Posts Tagged ‘oak wilt’

Oak Wilt Management/Prevention

Treatment for a tree infected with Oak Wilt involves a fungicide-injection system installed by a state-certified technician.

The balance of nature relies on a diversity of native tree/plant species as a natural defense against insects, pathogens and many other threats. By planting native tree species tolerant of Oak Wilt and diversifying the species we plant, we not only suppress various pathogens and insects, but we encourage a diversity of wildlife and habitat.

Although it is always wise to keep your trees healthy to defend against a great many problems, when it comes to Oak Wilt, a healthy tree can be infected just as easily as one that is not. As an analogy, our children are genetically predisposed to chicken pox and even healthy children can get it. The same is true with live oaks and trees in the Red Oak group; they can be infected with Oak Wilt, even when they are healthy.oak

Oak Wilt Management/Treatment

If trees are confirmed to be infected a few homes away from you in any direction, identify your higher quality trees that may be a susceptible species and which may be in close proximity to the infected trees (within two or three standard city lots). Higher quality trees are selected for treatment because the process can be expensive (costs vary around the state).

It is important to note that research has not provided an organic solution for Oak Wilt to date. Our only research-based option is to directly inject the vascular system of healthy trees to be protected with a fungicide (Propiconazole). While we prefer not to drill small holes into trees, it beats watching your favorite tree succumb to the disease.

The fungicide injection does not “cure” an infected tree, but acts to suppress the symptoms by preventing their visual appearance. In addition, it does not prevent the pathogen from spreading to nearby trees.

The fungicide is very effective in suppressing the symptoms when it is injected before an infection occurs. If a tree is already infected, success in saving it depends on many factors. However, a tree can sometimes be saved if it is treated shortly after infection. Preventative fungicide injections can protect trees for up to two years. Infected trees may require more frequent injections. The duration of repeated injections depends on the amount of disease pressure from nearby infected trees that were not previously treated.

Fungicide injections should be completed by an applicator certified by the Texas Department of Agriculture – a person with specific training in Oak Wilt treatment. The root flare of the tree should be completely exposed because injections in this area allow a more even distribution of the material through the vascular system. Holes are drilled every 4 to 6 inches, and a closed system of tubing and injection tees is hooked to a pressurized tank to deliver the fungicide.

After the system is installed, the majority of the fungicide uptake occurs in the first four to eight hours. Very little distribution takes place after 24 hours.

As a side note, if you have the opportunity to purchase the “perfect house” surrounded by oaks, consult with someone who has specific training and experience in successful Oak Wilt management (often referred to as a pre-purchase tree inspection) before your purchase, or you risk potential disappointment in the future.

I hope some of your fears are now diminished. It is certainly a dry subject to cover. Sometimes I walk in the woods, or climb a tree to reduce the level of stress and search for some sense of sanity in the world. As a friend once noted … too bad I never find any!

About the author: Steve Houser is a Dallas native with more than 30 years of experience as a consulting arborist and tree climber. He is the president of Arborilogical Services Inc., “The Experts Your Trees Deserve.” www.arborilogical.com.

The primary method of preventing Oak Wilt is to avoid planting live oaks and susceptible species in the Red Oak group. Consider planting oaks in the White Oak group, and diversify the other species of trees you may plant. Although a long row of oaks may be aesthetically pleasing, planting of too many of any one species together can create problems. If you line your streets with elms, over time Dutch Elm Disease (Ceratocystis ulmi)can wipe them out. If you plant too many pecans together, the webworms will love you as they eat every leaf — but the trees will curse you!

Last month’s article covered basic information about Oak Wilt and its symptoms, along with an introduction to its transmission. The article noted that there is much confusion and misinformation regarding Oak Wilt, and research goes only so far in providing the answers to important questions. Future research will likely change current recommendations — which is a good thing. Early detection and an accurate diagnosis, paired with a solid management plan, are critical to managing the disease successfully. In some cases, there may be a need to develop a management plan for an entire city block or particular part of a community.

Oak Wilt Management/Diagnosis

An Oak Wilt diagnosis can be confirmed in a laboratory by isolating the fungus from diseased tissues. Taking tissue samples is not a simple process and should be left to someone with specific training and experience. Each step of the process must be done properly. Although all the symptoms indicate Oak Wilt is present, lab reports may return as a “negative.” A negative from the lab does not mean the sampled tree is not infected, only that the fungus could not be found in the particular sample provided. Note that “someone with specific training and experience” is typically a consulting arborist, but may also be a forester or Oak Wilt researcher.

Oak Wilt Management/Suppression

Fungal Spore Mat

As previously noted, fungal spore mats form only on species in the Red Oak group and produce a fruity odor that attracts the Nitidulid beetle — believed to be responsible for the overland spread of the disease. As a result, infected and dying red oaks are a greater concern, due to the potential for aiding in the overland spread. There is no evidence that live oaks contribute to the overland spread. The firewood and stumps from removed live oak trees are not a concern.

Since the spore mats have been known to form on stumps and firewood of species in the Red Oak group, infected trees should be promptly removed from the site and chipped, burned or buried. If this is not practical, remove the infected tree’s bark from the soil line up to 2 or 3 feet to help prevent the formation of spore mats. In urban areas, grinding the stump below the soil surface is also recommended.

Avoid storing infected red oak firewood near healthy trees unless it is “seasoned” or completely dried for at least one year. If infected red oak wood must be left on a site, it should be covered with clear plastic and the edges buried in the soil. Avoid purchasing red oak firewood that appears green and not ready to burn. However, burning infected oak firewood of any species will not spread the disease since the heat of the fire will destroy fungal spores.

The disease is most often spread by root-to-root contact. In a dense group of live oaks, Oak Wilt can expand outward to 75 feet or more each year. Trenching between infected and non-infected trees is a method of suppression in a rural setting, but it is difficult and less successful in an urban area due to the number of underground utilities and obstructions.

By comparison, Oak Wilt centers in the DFW area do not appear to be expanding outward as rapidly as centers found in Austin. One theory is that the disease expands more rapidly in communities with indigenous populations of red oak and live oak. These populations have root systems that are more interconnected than an urban forest established primarily by planting new trees. One of the primary indigenous oaks in North Central Texas is post oak (Quercus stellata), which is extremely tolerant of the disease. The same is true for chinquapin oak (Quercus muehlenbergii) and bur oak(Quercus macrocarpa), which should be planted more often for this reason. Are you starting to lose some of your fears yet?

Next month`s article will cover Oak Wilt Management/Pruning. The final article will address Prevention and Treatment. Afterward, we hope to have fewer nervous tree mothers!!

About the author: Steve Houser is a Dallas native with more than 30 years of experience as a consulting arborist. He is the president of Arborilogical Services Inc., “The Experts Your Trees Deserve.”  www.arborilogical.com.

Oak Wilt Management/Pruning

In managing Oak Wilt, the when and how to prune is a “hot potato” issue that certainly requires clarification. Researchers and governmental agencies often develop disease-management recommendations based on what is best for the entire state. They speak to the layperson. Unless you are very knowledgeable on the subject, you are well-served to follow their advice. However, the details of when and how to safely prune a tree in a specific region where a threat of Oak Wilt exists, includes many variables. A few of these variables include the specific condition of a region’s forest — both urban and rural, the ratio of infected trees to healthy trees, or the distance between the location of a healthy tree and the nearest infected tree or trees. As a result, experts around the state tend to develop different local or regional standards, which may conflict with statewide standards. What works in Austin may not work in San Antonio or the DFW area. Are you confused yet?

Steve Houser explains this month’s photo: “Topless trees are indecent.” (See his final pruning tip below.)

Since existing research goes only so far in providing answers, interpretations of how the research should apply to practicing arborists around the state may differ. Add the fact that arborists around the state can be slightlyopinionated, and things can become quite controversial. On second thought, scratch the “slightly” part!

Since articles in this publication are geared toward the general public, and the topic is complex, with varying opinions, it is important to note only the generally accepted standards that help to reduce the spread of Oak Wilt. The standards are currently under review by professionals, researchers, and governmental agencies. They could change. If you are not sure what to do, follow the guidelines below, or consult with someone who has specific training and regional experience in managing Oak Wilt infections.

•  In general, avoid pruning or wounding living tissue on all oaks from February through June.  The exact dates may vary according to regional conditions. Some wounding, such as wind and hail damage, or squirrels chewing on the bark of limbs, is unavoidable. There are legitimate reasons to prune in the spring. Examples include the removal of hazardous limbs for public safety, limbs that do not conform to city clearance standards, and limbs rubbing on a structure.  If pruning is done properly, oaks can be pruned at any time of year.

• Paint pruning cuts or fresh wounds that affect live tissue immediately. This even includes the remaining stump of a tree in the Red Oak group. Use a wound dressing or latex paint. Wound dressings will be addressed in a future article. For now, avoid thick tar paints and apply only a thin layer of material. Without mentioning a product name, one wound dressing is reported to contain more natural products. Note that, with very few exceptions, painting wounds on all other tree species is not recommended.

• If you are unsure of the risk of spreading the disease, good sanitary practices include sterilizing all pruning tools before work begins. Sterilizing materials can include a simple mix of 10 percent chlorine bleach and water. Oil the tools afterward to prevent potential rust accumulation. Commercial materials are also available — or you can use 190-proof alcohols. However, this seems to be a waste of good resources.

• Any debris from trees in the Red Oak group should be chipped, burned, buried, or covered with plastic, as previously noted.

• When pruning, always make proper cuts (see previous article:http://neilsperry.com/articles/2010/09/29/texas-tree-tips.html), and avoid removing more than 20 percent of the foliage in any given year.

• Never “top” any species of shade tree.

Those who are knowledgeable about Oak Wilt may not always appear to be following the standards noted above. However, this should not lead to the conclusion that they are being irresponsible. Their actions may well be justified by research, local conditions and experience.

The simple act of pruning does not create the only opportunity for infection. Wounds created by any source, including lawn mowers and line trimmers, also offer an opportunity for the disease to spread overland. However, the number of oaks that are infected and killed each year from overland transmission is considered minor compared to those infected by root-to-root contact. Are your fears subsiding yet?

On the lighter side: A tree owner calls his arborist to inspect his tree for Oak Wilt, only to be told the tree is infected. When the tree owner says he wants a second opinion, the arborist responds, “OK … your tree is also ugly.”

About the author: Steve Houser is a Dallas native with more than 30 years of experience as a consulting arborist. He is the president of Arborilogical Services Inc., “The Experts Your Trees Deserve.”  www.arborilogical.com.

Oak Wilt is a complex disease. To fully explain its impact on our trees will require several consecutive articles. Conflicting information in public venues adds to the current Oak Wilt confusion and creates anxiety or anger over the potential loss of a favorite tree. If Grandpa planted the tree, or it screens the neighbors or reduces your energy bill, the tree has special value. It is no longer just a renewable resource easily replaced. Best not to mess with a Texan’s trees!

Although Oak Wilt research is somewhat limited, a good understanding of what is known offers some level of comfort. Dr. David Appel, professor of plant pathology and microbiology at Texas A&M University, is recognized as an expert on the subject. His research has been peer reviewed, and his guidance helped to develop the standards covered in this article, along with the help of two other plant pathologists with extensive Oak Wilt experience. The disease is not rampant or terrorizing all our neighborhoods. It was first discovered in the DFW area in 1978. Let’s keep things in perspective and rely on those who have worked with, managed, and tracked the spread of the disease as a career.

Oak Wilt and Its Symptoms

Oak Wilt is a vascular wilt disease of oak trees caused by the fungus Ceratocystis fagacearum. The fungus enters the tree and stops the flow of water as well as elements by plugging the vessels in the vascular system. All species of oaks are susceptible, with some species being somewhat tolerant. Red oaks, both Shumard and Spanish, are highly susceptible to the pathogen. Live oaks (Quercus fusiformis and Quercus virginiana) follow as a close second. Oaks in the white oak family such as bur oak (Quercus macrocarpa) or chinquapin oak (Quercus muehlenbergii), are more tolerant of an infection.

In the red oak family, the disease expresses itself in two primary ways. The first symptom is an oily green appearance in sections of the tree’s canopy, which rapidly turns a tan or red color. The second, and less common, expression is a heavy and rapid shedding of foliage with individual leaves displaying the symptoms previously mentioned. Infected red oaks typically die within a few months of infection.

Infected live oaks display a variety of foliar symptoms. The most common is called veinal necrosis, a yellowing/browning of the leaf midrib and side veins.

Affected foliage usually drops as this symptom appears, but it is common for some foliage to remain on the tree. Defoliation of live oak trees can occur at any time of the year, but should not be confused with the normal process of leaf-drop and flowering that generally occurs in February and March. Live oaks typically die within six months of infection, with some individuals not dying for years. Advanced training is required to accurately diagnose and properly treat the disease. Uneducated advice can be very costly.

Oak Wilt Transmission

Oak Wilt most frequently spreads from tree to tree by root-to-root contact. Live oaks regularly form functional root grafts with other live oaks. Red oaks appear to form these grafts as well. Oaks like to be “hooked-up” with each other and swap spit. Kidding aside, once the pathogen has entered one tree, it has the potential to move from tree to tree quite readily and efficiently. Root grafting is known to occur between live oaks and red oaks. This phenomenon is not common, but research indicates the potential exists.

Although infrequent, a second method of disease transmission is by overland spread. This occurs when fungal spore mats are produced on a dying red oak and visited by the suspected insect vector or transmitter, the sap-feeding nitidulid beetle. The beetle can carry the spores to a wound on a nearby tree but the spores can infect the tree only if the wound is fresh and created in the previous 24 to 48 hours. All oaks, including live oaks and species in the red oak family, can be infected by overland spread or root-to-root contact.

It should be noted that fungal mats are produced primarily in the spring or cooler times of the year, and only on infected red oaks in a particular stage of decline. Fungal mats are viable, that is producing spores, for a short period — usually two to three weeks at most. Although new infection centers do form, it is not fully understood whether it is from the insect spreading the disease or other methods of transmission not yet discovered or researched.

If you have questions, remember there is more to follow next month on this thrilling subject!

About the author: Steve Houser is a Dallas native with more than 30 years of experience as a consulting arborist. He is the president of Arborilogical Services Inc., “The Experts Your Trees Deserve.” www.arborilogical.com.

Oak wilt is caused by a fungus (Ceratocystis fagacearum) which colonizes the vascular system of the tree.  Conduction of water is disrupted causing the leaves to wilt and ultimately for the tree to die.  The disease is highly virulent and spreads in two (2) known ways.  Trees which have formed root grafts with infected trees may themselves become infected through root graft transmission.  For this reason entire stands of Oak forests may be destroyed over a period of time.  New Oak wilt infection centers may begin when a small sap feeding beetle (aka Nitidulid) visits a spore mat on an infected Red Oak.  (Live Oaks do not produce spore mats).  Once the insect has visited a spore mat, his body may carry the fungal spores to a fresh wound, thus creating a new Oak wilt center infection.  The sap feeding beetles are attracted to feed on the sap which oozes from fresh wounds on trees.  Sap feeding beetle activity, spore formation and tree susceptibility are all at high levels from February to June.  For these reasons the Oak wilt control strategy involves the following recommendations:

1. Avoid pruning mid February – mid June (Red Oaks and Live Oaks).
2. If you must prune during this time, paint cuts and wounds as soon as possible after they occur.  The sap flow from wounds usually has stopped within 24-48 hours, therefore, old wounds do not require painting.
3. Healthy trees near Oak wilt infection centers may be treated on a preventable basis with the fungicide “Propaconizol” (aka Alamo).  This fungicide is injected into the tree at the root flares, and can protect trees for up to three (3) years.
4. Once trees have become infected, successful therapeutic treatment with Alamo is possible, however, results vary and most trees will not survive once symptoms develop.
5. Infected trees, particularly Red Oaks, should be removed promptly.  Red Oak firewood may be another means by which the fungus may be transported to new areas.

Additional research is needed to solve the biology regarding the overland transmission of this potentially devastating tree disease.

More information is available concerning Oak wilt through the Texas A&M extension service, the Texas Forest Service

If you have any further questions or suspect you may have Oak wilt please give us a call or fill out a QUICK contact form!

1. It’s time to prune Oaks – especially Live Oaks and Red Oaks.  To avoid the chance of your trees contracting Oak Wilt disease, necessary pruning should be done before February 1, 1995.  The risky and inappropriate time for Oak pruning is February 1 through June 15.  (According to Texas Forest Service).
2. For the best root development, aerification is the key.  Our deep root invigoration process helps considerably with aeration as well as providing your trees with the nutrients required for good growth in our soils.  Fertilization and inspection programs are available.
3. Turf grass and Trees …….. As most of you know, it is extremely difficult to have both beautiful, healthy trees  and a wonderful lawn.  These two types of plants are inherently incompatible.

Trees originated in forests with rich, fertile soils and surface layers covered with decomposing leaves and other organic material.  Yet in many of our landscapes we attempt to grow trees in compacted, disturbed soils with aggressive turf grass competition over the entire root zone.  This competition with grass along with the absence of a humus layer, restricts the development of the absorbing fine roots.  Further, mowing and weed management also lead to tree problems; mechanical bark damage from line trimmers and mowers, as well as the use of herbicides, can cause severe damage to trees whose roots are within the treated area.  Although herbicides that can cause tree damage have precautionary statements on their labels, most applicators do not realize that tree roots extend 2-3 times the branch system.  Therefore, herbicide injury is a frequent occurrence.  Trees cause problems for the grass.  Excessive shade limits photosynthesis and the subsequent production of carbohydrates necessary for turf growth.  Most turf grasses do well in full sun, may tolerate partial shade, and barely survive in heavy shade.

SOLUTIONS:

The most effective strategy to improve conditions for trees is to maintain large, mulched areas around them.  Eliminate grass and use mulch.  A shade tolerant ground cover such as Vinca, English Ivy, Moneywort, or others, can then be introduced into the mulched area, if desired.

For small trees the mulch area should extend to the drip line.  Dramatic growth response can be expected because the mulch improves aeration in the upper portions of the soil, improves water retention and moderates soil temperatures, further, as the mulch decomposes, nutrients become available to the tree.

Tree-Turf conflicts will always be with us, however, beautiful landscapes are attainable if we use the right plants in locations and environments in which they are best suited.

Although the deciduous trees have lost their leaves for the winter and we humans consider the trees to be dormant, physiologically the tree is very active.  New roots are being developed and the tree is preparing itself for the upcoming spring.  It is important to note that photosynthesis may have stopped when the leaves drop, however, respiration does not.  Respiration is the process where food manufactured in the leaves is burned with oxygen obtained through the roots to provide the energy necessary for growth.

What’s the point?  The past several winters have been extremely wet with the soil saturated for long periods of time resulting in low oxygen levels in the soil and consequently a low rate of respiration.  Many of our tree species which prefer a dry site (Texas Red Oak, Chinquapin Oak, etc.) have experienced some problems related to weakened root systems that I believe to be caused by the excess water and low oxygen levels in the soil.

What can I do?  Although no person can control the weather, each of us can control the use of our irrigation system.  Our clay soil should be allowed to cycle through wet and dry periods.  Prior to irrigation check the soil at a depth of 6 to 8 inches.  If it crumbles, it is time to irrigate.  If it packs into a wet clay ball suitable for making pottery, no irrigation is necessary.  Allowing the soil to dry increases the oxygen content and then the respiration rate.  You will have healthier, stronger plants able to withstand our hot Texas summers, if you irrigate less frequently, but thoroughly saturate the root zone when you do irrigate.  The benefits are stronger roots, healthier plants and a lower water bill.

The dormant season is an excellent time for tree pruning.  Live Oaks and Red Oaks should be pruned at this time or in the heat of summer to cut down on the risk of Oak Wilt disease.  Live Oaks and Red Oaks should not be pruned in the spring.

If you have any questions concerning the health of your trees, please call us.  One of our Certified Arborists will be happy to answer your questions.

THE DISEASE AND ITS BIOLOGY:

Oak Wilt is a vascular wilt disease of Oak trees caused by the fungus Ceratocystis fagacearum. All species of Oaks are susceptible with some species being somewhat tolerant. Red Oaks, both Shumard and Spanish, are highly susceptible to the pathogen with Live Oak following a close second.

The disease in Red Oak is expressed in two primary ways. The first is an oily green appearance to sections of the canopy, which rapidly turn a tan color as the foliage dries on the tree. The other and less common expression is a heavy and rapid shedding of foliage with a variety of the above symptoms on fallen leaves. The shedding is fairly uniform throughout the canopy. There is no effective control for Red Oaks that express active symptoms of infection. However, injection with the fungicide Alamo has proven to be effective as a preventative. Red Oaks properly diagnosed with Oak Wilt should be removed as soon as possible as these species are responsible for the overland spread of the pathogen. There is more and more evidence that Red Oaks infected with the Oak Wilt fungus can be effectively treated if the infection has not progressed too far.

There are a variety of possible foliar symptoms observed in infected Live Oaks. The most common is termed a veinal necrosis or yellowing and browning of the main leaf vein and side veins (see photograph below). The foliage will usually fall once this symptom has appeared. It is possible to see leaves still on the tree with veinal necrosis.The defoliation in Live Oaks can occur at anytime of the year, but should not be confused with the normal process of leaf drop and flowering which generally occurs late February to late March. A small percentage of diseased Live Oaks can potentially be treated with the fungicide injection. However, it should be noted that the curative qualities of the fungicide are limited.

The disease spreads from tree to tree in two methods that we are aware of to date. The first and most common is root to root contact. It is well known that Live Oaks commonly form functional root grafts with other Live Oaks. Red Oaks appear to form these root grafts as well. Once the pathogen has entered a tree, it can potentially move from tree to tree quite readily and efficiently. Less common, but reported to occur, is root grafting between Live Oak and Red Oak. This phenomenon is not nearly as common, but the potential is there. This is why we will commonly recommend to inject all Oaks on the property for protective purposes.

The second method of disease transmission is overland spread. This occurs when fungal mats are produced on dying Red Oaks and visited by the suspected insect vector, the Nitidulid Sap Feeding Beetle.

It should be noted that fungal mats are produced primarily in the Spring or cooler times of the year and only form on Red Oaks, which are at a particular phase of the mortality process. Mats will be viable, that is producing viable spores of the fungus, for a short period of time. This time frame is usually 2 – 3 weeks at the most. Although new infection centers do form from time to time, it is not fully understood whether it is from the insect spreading the disease or possibly other methods of transmission such as infected pruning tools, squirrel damage during the Spring, or methods not yet discovered.

THE ROOT FLARE INJECTION PROCESS:

Oak Wilt

The root flare injection process is three fold. The first is to expose the buttress roots or root flare of the tree or trees being injected. This is accomplished with careful excavation of the base of the tree where plant material and soil are removed from around the base of the tree. The distance away from the trunk in which plant material and soil will need to be removed will vary according to the size or diameter of the tree being treated.

The second step is to physically perform the high volume root flare injection with the registered fungicide “Alamo”. This is the only material registered and labeled for this purpose. It is now available in a water-soluble formulation, which will have a distinct blue color. Anything else being used is ineffective or being illegally applied.

A series of holes will be drilled up and down the exposed root flares at about 4-6 inch increments. Proper location of these injection sites is critical for proper distribution of the fungicide. Inadequate distribution leaves trees poorly protected. A series of injection tees are inserted into the injection sites and connected with tubing to create a closed system. The system is usually attached to a pressure tank containing the fungicide solution and the injection process begins. Once the tree has taken up the allotted amount of fungicide, the system is broken down and removed from the tree.

The third step is to return and fill in the exposed area. There will be many instances where trees have been planted too deep to begin with, or fill soil has been brought in. In these cases we will commonly recommend to fill in with a large stone or leave the root flare exposed entirely. Each situation will differ and your Arborist will recommend what is best for the long-term health of the tree.

In general, Live Oaks and Red Oaks not expressing active disease symptoms are good candidates for preventive root flare injection with the fungicide. It appears that Oaks can be infected with the fungus up to a year before active symptoms are expressed. What this means is that an apparently healthy Oak adjacent to a diseased tree may already be infected and in this instance, uptake of the fungicide may be poor.

COMMONLY ASKED QUESTIONS REGARDING ROOT FLARE INJECTION WITH ALAMO:

Q: Why does the process seem expensive?

A: The cost of the process is primarily driven from the cost of the fungicide. This is dictated by the manufacturer. There is also quite extensive labor involved in properly exposing the root flare of a tree or trees in the injection process itself.

Q: Does it matter how much fungicide the tree receives?

A: It is critical that the tree receives a minimum of 10 milliliters of Alamo for every inch in diameter. This diameter measurement is usually taken about 4.5 feet from soil grade. We will commonly recommend 12 milliliters per inch if infected trees are being injected or high disease pressure exists.

Q: Which trees should I treat?

A: Your Arborist will generally recommend to treat all Oaks on the property, and certainly all that potentially could form root grafts. This will vary from site to site and will usually not include trees already showing active symptoms.

Q: How fast does the disease spread in a population of Oak trees?

A: The disease has been reported to move up to 100 feet per year in a solid stand of Oaks. This can vary greatly due to variables unique to each site.

Q: Should my neighbor treat their trees?

A: The best candidates for preventive injection are those Oaks out ahead of the active disease center. Many times we are called to the property with trees showing active symptoms of Oak Wilt. We ask the fungicide to do much more than it is designed to do when we are always treating trees adjacent to infected trees.

Q: Is this injection process guaranteed?

A: The process has no guarantee. We are however, much more successful when we are treating trees that, number one, are not showing active symptoms. And, number two, are some distance from infected trees. We have had very good results with high volume root flare injection to date. We still see failures from time to time, which is usually due to the tree already being infected which leads to poor uptake and distribution.

Q: Are there alternative methods for the prevention of Oak Wilt?

A: NO, there are currently other types of injection, such as “microinjection” which has no data to date that suggest any type of control or prevention. This process is strictly experimental and will take a number of years to provide adequate data one way or the other. DO NOT LET anyone tell you differently. This can be a confusing point because the manufacturer has packaged Alamo in a microinjection system. This was done primarily to increase revenue for the chemical company and offer what appears to be a quicker and easier method of injection. If an easier method becomes available that is equally successful and cost effective with repeatable results, we will be the first to implement such a method.

Q: If I keep my trees healthy will they be less susceptible to infection by the Oak Wilt fungus?

A: No, it is unfortunate that this is not the case. We are dealing with an aggressive vascular wilt disease and a tree, which is genetically predisposed to infection by the fungus. To draw an analogy, the Chicken Pox Virus does not infect children, which are unhealthy. The healthiest children will still get the infection at some time or another because humans are genetically predisposed to the Chicken Pox Virus.

Q: Will the root flare injection ever need to be repeated?

A: Once trees are injected, it appears they are protected for about 2 years. If disease pressure is high, that is to say the Oak Wilt center is still active next door or across the street, we may recommend to retreat the following year. If we are treating trees with active symptoms and the symptoms reappear the following season, we will commonly recommend to retreat. Retreating high value or unique or historic trees annually as a preventative is not unusual.