At Texas Tree Surgeons, we love trees and we love our customers, and we have created a series of articles covering tree basics. If you have a specific tree question, let us know!

Oak wilt, and the precautions that need to be taken to help prevent the spread of this fungal disease, may be the most often talked-about aspect of tree health care in Texas. Throughout the state, tree owners and communities are challenged by the potential devastation to all species of oak tree. In some areas, there are ordinances in place that restrict oak trimming in order to prevent the spread of the disease. Other areas have no formal regulation, and this can lead to a lack of awareness and a potential for widespread infection.

While oak wilt is a serious threat to our North Texas urban forest, there are simple steps that everyone can take to lessen its impact.

How do trees get oak wilt?

The most common ways for the oak wilt fungus to be transmitted are by insect activity and root grafting. Insects can infect a tree through any exposed wood (not covered by bark) or open wound (such as a pruning cut, broken limb, or where branches rub against each other). In situations with oaks planted in close proximity, the fungus can be transmitted from one tree to another via underground root grafting. As roots make contact with other roots, they grow together and share pathogens.

Different species of oak can contract and spread oak wilt by different methods.

RED OAKS

Red oaks (Texas, Shumard, blackjack, water) are extremely susceptible to infection through insect activity. Red oaks are often the primary mode by which oak wilt gains a foothold in a new area. The oak wilt fungus thrives in red oaks and creates visible fungal mats underneath the bark. These spore mats attract insects; sap beetles of the Nitidulidae family are the most common type. Beetles feed in the infected area and become covered with particles from the spore mats. Drawn to exposed wood on healthy trees, the beetles transfer the fungal spores, spreading the infection.

LIVE OAKS

In contrast to red oaks, live oaks are susceptible to oak wilt primarily through their root systems. In nature, live oaks often grow in groups, sometimes called motts. Underneath the mott, the root systems of the individual trees become interconnected. This grafting allows not only nutrients to be shared, but pathogens as well. Once a member of the mott has contracted the oak wilt fungus, the infection quickly spreads.

WHITE OAKS

White oaks (post, bur, chinkapin) are more resistant to oak wilt than other species, but are still at risk. Transmission generally occurs through spore transfer by insects, or by human activity.

Can you prevent Oak Wilt?

Oak wilt is an epidemic. Because of the concentration and susceptibility of oaks in Texas, especially red oaks, it can be difficult to isolate centers of infection and prevent further spread. The Texas A&M Forest Service and the Forest Health Protection branch of the U.S. Department of Agriculture have issued some guidelines to help prevent further tree death.

• Remove and properly dispose of diseased red oaks immediately
  • Chip or bury all tree material
• Do not transport unseasoned firewood
  • Firewood should be dry, splitting, and the bark should be peeling off
• Do not store unseasoned oak firewood uncovered
  • Cover tightly with heavy, clear plastic and bury the edges to restrict insect access
• Do not prune or otherwise wound oak trees from February 1 to July 1
  • The best time to trim is in the fall and winter
• When infection is a risk, take proper precautions
  • Sterilize tools and paint cuts

If you have healthy oak trees in an area with infected trees, preventative treatment may be effective in slowing transmission. As oak wilt is a systemic, vascular disease, the most effective treatments consist of injecting the infected trees with a fungicidal chemical. The only currently recommended fungicide is Alamo®, a formulation of the fungicide propiconazole. The fungicide is administered through holes drilled in the root flare of the infected tree and should only be applied by Texas Department of Agriculture Licensed Applicators.

For large stands of oak trees, especially live oaks, trenching around the area and severing root connections can limit disease spread, as well.

Can you cure Oak Wilt?

There is no known cure for oak wilt. Reported home remedies or substances applied to the exterior of the tree have not be proven to have any remedial effect. If you have a tree that is infected with oak wilt, be sure to consult a Texas Oak Wilt Qualified arborist or your local Texas A&M Agrilife Extension agent to discuss treatment options.

Red oaks usually defoliate and die one to six months after becoming symptomatic. Live oaks may last up to a few years before total necrosis. White oaks show the most resistance to oak wilt and may survive several years after infection.

Fungicidal treatment may prolong the life of infected trees, but cannot eradicate the disease. However, systemic fungicides are most effective if a tree has not lost more than 30% of the crown. Contact a certified arborist to see if your tree may be a good candidate for treatment.

What areas have Oak Wilt?

In North Texas, there are many centers of infection. At Texas Tree Surgeons, we take oak wilt precautions throughout our service area. Still, there are a few neighborhoods in which we have seen particularly bad oak wilt activity:

• Preston Hollow, Dallas
• Lakewood, Dallas
• Walnut Hill and Abrams, Dallas
• Coit and Campbell, Richardson
• President George Bush Turnpike and the Tollway, North Dallas
• Park and US 75 in Plano
• Highland Park
• University Park

If you live in one of these areas, or suspect oak wilt activity in your neighborhood, contact your arborist to see what specific preventative steps are recommended for your trees.

Oak wilt is one of the greatest threats to trees in Texas. Education, awareness, and prevention are the best tools we have to protect our urban forest from devastation. If you want to learn more about oak wilt, visit TexasOakWilt.org.

At Texas Tree Surgeons, we love trees and we love our customers, and we believe that the more people learn about their trees, the better we can serve our community. We have several Oak Wilt Qualified arborists on staff; please let us know if you have any questions about oak wilt or any other tree question. We are always happy to help!

* – Until 2017, the oak wilt fungus was identified as Ceratocystis fagacearum.

Another installment in our series of posts where Texas Tree Surgeons answers your tree questions. Are you having problems with your trees and want to know what’s wrong? Let us know!

Dear Texas Tree Surgeons,

I’ve been hearing about the emerald ash borer, and it seems pretty serious; should I be worried?

-J.G.

You may have seen recent media coverage of the discovery of the emerald ash borer (“EAB”) in Texas. The emerald ash borer (Agrilus planipennis) is a small, green beetle that feeds on ash trees. Though native to Asia, EAB first appeared in North America in 2002. In 2016, EAB was found in northeast Texas. In July 2017, suspected EAB specimens were found in Tarrant County. In early December 2018, the Texas A&M Forest Service confirmed that several ash trees near Eagle Mountain Lake had been killed by EAB infestation. In May 2020, Texas A&M confirmed presence of EAB in the Denton area.

Should I be Concerned About Emerald Ash Borer?

The threat from EAB is a serious one, as ash trees make up between 5-13% of the DFW urban forest, and are important providers of shade and clean air. If you do have ash trees, however, EAB infestation can be prevented.

Emerald Ash Borer Prevention Tips

• If there are diseased or damaged ash trees, consider removal before they have a chance to be infested.
• If there is EAB activity within a few miles, consider preventative systemic insecticide treatment.
• Keep an eye out for signs of EAB activity:
  • Dead/dying branches in upper crown
  • Shoots/suckers along trunk
  • Splitting bark with insect trails underneath
  • Increased woodpecker activity
  • D-shaped exit holes

Can Emerald Ash Borer be Treated?

Unfortunately, once an ash tree has been infested by EAB, there is little that can be done. Insecticide treatments can help slow the decline of the tree, but once more than 50% of the canopy is gone, treatments are not effective. EAB generally kills infested trees in two to five years.

So, yes, the emerald ash borer is a serious threat to ash trees, but education and awareness now can help mitigate its effects. If you have ash trees, take note of their appearance, and contact your arborist if you see any signs of decline. If you don’t have any ash trees, you do not need to worry about EAB at all.

For more information on EAB, visit the Texas A&M Forest Service. For help identifying your trees, visit Trees of Texas.

At Texas Tree Surgeons, we love trees and we love our community! The spread of emerald ash borer, while a threat to a small percentage of North Texas trees, is a threat that we can all help to fight against. If you have ash trees or know someone who does, let us know, and one of our ISA Certified Arborists will be happy to evaluate the trees for EAB risk factors and provide options to keep them safe and healthy.

While many plant and tree diseases are commonly seen and can be accurately diagnosed by visual inspection, there are cases where further testing is required. In Texas, the Texas A&M AgriLife Extension Service runs the Texas Plant Disease Diagnostic Laboratory, which is tasked with analyzing plant samples sent in from all over the state. When there is a question as to the particular pathogen affecting a tree, or when further treatment recommendations are needed, we advise our customers to submit a sample to the TPDDL.

The process of sample submission can appear daunting at first, but is actually fairly simple. There are three main steps:

1. Collecting a sample
2. Completing the form
3. Packaging and shipping

1. Collecting a Sample

When collecting a sample for submission, there are a few guidelines that should be followed. In general, it is important to get a live sample, if possible. Clip off the part of the tree that is showing the worst symptoms, like the ends of branches with leaves attached. If there is a potential for root contamination, dig up a few small roots from near the tree trunk, along with some of the surrounding soil. For fruiting or flowering trees, be sure to get some not-yet-fallen blossoms or fruit, if they are showing signs of an issue, as well.

Certain diseases, such as Oak Wilt or Dutch Elm Disease, require specific sample types. The TPDDL submission form has instructions for these cases. 

2. Completing the Form

Filling out a form may not seem like a challenge, but for those unfamiliar with the TPDDL diagnostic process, there may be some information that needs to be gathered beforehand. Additionally, we have a few tips and recommendations to avoid confusion and get the most benefit out of the TPDDL analysis.

Click here to download a copy of the form as a PDF. There are instructions on the second page, and some helpful descriptions below.

3. Packaging and Shipping

It is critical to pack and ship your sample appropriately, to enable the TPDDL to conduct their analysis. Certain samples require special preparations, but for most submissions, all you need are some zip-top bags and basic packing material.

• Send live samples only.
  • If the sample cannot be sent immediately after collection, be sure to keep it refrigerated.
• Pack each sample type in a separate plastic bag.
  • Any soil or roots should be kept separate from leaves/branches and fruits/flowers.
• Do not put anything else in the sample bags.
  • Do not put any excess moisture, paper towls, or submission forms.
• Enclose submission forms in a separate plastic bag.
  • This helps keep the forms from getting damaged by sample leakage.
• Pack all materials in a sturdy shipping box.
  • Do not use only an envelope, as the samples may be damaged.
  • Use recycled newspaper if you need extra padding.
• Use expedited shipping if possible.
  • The TPDDL is open during normal business hours, Monday-Friday; consult their website for any scheduled closures.
  • Overnight shipping is usually the best option.

When Should I Expect My Results?

Depending on the season, results can come in as little as two weeks, but may take longer. The fall and spring are high submission times, and can lead to some delays. Additionally, certain tests take time to perform. If you have any questions about specifc turnaround time, contact the TPDDL.

What Will I Get Back from the Lab?

Once the testing is complete, you will receive a results report in the way you indicated on the form. You will not receive any of the samples or packing materials back. The results form indicates what tests were done, what the findings were, and what management steps are recommended.

Click here for a sample results report, and see the explanations below.

What do I do now?

The TPDDL testing results and recommendations will give you a starting point for managing a sick of stressed tree. Some steps, such as modifying watering schedules, need to be undertaken by the tree owner. Others, such as application of recommended pesticides, must be performed by a licensed professional. Once you have your results from the lab, contact a certified arborist to discuss the best way to proceed.

At Texas Tree Surgeons, we love trees and we love our customers, and we believe that the more people learn about their trees, the better we can serve our community. We hope this article has helped answer your questions about stump grinding and what your options might be. If you have any specific questions, let us know, and we’ll be happy to send an arborist out to evaluate your needs and offer our suggestions and expertise.

At Texas Tree Surgeons, we love trees and we love our customers, and we have created a series of articles covering tree basics. If you have a specific tree question, let us know!

Mulch is an important part of tree care that is often overlooked. Many trees are surrounded by turf grass or other plants, which can stifle their growth. Proper mulching can be the key to trees that not just survive, but thrive.

In nature, trees live in a complex organic environment. A forest can be made up of hundreds of different plant and animal species, each contributing something to its surroundings. The forest floor is composed of layers of organic material, from fallen and rotting trees to tiny plants that serve as ground cover. This complexity provides a habitat for animals, plants, and microorganisms. In this environment, a tree is able to send out its roots into rich, fertile soil and get the exact nutrients it needs to thrive.

In our urban environment, trees are often in competition for resources with turf grass.  or may even be surrounded by non-organic materials, such as concrete. The soil around a tree can easily become compacted due to above-ground traffic. While we cannot completely re-create the forest environment in a city, we can help reduce soil compaction and competition by correctly mulching around trees. When mulch is properly applied and maintained, trees are able to grow sturdier root structures, tree health is improved, and we benefit from hardier trees that can live for decades.

Does the Type of Mulch Matter?

Despite the various ways that mulch is marketed, packaged, and sold, there are only two basic types: organic and inorganic. Organic mulch is made up of plant material, and can come from a variety of sources. Wood chips, bark, nut shells, and pine needles are common components. Inorganic mulch includes anything that is not plant or animal material and does not break down naturally. Crushed stone, recycled tires, and landscape fabric are common types. While inorganic materials can be useful in certain landscaping applications, they are not beneficial to trees, and may actually be harmful if used as tree mulch.

Choosing the best mulch requires understanding the needs of your tree and the underlying soil conditions. Soil density, pH, drainage, and composition all have an effect on the ability of a tree to send out roots and get the nutrients it requires. While mulch is not primarily a fertilizer, it is composed of organic matter. Insects, earthworms, and microorganisms break down the organic material become food for the tree. Mulch selection and maintenance can influence which types of organisms are able to survive in the mulched area and benefit (or harm) the tree.

Most commercially-available mulch is made from tree material that is shredded to a consistent size, partially composted, and often dyed brown, black, or red. Commercial mulch is generally long-lasting and a good basic mulch. We recommend sourcing mulch from a reliable local producer that does not use chemical treatments or dyes, but composts mulch naturally.

In addition to general-purpose mulch, many producers offer mulch produced from a particular material, which can be used to alter or amend the chemical composition of the soil. Pine bark, for example, is acidic, and cedar mulch contains cedar oil, which can be a natural insect repellent. Other materials, such as nut shells or pine needles, may be available and can be helpful when mulching a particular species. Contact your arborist to see about mulch producers in your area/

Can I Use Wood Chips or Grass Clippings as Mulch?

Tree care businesses or municipalities may sell wood chips produced as a waste product of tree trimming or removal. If you have tree work performed, the tree trimmers may leave wood chips behind. These chips can be a cost-effective way to get organic material, but are not identical to commercially-produced mulch. Best practice is to compost any fresh wood chips before using.

Grass clippings, leaves, and other landscape waste material should be thoroughly composted before use to help prevent weed growth and neutralize any chemical imbalances. Sawdust should likewise be composted first, but sawdust from treated lumber should never be used as mulch. If modifications to soil pH are recommended, certain materials can be added uncomposted to mulch to achieve the desired effect. Ask your arborist for any special needs your trees may have.

The Right Mulch for You

In North Texas, it is common to have fairly dense, clay-like soil that tends to be more alkaline than acidic. Ensuring good drainage during wet weather can be difficult. In dryer periods, the soil can harden and crack. Mulch can help create a stable, permeable layer that can regulate moisture better than the underlying soil. Mulch also insulates the shallow roots from swings in temperature that we can have during the spring and fall. Most native trees and shrubs are adapted to the natural soil pH and composition, and only need basic mulching. Other species, however, may benefit from slightly acidic mulch.

At Texas Tree Surgeons, we love trees and we love our customers, and we believe that the more people learn about their trees, the better we can serve our community. We hope this article has helped answer your questions about mulch. If you have any specific questions, let us know, and we’ll be happy to send an arborist out to evaluate your needs and offer our suggestions and expertise.

-K.N.

As we’ve mentioned before, all this rain has really been a mixed blessing. While we are happy to be safely out of drought conditions, many issues that we don’t see in drier weather have started presenting themselves. Fungi, which thrive in moist environments, have been growing rapidly, sometimes seeming to appear overnight. While a few toadstools in your yard may not indicate a serious problem, visible fungal growth on trees is something to be on the lookout for and may need to be addressed.

There are a wide variety of different fungal species that can live in the soil around trees. Some are beneficial, and are part of a healthy soil ecosystem. Others, however, can spread through a tree’s living tissue and cause health problems for the tree. We have seen problems with Chinese pistaches recently that are caused by a proliferation of fungi due to the wet weather. In the past few years, Italian cypresses have also been afflicted with health issues due to the spreading of a particular fungus. In both these cases, there were little or no warning signs or visible “mushroom” growth before the trees started browning and dying back. However, there are some fungal infections that exhibit visible growths and can be diagnosed before the tree is too far gone.

Ganoderma

Ganoderma is the name of a genus of fungi, and there are several different species that are present in the environment. While the different species vary in appearance, the ones commonly seen in North Texas generally mature into ear-shaped growths called “conks.” The conks may appear on a tree trunk, near the base, or even grow right out of the ground. The conks begin as white- or light-colored, but darken into dark orange or brown with a shiny appearance on top. Oaks and elms are particularly susceptible to Ganoderma, but other species can become infected, as well.

Ganoderma, like Kretzschmaria, is present in the soil, and infects a tree when its roots become damaged and lose their protective bark. While Ganoderma is similarly untreatable, it can be easier to detect in its early stages and may be able to be managed, avoiding immediate removal. Root zone excavation can also be helpful in determining the extent of damage.

ARE ALL MUSHROOMS BAD?

While Kretzschmaria and Ganoderma can cause serious tree stability and health problems, not all visible fungi are a hazard. Fungi in the genus Laetiporus (such as sulfur shelf or chicken of the woods mushrooms) can live on a tree trunk for years without harming the tree. Common white toadstools, such as those in the genus Lepiota, may appear in lawns as a result of beneficial fungal growth in the soil. In periods of heavy rain, species that are usually hidden underground may show visible growths. If you see mushrooms or other fungal growth in your yard or on your tree, send us a photo, and we are happy to let you know if it’s something to be worried about. We love trees and we love our customers, and we always want to help you understand the complex ecology of our urban forest.

Have a specific tree question? Let us know, and you may see it answered in a future Ask Texas Tree Surgeons installment!