well as summer months. Leaf shed is during the early spring and trees will be completely defoliated for only a few weeks, at which time replacing new leaves and blossoms simultaneously This is why it is known as an evergreen oak.

The live oak tree tolerates a variety extremes, from of high acid soils and climate conditions extending from Virginia down along the east coast to Florida. They tolerate salt conditions and extend across the coastal plains and into the rocky hill country in South Central Texas with high alkaline soils, and hot dry summer heat. They extend west to California for the cools moist winters and hot dry summers. That is our majestic Live Oak Tree

Live Oaks, can get Oak Wilt by way of root transmission from another Live Oak, or from the sap feeding, Nitidulide beetle. This insect would first have to have fed from a tree with an infected fungal mat. A fungal spore can stick to its body, then be carried to the next tree that the insect feeds upon. Red Oaks are the most common tree to produce this infected fungal mat.

Insect transmission does not occur from Live Oak to Live Oak as Live Oaks are incapable of producing the infected fungal mat and fungal spore.

When Oak Wilt travels through the grafted root system of Live Oaks, it is at a rate of about 75 feet per year. Spread at a rate of 150 feet per year has been documented.

Spanish/Red Oaks primarily get Oak Wilt by insect transfer. Spanish/Red Oaks do not develop grafted root systems. Furthermore, Spanish/Red Oaks are one of the few trees known to produce the infected fungal mat and fungal spore, that can be transported by way of sap feeding beetles. This infected fungal mat most commonly forms in mild temperatures, for the first year following the trees death from Oak Wilt. Spanish/Red Oaks can not be salvaged once they have contracted the disease.

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