The emerald ash borer (EAB) is an invasive, wood-boring beetle. It was first discovered in the United States in southeastern Michigan in 2002. Experts believe the pest entered the country on solid wood packing material originating from Asia. Since its discovery, the emerald ash borer has killed millions of ash trees in North America. EAB was first confirmed in Texas on May 6, 2016, in Harrison County. It has since spread across the state, with confirmed infestations in Dallas and Denton counties. As of 2024, EAB has moved south and was recently confirmed in 5 new Texas counties. **If you have an ash tree on your property, you MUST treat for emerald ash borer every 2 years.** Otherwise, the tree should be removed and replaced with a regionally appropriate species. ## What does EAB do to ash trees? The larval stage of the borer feeds on the inner bark of ash trees, preventing the tree from transporting nutrients and water. Larvae actively feed from the early summer through the fall. Infested ash trees become stressed and decline quickly—most die within 2–3 years of initial infestation. Ash trees killed by EAB are brittle and structurally compromised, making them much more susceptible to damage caused by high winds and storms. Additionally, they are extremely dangerous to remove through conventional methods and may require costly crane removal. ## Signs and Symptoms of EAB - **Canopy dieback:** Begins in the top third of the canopy, continues until the infested tree is bare. - **Epicormic shoots:** New shoot growth proceeding from the bark of infested trees, usually found in the roots or on the trunk. The leaves from these shoots may be larger than usual. - **Bark splitting**: Vertical ruptures in the outer bark, often exposing larval feeding galleries underneath; splitting caused by host tree forming woundwood in response to larval feeding activity. - **D-shaped exit wounds:** Caused by adult beetles emerging from the bark of infested ash trees. - **Serpentine larval feeding galleries**: Found in the inner bark of infested ash trees. - **Increased woodpecker activity and damage:** Due to woodpeckers feeding on EAB larvae. ## How is EAB transmitted? Emerald ash borer, like other wood pests, may be spread when infested ash trees, logs, or firewood are moved from a quarantine zone. This may spread EAB to different regions or even between states. When the mature beetles emerge from the ash tree in June, they spread within the infested region by laying eggs inside nearby ash trees. Adult emerald ash beetles can fly at least 1/2 mile from their home tree. ## Treating EAB The most effective treatment for EAB is preventative. Treatment involves applying an insecticide to the ash tree via trunk injection. The best time to treat for EAB is in the spring while the larvae are still young and unestablished. If EAB has been detected by the presence of symptoms, the infested tree has most likely sustained significant damage. At that point, it may not be feasible to treat the infestation. Instead, the infested ash tree should be removed and destroyed in accordance with state and federal guidelines.

Oak wilt is a fungal disease affecting oak trees. The fungus grows and spreads throughout the tree’s vascular system, depriving the host of nutrients and water. The presence of the pathogen triggers an immune response from the host tree which further blocks the movement of water. These two symptoms effectively choke the oak tree until it begins to wilt and die. ## How is Oak Wilt Transmitted? The fungus responsible for oak wilt—*Bretziella fagacearum*—is primarily spread in two ways. First, oak wilt may be transmitted over long distances by sap-feeding beetles, commonly known as picnic beetles. These beetles feed on the spore mats of diseased oak trees. The beetles then carry the spores with them to feed on the sap from a fresh tree wound, such as a pruning cut. Second, oak wilt may be transmitted by root grafting. When two trees of the same species grow in close proximity to one another, their roots will graft together and fuse, much like a skin graft. If either tree is infected, the pathogen may spread to the other. This is why oak wilt is a problem if it is present in your neighborhood. ## Preventing Oak Wilt The most important step to prevent oak wilt is to avoid wounding your oak tree when conditions are favorable for transmission. According to the Texas Forest Service, you should avoid pruning oak trees from February 1 to June 30. If it is necessary to prune or otherwise wound an oak tree in that time, a pruning sealer should immediately be applied to the wound. If oak wilt has been identified in your neighborhood, preventative oak wilt injections may protect your oak trees from the disease. The fungicide spreads throughout the vascular system of the tree, preventing the pathogen from taking root. The Texas Forest Service recommends injecting high-value oak trees that are within 75–100 ft. of a symptomatic host tree. Susceptibility to the disease varies by species. While white oaks are generally resistant to oak wilt, red oaks are very susceptible to the disease and may die within months or even weeks of infection. Live oaks lie somewhere in the middle: some die within a few months, others die in 1–2 years, and a few (about 1/10) are infected but never succumb to the disease. ## Treating Oak Wilt If your oak tree becomes infected, it is possible to perform therapeutic injections. This involves injecting the symptomatic tree with fungicide to slow and hopefully stop the development of oak wilt in that tree. The best results are achieved if no more than 30% of the canopy is showing symptoms of oak wilt. If more than 30% of the canopy is symptomatic, it is unlikely that therapeutic injections will be effective.

Just like us, trees can suffer lasting damage from exposure to the sun and intense heat. Sunburn affects leaves, with discoloration and damage showing after sudden or intense exposure. Sunscald is a sun-induced injury to the bark—usually on the south or southwest side of young, thin-barked trunks. Species often afflicted include: maples (Japanese, red, and hybrids), ash, honeylocust, sweetgum, red oaks, pecans, elms, hollies, and magnolias. Both sunburn and sunscald are caused by exposure to intense light and heat. Changes in the landscape, such as limb loss or tree removals, can abruptly increase sun on parts of a tree that were previously shaded. The heat may be further intensified and reflected by nearby walls or pavement. Exposed to extreme heat and lacking insulation, the bark of young or thin-barked trees may die and later slough off. ## Symptoms of Sunburn & Sunscald *Foliage (sunburn):* Affected leaves first look washed-out or bleached, then redden. Overlapping leaves can make distinct “shadow” patterns. The sunburn may looking patchy in the canopy due to the changing light conditions throughout the day. Foliar sunburn frequently follows the path of the sun. For the same reason, sunburn is found most often in the south or southwest side of the landscape. *Bark (sunscald):* The early signs of sunscald are subtle: discolored bark and small vertical cracks. Bleeding may appear in the spring. Later, long vertical fissures form as dead bark peels away. Large wounds weaken the trunk and can contribute to future failure. ## Prevention The best way to prevent long-term sun damage to your trees is to improve the environmental conditions and cultural practices of your landscape. These measures are intended to reduce stress and avoid aggravating injuries. - Leave adequate lower branches on newly planted trees for a few years to shade the trunk. - Limit drastic canopy thinning. - Where possible, provide shade from the south/west with nearby plantings or a light-colored board/fence. - Reduce reflected heat from hardscape. - Keep trees evenly watered during prolonged heat/drought - Maintain a 2–4 in. organic mulch ring (not piled on the trunk). ## Management ### Sunscald (on the trunk) Sunscald may be managed with trunk wraps. Use **light-colored** wraps, such as kraft paper or breathable white fabric. **Do not** use dark materials; they intensify heating. Wrap without constricting the trunk, especially where it flares out near the base. Leave shading materials in place until the bark thickens or the canopy shades the trunk. Some practitioners use diluted white latex paint on lower trunks to reflect sunlight. We don’t recommend this as it can be difficult to make sure your paint is plant-safe. If damage has already occurred, watch the afflicted area over time—large, long fissures indicate structural weakness and may justify risk assessment or support. ### Sunburn (on the leaves) Proper irrigation and mulching can help the tree cope with extreme heat. Avoid fertilizing in hot periods, as this will stimulate tender growth which is ill-equipped to contend with extreme heat. For high-value plants, short-term shade cloth can limit sunburn during extreme heat, although it is visually obtrusive.

Cotton root rot (CRR) is soilborne fungal disease that attacks the roots of susceptible plants. Without functioning roots, the host cannot take up water, resulting in rapid decline and death. It is also called “Texas root rot” because of its prevalence in Texas, although it is common throughout the southwestern United States. The disease is called cotton root rot because it is frequently found on cotton. Cotton is a woody plant that is closely related to trees and shrubs. As a consequence, CRR has a very wide host range, affecting more than 2000 plants. Members of the _Rosacae_ family, such as Bradford pears and photinias, are especially susceptible. ## The Disease Triangle and Cotton Root Rot One of the fundamental models we use in plant science is the disease triangle. It illustrates the interaction between the three factors necessary for disease: a susceptible host, the presence of a pathogen, and favorable environmental conditions. When these three elements converge, disease can occur. Like with [take-all root rot (TARR)](https://samhilltreecare.com/resources/take-all-root-rot), understanding the disease triangle can help us better understand and combat cotton root rot. ### Susceptible Host As mentioned earlier, cotton root rot has a very wide range of hosts—more than 2000 different plants. Members of the _Rosacae_ family are especially susceptible. ### Presence of the Pathogen Cotton root rot is very common in North Texas soils. The fungal pathogen responsible for CRR, _Phymatotrichum omnivorum,_ makes ball-like reproductive structures (called sclerotia) known to persist in the soil for up to 50 years. Because large swaths of our land were once used for cotton farming, the soil in even many residential areas still contain the sclerotia from past CRR infections. ### Favorable Environment Cotton root rot flourishes in high temperatures, alkaline conditions, and excess moisture. Unfortunately, these exact conditions are found all over Dallas. Our soils are clay-heavy and drain poorly. They are also calcareous (high in calcium), making them relatively alkaline (pH 7.8–8.2 on average). ## Signs of Cotton Root Rot Because it kills the host so quickly, diagnosing CRR is often a post-mortem. The diagnostic symptom is cinnamon colored strands (called rhizomorphs) on the roots of the host. These strands are needlepoint-like and crossed. During warm, rainy weather, the pathogen may form spore mats on the soil surface, like those depicted in the picture above. ## Treating Cotton Root Rot Unfortunately, little can be done to treat cotton root rot aside from amending the soil to lower the pH. If the host has died and must be removed, be sure to replant with a more resistant species. Some experimental fungicides have shown promise and may prove useful in the future, but they are not available commercially as of yet.

Dutch elm disease is a serious fungal disease affecting elm trees. The disease was first introduced to North America in 1928 on imported timber. It is principally caused by two related fungi, _Ophiostoma ulmi_ and _Ophiostoma novo-ulmi._ Dutch elm disease typically spreads in one of two ways: 1. Elm bark beetles may carry the fungal spores between susceptible hosts at some distance. 2. Neighboring elm trees may form root grafts through which the fungus may spread. The introduction of Dutch elm disease led to a massive epidemic in the elm trees of North America. The disease killed off a huge swath of American elm trees in the mid-twentieth century. Americans elms (_Ulmus americana_) were once a nearly ubiquitous species. Favored for their ability to form a neat, closed canopy, the American elm was a popular choice for planting along city streets. They are now a rarity in many parts of the country they once dominated. ## Dutch Elm Disease in Texas Dutch elm disease is an ongoing problem in the Northeastern and Midwestern United States. It is comparatively less common in Texas. Some speculate that Dutch elm disease may be less common here because the pathogen is sensitive to heat. This theory aligns with our experience—we see infections flare up most when temperatures are mild. Dutch elm disease is also gaining a foothold in some pockets of north Texas. In particular, most infections are concentrated in the Mid-Cities region; there have been confirmed infections in Murphy, Sachse, Flower Mound, and Grapevine. ## Symptoms of Dutch Elm Disease Similar to oak wilt, the fungal spores spread throughout the vascular system of the tree. In an attempt to stop the spreading pathogen, the tree plugs the water-carrying vessels with balloon-like structures called tyloses. Unfortunately, this immune response does not occur quickly enough in susceptible species. The response is actually counter-productive. Rather than containing the fungi, the tree loses its ability to transport water up the trunk. In Texas, the symptoms of Dutch elm disease are most visible when temperatures begin to rise—from mid-May to early June. The leaves on the outer crown wilt and turn yellow. Eventually they turn brown and may be shed from the tree. As the infection progresses, the yellowing and wilting advances along the infected branches from the outer crown down toward the trunk. Another symptom of Dutch elm disease is brown streaks running lengthwise along the sapwood of wilted branches. This symptom is often missed because the bark must be removed in order to observe it. Properly diagnosing Dutch elm disease can be tricky. In our climate, heat and water stress are common concerns. For this reason, Dutch elm disease may be mistaken for a lack of sufficient water. Positive diagnosis typically involves sending a branch sample to a plant diagnostic clinic. ## Treating Dutch Elm Disease Preventative treatments are the most effective way to lower the risk of Dutch elm disease. If you live in a pocket of infections, such as the Mid-Cities, it's important to monitor your landscape and neighborhood for signs of Dutch elm disease. If the disease is a recurring problem in your area, consider preventative treatments every 1–3 years. When branches start flagging due to wilt, we can begin "bark tracing" to remove infected tissue and, hopefully, contain the spread of the disease. Root grafts should also be broken by trenching in order to prevent the disease from spreading to neighboring elm trees. If symptoms have progressed and management is no longer possible, the infected tree should be removed and properly disposed of. ## Additional Resources The University of Minnesota Extension has a [great general factsheet](https://extension.umn.edu/plant-diseases/dutch-elm-disease) on Dutch elm disease. Minneapolis–Saint Paul still has a vibrant population of American elms in what would otherwise be a hotbed of infections. This is largely due to their excellent management strategies at the community level. David N. Appel, Professor Emeritus in the Department of Plant Pathology & Microbiology at Texas A&M, wrote an excellent [primer on Dutch elm disease in Texas](https://www.texasinvasives.org/resources/publications/DUTCH_ELM_DISEASE_Appel.pdf) some years ago. He discusses the nuances of the disease in Texas specifically.

The emerald ash borer (EAB) is an invasive, wood-boring beetle. It was first discovered in the United States in southeastern Michigan in 2002. Experts believe the pest entered the country on solid wood packing material originating from Asia. Since its discovery, the emerald ash borer has killed millions of ash trees in North America. EAB was first confirmed in Texas on May 6, 2016, in Harrison County. It has since spread across the state, with confirmed infestations in Dallas and Denton counties. As of 2024, EAB has moved south and was recently confirmed in 5 new Texas counties. **If you have an ash tree on your property, you MUST treat for emerald ash borer every 2 years.** Otherwise, the tree should be removed and replaced with a regionally appropriate species. ## What does EAB do to ash trees? The larval stage of the borer feeds on the inner bark of ash trees, preventing the tree from transporting nutrients and water. Larvae actively feed from the early summer through the fall. Infested ash trees become stressed and decline quickly—most die within 2–3 years of initial infestation. Ash trees killed by EAB are brittle and structurally compromised, making them much more susceptible to damage caused by high winds and storms. Additionally, they are extremely dangerous to remove through conventional methods and may require costly crane removal. ## Signs and Symptoms of EAB - **Canopy dieback:** Begins in the top third of the canopy, continues until the infested tree is bare. - **Epicormic shoots:** New shoot growth proceeding from the bark of infested trees, usually found in the roots or on the trunk. The leaves from these shoots may be larger than usual. - **Bark splitting**: Vertical ruptures in the outer bark, often exposing larval feeding galleries underneath; splitting caused by host tree forming woundwood in response to larval feeding activity. - **D-shaped exit wounds:** Caused by adult beetles emerging from the bark of infested ash trees. - **Serpentine larval feeding galleries**: Found in the inner bark of infested ash trees. - **Increased woodpecker activity and damage:** Due to woodpeckers feeding on EAB larvae. ## How is EAB transmitted? Emerald ash borer, like other wood pests, may be spread when infested ash trees, logs, or firewood are moved from a quarantine zone. This may spread EAB to different regions or even between states. When the mature beetles emerge from the ash tree in June, they spread within the infested region by laying eggs inside nearby ash trees. Adult emerald ash beetles can fly at least 1/2 mile from their home tree. ## Treating EAB The most effective treatment for EAB is preventative. Treatment involves applying an insecticide to the ash tree via trunk injection. The best time to treat for EAB is in the spring while the larvae are still young and unestablished. If EAB has been detected by the presence of symptoms, the infested tree has most likely sustained significant damage. At that point, it may not be feasible to treat the infestation. Instead, the infested ash tree should be removed and destroyed in accordance with state and federal guidelines.

Developmental pruning, also known as young tree pruning, is the process of pruning young trees to develop good structure while they are still young. This type of pruning can pay dividends for generations, as one of the main ways that a tree dies prematurely is structural failure. Structural pruning practices were largely developed by Dr. Ed Gilman, emeritus professor at the University of Florida. Dr. Gilman has worked closely with Sam Hill Tree Care. He led several training sessions with our team, sharing his expertise on the intricacies of structural pruning. ## Why is Developmental Pruning Performed? Developmental pruning is performed to mimic the structure that trees develop in their natural environment. Most trees grow in forests and compete with neighboring trees for sunlight. For this reason, forest trees typically develop a single dominant trunk (called a "leader") that is tall and straight. In the absence of this competition, landscape trees are encouraged to grow horizontally rather than vertically. The resulting structure—a short, wide canopy with multiple competing leaders—is weak and prone to failure. Developmental pruning should begin as soon as possible to promote good structure. Ideally, the nursery will begin developing good structure before the tree even reaches your landscape, but unfortunately, this practice is not widespread among Texas nurseries.[^1] Developmental pruning is especially cost-effective when done in the early stages of a tree's life. Although structure can still be improved with later correction, it is more costly and rarely yields equivalent results. [^1]: Florida, home of structural pruning pioneer Dr. Ed Gilman, developed the Florida Grades and Standards for Nursery Plants in 2015. Nurseries may only sell trees graded Florida #1 or higher, so you know the tree you're getting is high quality. Unfortunately, Texas has no equivalent plant material standards, meaning nursery stock can be hit or miss. ## How is Developmental Pruning Executed? Developmental pruning involves pruning young trees every 2-3 years to develop and maintain good structure. Pruning is performed more frequently in the early life of the tree, but as it matures, the frequency can be reduced. Ideally, developmental pruning should start when the tree is planted and continue until it's about 25 years old. Your arborist will begin by examining your tree for any pre-existing structural problems and determining if corrective cuts need to be made. Next, our expert crews will make targeted pruning cuts according to those specifications. Finally, we'll continue to monitor and prune your tree regularly throughout its life. With a strong foundation established through developmental pruning, your tree will be more resilient against structural stressors like strong winds and storms.

Hedge rejuvenation is like a kitchen remodel for your hedges—it's a drastic, but sometimes necessary, method of overhauling old shrubs that have become overgrown and unwieldy. This process involves reducing the size of overgrown shrubs to maintain aesthetics, improve light penetration, and promote healthy growth. As with any major corrective action taken in your landscape, it's essential to have a landscape professional plan and perform these procedures. Improper pruning can cause irreparable damage to the plant. ## Why Do We Perform Hedge Rejuvenations? Hedge rejuvenations are typically performed when hedges have become unwieldy as a result of unchecked growth. The main reasons for undertaking a hedge rejuvenation are: - To reduce the size of overgrown trees and shrubs that have outgrown their space, blocking sidewalks, windows, driveways, or other features. - To improve light penetration inside the "shell" of the hedge by removing dense branches and promoting new growth. - To restore a natural form to shrubs that have been pruned into formal geometric shapes (topiary). ## How Are Hedge Rejuvenations Performed? The hedge rejuvenation process involves several key steps. First, your arborist will identify the basic limb framework of the shrub or tree. Then, we will prune out and remove excess branches to create holes and allow more light in. A moderate amount (about one-third to one-half) of old growth is removed each year for 2–3 years, with a focus on thinning density and reducing size. Due to the drastic nature of this process, hedge rejuvenations are typically performed over the course of several years in order to maintain aesthetics while promoting healthy growth. After rejuvenation, the hedges will be stronger, more appealing, and more manageable.

Mulching involves spreading a protective layer of material, called mulch, over the soil's surface. Mulch may be either organic material, such as wood chips or leaves, or inorganic material, such as rocks. ## Benefits of Mulch Done properly, mulching is a simple and effective way to promote tree health. It has many benefits, including: - Reducing moisture loss due to evaporation - Insulating the soil against extreme heat and cold - Choking out weeds - Improving soil fertility as the organic matter in the mulch decomposes, releasing nutrients - Protecting against "mower blight"—wounds caused by mowers or weed whackers that may lead to decay - Beautifying your landscape—many homeowners prefer the tidy appearance of mulched beds ## How to Apply Mulch Winter is a great time to mulch before the extreme heat and drought of summer sets in. Apply a moderate layer of mulch, 2–4 inches thick, over as much of the root zone as possible. At minimum, the mulch layer should cover a 3–5 foot radius around, but not touching, the trunk. A 10 foot radius is ideal. If possible, use organic mulch for its beneficial impact on soil fertility as it decomposes. ## Mulching Mistakes The main goal when mulching is to cover the radius of the root zone without covering the trunk. "Mulch volcanoes," excessive piles of mulch which form a cone around the base of the trunk, are the worst example of this problem. Applying mulch against the trunk may soften the tissue and exacerbate insect and disease concerns. It may also lead to stem girdling roots which compress the stem and degrade the tree's ability to take up water and nutrients from the soil. Avoid overmulching. Layers of fine mulch that are too thick may become matted and prevent air and water from penetrating into the soil. **Avoid dyed mulch.** The chemical dyes may leach into the soil as the mulch decomposes.