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Author: Burkholder PHC

How Deer Repellent Keeps Your Property Safe

We all love reindeer, but when local deer begin destroying property, some deer repellent action may need to be taken. The deer population in Pennsylvania is estimated to be around 1.5 million. You have probably seen deer around your neighborhood, especially if you live in a rural or suburban area. And as much as we enjoy seeing deer in nature, the damage to your lawn and property by those same deer can be costly.

Late fall and winter is the time period that we focus on deer suppression to protect valuable plants and trees from deer damage. Burkholder PHC will outline a few ways deer can damage your yard and how particular repellent methods can help keep deer out of your garden beds and landscape.

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How Do Deer Destroy Lawns?

Deer damage lawns in two primary ways: feeding and antler-rub. These methods damage properties in different ways and may require other solutions to resolve.

Deer Feeding

Feeding is one of the more common ways deer can damage properties, and homeowners should utilize deer repellent. Deer can and will eat various plants and trees in one’s yard: grass, flowers, fruits, vegetables, and leaves; deer will even eat twigs and bark. While deer eating your plants is an obvious problem, a byproduct of their feeding is another type of damage called “browsing.” Browsing is the damage that deer cause by tearing, stomping, and compacting soil when scavenging for food.


During winter, male deer rub their antlers on trees to scrape off the velvet-like cover on their antlers to make way for a new cover in spring. The result of antler-rub is vertical scrapes and shredded bark on trees. This damage exposes the cambium, the layer that resides between the inner and outer bark. Cambium helps nutrients move throughout trees, and having this layer exposed to weather, pests, and diseases can harm your trees.

Deer in a Yard | Deer repellent | Burkholder Plant Health Care
Fawn eating grass in field | deer repellent | Burkholder Plant Health Care

How Deer Repellent Programs Can Help

To make sure that your property is safe from feeding, browsing, and antler-rub damage, some level of deer repellent may be necessary. Below are some methods we can use to prevent deer from intruding on and damaging your property.

  • To protect plants from deer feeding, agents that change their taste/texture profile can condition deer to stop eating and avoid your plants entirely. Deer have heightened senses of smell and taste, so these deer repellent sprays/agents use smells and tastes that deer generally avoid.
  • For browsing, physical barriers can prevent deer from entering certain areas of a property, like a flower bed or the boundaries of the property itself.
  • Metal or plastic trunk sleeves or wraps around trees can help stop antler-rub, especially young or newly planted trees, along with special soaps and odor deterrents to push deer to other unprotected trees.

Each of these measures also changes depending on the season. For example, the tactics for deterring deer in fall and winter may differ from spring and summer, when controlling deer behavior can be more manageable.

Burkholder PHC has a specialty program to help property owners protect their landscapes. If you are interested in our program, reach out to us today.

Contact Burkholder for Deer Repellent Services

If you need deer repellent and want to keep your property safe from deer, contact Burkholder PHC. We have experience helping homeowners protect their yards from various pests, including deer, insects, and many plant diseases. Our plant health care team is highly qualified and knowledgeable about all aspects of plant health care issues and solutions. We will work with you, inspecting your property to determine the best course of action to keep your plants healthy and beautiful. Contact us today for more information about our services and how we can help you.

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Best Time to Prune River Birch Trees

For homeowners who aspire to maintain their landscape’s health and visual appeal, knowing the right time to prune trees is helpful. Late fall to early winter marks the ideal time to prune river birch trees for several reasons, such as minimizing sap flow and preventing infestations that can lead to diseases. By adhering to this pruning schedule, you can reduce the risk of attack by pests such as birch tree borers, ensuring the longevity of your trees.

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Why Pruning Birch Trees Is Important

Pruning birch trees is essential for maintaining their health and promoting optimal growth. By selectively removing dead, diseased, or damaged branches, pruning stimulates the development of new, healthy branches and enhances the tree’s overall structure.

Regular pruning improves the tree’s health and helps prevent the spread of diseases. If one of the branches is infected, that infection can spread to the rest. So, by selectively pruning infected branches, arborists can protect the rest of the tree from further harm. In addition to removing diseased branches, pruning promotes good airflow and sunlight penetration among trees.

Accident prevention is another vital reason to prune river birch trees. Dead or weak branches can easily break and fall, especially during extreme weather conditions such as storms or snow, and these branches pose a risk to people and property. Pruning removes these potential hazards, making your surroundings safer.

Furthermore, pruning birch trees can improve the view by enhancing their natural shape and structure. Removing overgrown and crowded branches allows you to create a more visually appealing landscape.

When to Prune River Birch Trees

Knowing when to prune is just as crucial as understanding the reasons for pruning. This guide will cover essential factors, such as trimming season, birch tree age, and disease, to ensure your birch trees receive appropriate care.

river birch tree with branch cut and sap dripping - best time to prune river birch trees - Burkholder PHC

Trimming Season

As mentioned, the ideal time for trimming birch trees is late fall to early winter. Pruning birch trees during the spring should be avoided, when possible, as the spring season is when the trees produce heavy sap flows. Pruning during spring or summer can lead to excessive sap bleeding that can weaken the tree.

Birch Tree Age

The age of a river birch tree is also important when determining when and how to go about pruning or trimming the branches. Young birch trees can grow rapidly, reaching impressive heights of up to 90 feet, with their branches spreading to 60 feet.

If you want your river birch tree to achieve a desired structure, pruning needs to begin early in the tree’s life. By pruning young birch trees, arborists and plant health care experts can guide their growth and promote a healthy and aesthetically pleasing appearance.

Younger trees may require more frequent pruning to manage their growth and establish a strong structure, while older trees may only need pruning to remove dead or diseased branches.

Tree Diseases

Tree diseases can threaten the health and vitality of river birch trees. Fungal diseases can cause discoloration and spotting on the leaves. These diseases thrive in moist, humid conditions and can spread rapidly if untreated.

Bronze birch borer is an insect that can infest river birch trees, causing damage to the tree’s vascular system. Infestation by these borers can result in browning of leaves, dieback of branches, and even tree death if left untreated. Regular inspection of river birch trees will help to identify the presence of bronze birch borers and allow appropriate action.

Contact Burkholder PHC for Tree Pruning and Other Services

For expert guidance and assistance with pruning river birch trees, contact Burkholder Plant Health Care (PHC) today. Our team of horticultural and arboricultural professionals can help you maintain the health, longevity, and beauty of these magnificent trees. Reach out to us today for a free consultation.

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Burning Bush Invasive Plant

In previous articles we have been discussing invasive species and plants. One example we mentioned is burning bush. Burning bush (Euonymus alatus) is a species of flowering plant native to central and northern China, Japan, and Korea. The plant is popular in landscapes for vibrant red foliage during the fall. However, burning bush is an invasive plant species that Pennsylvania nurseries are now prohibited from selling. The shrub was first introduced in the United States around the mid-1800s, and was later deemed invasive in the 1970s.

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Burning Bush Appearance

Burning bush has a distinctive appearance with crucial aspects that can help homeowners and plant health care experts quickly identify the plant.

Size: The shrub typically grows around 15 to 20 feet tall and is often as wide or slightly wider than tall.

Leaves: The leaves have an elliptical shape, almost like a football, and are usually between 1 and 2 inches long but can be up to 3 inches long. Leaves reside on opposite sides of the branches and have smooth or finely-toothed edges or margins, which taper off at the tips.

Color: Notably, the leaves turn brilliant crimson in the fall (which is why the plant is called a “burning bush”). In the summer, the leaves are green to dark green.

Flowers: The green or green-yellow flowers have around 4-5 petals, each less than 1 inch across. Flowers begin emerging in early spring and bloom in May-June.

Fruit: Smooth, red-orange fleshy fruit appear within red capsules, which can make them blend in with the fall foliage. The berries ripen in the fall and are attractive to birds, who eat and spread the seeds.

Stems: The stems are vibrant green with distinctive raised, tan or brown corky ridges (often called “wings.”) These “wings” may follow the branch lengthwise or be whorled or twisted slightly, and their height varies.

Damage Caused by Burning Bush

While the distinctive red color appeals to homeowners, the burning bush is an invasive plant that can cause significant damage to landscapes. An important issue is that burning bush can create extremely dense thickets and complex root systems. These thickets and root systems crowd out many native plant species by taking up space, sunlight, and nutrients. This process causes the burning bush to overtake a landscape, reducing plant diversity.

What Makes Burning Bush an Invasive Plant

Burning bush has spread for numerous reasons. One of which is that due to its aesthetic appeal, homeowners were buying the plant from nurseries. However, as the damage the plant caused was more understood, the Pennsylvania Department of Agriculture designated the shrub as a noxious weed, preventing PA garden nurseries from selling the plant.

Another reason for the shrub’s spread is animals. As mentioned earlier, the fruits burning bush produces are appealing to birds, who, when eating the fruit, transport the seeds to new locations. In addition, birds pass the seeds together with other droppings, which are released into the soil, allowing new plants to grow.

In addition, burning bush has qualities similar to other invasive species that allow the shrub to spread quickly:

  • Seed Production: Burning bush produces a large number of seeds.
  • Self-Fertilization: Individual plants can contain male and female reproductive structures, allowing the plant to self-fertilize and create a whole colony of offspring.
  • Vegetative Reproduction (Sprouting): When a burning bush stem is cut or broken, the plant will grow more branches to replace the broken ones.
  • Predator Avoidance: No known natural predators feed on burning bushes, so the plant can keep growing and reproduce without any threat of predation.

Treating & Controlling Burning Bush

Plant health care specialists can use numerous control methods to mitigate or remove burning bush invasive plant populations, depending on the time of year and the conditions of the plant and landscape.

Foliar treatments occur during Mid-May to the onset of the plant’s fall color. A foliar treatment involves applying an herbicide directly to the leaves. Because the herbicide is applied to the plant leaves, this treatment option reduces the potential risk to other nearby plants because those plants do not absorb the mixture through the soil. Foliar treatment is especially good for landscapes with low to moderate plant density.

Another option is stem treatments. These steam treatments require an herbicide of a specific mixture applied to the plant. However, the mixture is applied to the stem or bark rather than the leaves in this instance.

A plant health care expert may recommend cutting or trimming the canopy for burning bush plants that are particularly large or dense. The plant can also be pulled from the ground, and the pulled plant (or cut stems) can be later chipped or burned. Cutting or trimming by itself can lead to resprouts. As a result, a plant health care expert will follow up with herbicide applications.

Contact Burkholder PHC for Invasive Plant Treatment & Removal

The burning bush invasive plant can overtake landscapes and prevent native species of plants from growing or blooming. As a result, we recommend a professional evaluation to help remove the plant and control any adverse effects. Our evaluation is free, and the proper treatments can help improve the health of your landscape plants. Contact Burkholder PHC today for a free consultation.

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Introduction to Invasive Plants

We have discussed invasive species in general as well as some invasive plants, and today we will explore invasive plants in more detail. In future articles, we will examine specific examples of invasive plants in Pennsylvania. Four plants are being phased out of nurseries and will no longer be allowed to be planted. Japanese Barberry and burning bush were phased out at the end of 2022. The other species of invasive plants in this series that Pennsylvania has added to a noxious weeds list are flowering pear trees and four species of privets.

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Introducing 4 Invasive Plant Species

Japanese Barberry is a popular ornamental plant used in landscapes across the east coast of the United States. However, as plant health care experts have become more familiar and knowledgeable, the plant has been identified as highly invasive. In addition, the shrub, known for its striking color during fall, is a host for several human diseases, including Lyme disease.

Burning bush is a flowering plant native to China, Japan, and Korea. The plant is famous for its vibrant red foliage during the fall. Burning bush is an invasive species because the plant creates extremely dense thickets and complex root systems, crowding out many native plant species.

Flowering pear trees, such as the Callery Pear, will be another banned plant species in Pennsylvania as of Feb. 10, 2024. Another species popular for its appearance, Callery Pear is similar to Burning bush because the tree proliferates and forms dense thickets, preventing other plants from growing.

Four species of privets, Chinese, European, Japanese, and border privets, can seed into the wild environments and prevent native plants needed by native wildlife and pollinators from growing.

Advantages of Native Plant Species

Native plant species offer advantages over invasive plants in a landscape. One advantage is that native plants are adapted to local soils, climates, and conditions. As a result, native plants will persist through tough climate conditions like frost and drought. Another benefit is that in their environment, native plants require less maintenance, such as water and soil amendments.

bradford pear is one example of invasive plants callery pear - Burkholder PHC

Examples of Pennsylvania Native Species

Some examples of native species of plants in Pennsylvania are as follows:

  • Trees: Eastern Redbud, Dogwood, and Red Maple
  • Shrubs: Azaleas, New Jersey Tea, and Smooth hydrangea
  • Perennials: Virginia bluebells, Black-eyed Susan, and Butterfly milkweed

Next month we will discuss the Japanese Barberry in more detail: what the plant looks like, what makes the species invasive, the potential for harm, and control methods and solutions.

Contact Burkholder PHC for Invasive Plant Treatment & Removal

If you are concerned about invasive plants in your landscape or want more information because these plants are affecting your property, contact Burkholder PHC. We provide a free evaluation by our highly experienced, qualified plant health care experts to help remove and control invasive plants and control any adverse effects. Contact Burkholder PHC today for a free consultation.

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Protect Your Plants from Powdery Mildew

As a plant health care company, our responsibility is to bring urgent matters concerning the health of your plants to your attention. One potential threat to your thriving landscapes comes from a plant pathogen known as Powdery Mildew. This plant disease compromises your plants’ vitality by attacking the leaf surface. Today, we provide information about their identifying characteristics and the strategies that can be employed for effective disease management, ensuring the health of your plants.

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Understanding Powdery Mildew

Powdery mildew predominantly affects the leaf surface of plants, reducing their beauty and vitality. Various species can cause this fungal disease. Their strength lies in their numbers, with a deluge of microscopic spores – known as conidia – attacking plants. As the fungal disease spreads over the plant surface, intricate structures develop that penetrate plant cells, siphoning nutrients to fuel fungal growth.

Symptoms & Damage

Powdery mildews display the following symptoms on an infected plant:

  • White, powdery growth on leaves’ upper and lower surfaces.
  • The powdery growth may be challenging to see initially, but will become more pronounced as the infection progresses. 
  • Leaves may become yellow, curled, and distorted.
  • Flower numbers are reduced.
  • Plant growth slows down or stops altogether.

Powdery mildew can spread to other parts of the plant, eventually leading to death if untreated. The unchecked spread of this disease can lead to ramifications such as stunted growth, premature leaf fall, and reduced yields and fruit quality.

Life Cycle of Powdery Mildew

crape myrtle plant with powdery mildew on leaves - Burkholder PHC

    Powdery mildew is encouraged in warm (60-80°F) and dry conditions. Different humidity conditions affect powdery mildew spores and their behavior:

    • High humidity encourages spore formation
    • Low humidity encourages spore dispersal

    Powdery mildew does not spread in cooler, rainy conditions and is slowed by high temperatures (>90°F). New spores are produced every 3-14 days once germinated.

    The process of germinating and spreading spores is important to understand, too. The beginning stages involve fungal spores landing on a new host plant, germinating, and reaching the leaves. From here, the hyphae produce the conidia: tiny, asexual spores in chains. These conidia are dispersed by wind, water, insects, or people touching the infected plants.

    Powdery mildew infections are most severe in crowded, shady, and poorly ventilated areas. A powdery mildew fungus affects plants more in shady than sunny areas In addition, free water is not required for germination and infection, but high relative humidity is required around the plant for the fungus to spread.

    Vulnerable Plant Species

    While powdery mildew can affect hundreds of plant species, some plant species are more vulnerable to these diseases than others.

    Some common plants that are vulnerable to powdery mildew include:

    • Azalea
    • Crabapple
    • Crape myrtle (pictured right)
    • Dahlia
    • Dogwood
    • English ivy
    • Euonymus
    • Lilac
    • Oak
    • Pecan
    • Phlox
    • Photinia
    • Pyracantha
    • Rhododendron
    • Rose
    • Spirea
    • Snapdragon
    • Wisteria
    • Zinnia

    crape myrtle plant with crape myrtle - Burkholder PHC

    Effective Management and Control

    The best treatment for powdery mildew is prevention, because the condition is difficult to eliminate. The best treatment option for you will depend on the severity of the infection, the type of plant, and the climate.


    A few fungicides are available, both organic and synthetic, but they can have negative impacts on other plants or environments, so professional application is recommended. For example neem oil kills insects, including bees, so must be handled carefully. Copper or phosphorous are examples of organic fungicides that are often used as preventive measures with repeated applications during the season when the conditions are ripe for germination and spread.


    Selective pruning of plants and plant debris can help maintain proper air circulation between them, which keeps humidity low to prevent diseases from spreading.

    Soil Care

    Soil that is overwatered or poorly drained helps create conditions for the disease, so proper drainage and irrigation is used as a preventive method.


    In severe cases where other options are ineffective, removing the plant may be necessary to protect other plants from becoming infected.

    Contact Burkholder PHC for Plant Disease Mitigation

    To keep your plants vibrant and safe from powdery mildew, contact Burkholder PHC for more information or to schedule a consultation. We have a team of experienced, qualified experts that can help homeowners maintain the health and appearance of their plant life. With years of experience in plant disease control and integrated pest management, our team knows how to treat plant health care issues so you can keep your landscape beautiful.

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    Introduction to Fall Webworm

    Some insects challenge the health and longevity of our cherished landscape plants and one such pest is the Fall Webworm (Hyphantria cunea). This moth is native to North America and causes significant defoliation and stress to around 90 deciduous tree species, including birch, hickory and walnut. Today we will discuss the physical characteristics, complex life cycle, damage caused by, and management of this insect.

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    Fall Webworm Appearance

      The physical appearance and characteristics of the fall webworm change as it goes through its life cycle.

      Egg Masses

      The egg masses are tiny and covered in white hairs, giving off an almost cottony appearance. The masses can contain hundreds of these eggs, which are light yellow in color.


      Upon the initial stages of hatching, the larvae are a pale, almost bleary yellow with two distinct rows of black marks adorning their bodies. As these larvae mature, they display a variation of colors and patterns.

      Once full-grown, the larval bodies are covered with fine, whitish hairs originating from distinct black and orange warts.

      The coloring of these larvae varies, most often greenish sporting a broad, dusky stripe running along the back and a yellow stripe on their sides.

      Pupal and Adult Stages

      As the larvae move into pupation, they adopt a brownish color. Adults can vary considerably in their coloration. Some may remain pure white; others appear white with black spots. Adult moths have a wingspread of about 32 mm.

      The Lifecycle of the Fall Webworm: A Journey from Pupa to Pest

      The lifecycle of a fall webworm begins as a pupa—a hibernating life stage that they assume during winter. During this stage, the pupae envelop themselves in a cocoon while concealed under ground litter, within cracks and crevices of trees, or in the soil.

      Fall webworm larvae on a black cherry tree branch - Burkholder PHC
      Fall webworm on a black cherry tree- Burkholder PHC

      Emergence and Egg Laying

      As winter recedes, adults emerge from their cocoons in early summer, around mid-June. Adults continue to appear intermittently in small numbers through the summer months. Females begin depositing their eggs on the undersurface of leaves.

      From Hatchlings to Larvae

      The hatching commences approximately seven days after the eggs have been laid. As soon as these larvae hatch, they spin small silken webs or nests over the foliage that is their food source. As they get larger, they expand their area, spinning increasingly large nests to enclose more foliage, and they can eventually grow to a 3-foot span. The remains of these webs can often persist till winter. Larvae sharing their foods and homes with other larvae until their last molt, when they may adopt independent feeding habits.


      The maturation process of these larvae only takes roughly six weeks. Once mature, these full-grown larvae vacate their webs and pupate in or on the soil—slipping again into dormancy as the temperature decreases.

      In our geographic location of Main Line, PA, there’s typically a single generation each year. However, a second generation might occur in certain years and under particular conditions.

      Damage Caused by Fall Webworm

      During the larval stage, fall webworm consumes leaves inside the protection of their webs, leaving skeletonized leaves. Skeletonization is when only the leaf’s veins, or “skeleton,” remain intact, with the surrounding tissue removed. This prevents photosynthesis and can ultimately lead to the death of a plant.

      As the fall webworms grow, they require additional food and will feed on more plants. 

      While fall webworms may defoliate a tree occasionally and reduce the ornamental value, the pests will rarely kill the tree.

      Management of Fall Webworm

      Protecting the well-being of your landscape from fall webworms can happen in various ways. Some methods may be better suited to one landscape compared to another. We will explore the management strategies that can help protect your garden from unnecessary harm.

      Removing Webs Early

      Due to their extensive webbing, the nests tend to be visible on the tree canopy. Whenever you spot a nest, mainly while the nest is still small and easily reachable, a plant health care expert can prune them out and dispose of them. Remember that early detection and removal can help you significantly reduce the size of the webworm population.

      Biological Controls

      Some biological predators and parasitoids naturally keep specific insect populations in check by feeding on fully-grown pests or even egg masses. Birds, beneficial insects, and certain types of fungi and bacteria all feast on webworms, curtailing their potential to harm your plants.


      As a last resort, the careful use of insecticides may be warranted when heavy infestations threaten significant foliage loss. Applying an insecticide, particularly one containing Bacillus thuringiensis or Spinosad, can disrupt the life cycle of fall webworms. Employing these should be a calculated decision because of their non-selective nature, so as a result, a plant health care expert should be involved to ensure any insecticides are applied correctly and their effects on non-infested plants minimized.

      Integrated Pest Management (IPM)

      Integrated Pest Management (IPM) is a comprehensive and coordinated approach that combines a variety of tactics for long-term management of pests. This approach aims to minimize risks to people and the environment. IPM includes techniques such as biological control, habitat manipulation, modification of cultural practices, and use of resistant varieties.

      Contact Burkholder PHC for Pest Management Services

      Some species of insects, like fall webworms, have the potential to harm people’s landscapes. Burkholder PHC has years of experience helping homeowners in the Main Line region care for plants and manage insects. Our specialists will survey your property, evaluate your plants, diagnose the issues, and inform you of the recommended treatment options. Contact us today for a free consultation.

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      The Importance of Corrective Pruning and Structural Pruning

      As plant health care experts and certified arborists, we provide homeowners with knowledgeable expert care services for their plants and trees. One aspect of our work requires a clear understanding of pruning practices: corrective pruning and structural pruning. Pruning is a crucial aspect of plant health care because it helps to control plants’ growth and maintain their structure, health, and appearance.

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      Corrective Pruning

      Corrective pruning is the removal of broken, diseased, dead, or other unsafe branches from a plant. Some of the benefits of corrective pruning are:

      • Increased airflow and light penetration: Pruning selected branches can help allow more sunlight to reach a shrub or tree and ensure better airflow, leading to the improvement of the overall health of the plants.
      • Return tree to natural form: Corrective pruning helps restore the plant to a natural shape.
      • Permits groundcover: The pruning process opens up the landscape, allowing groundcover plants to flourish.

      For example, we performed corrective pruning on this juniper shrub. You see the from the shrub’s appearance before and after the shrub was taken back to more of a natural, less dense form, which will allow better airflow and less competition for nutrients.

      • Juniper shrub before corrective pruning - corrective pruning and structural pruning -  Burkholder PHC

        Juniper shrub before corrective pruning

      • Juniper shrub after corrective pruning - corrective pruning and structural pruning - Burkholder PHC

        Juniper shrub after corrective pruning

      Structural Pruning

      On the other hand, structural pruning involves trimming young and developing shrubs or trees to promote a strong and healthy structure. Structural pruning’s benefits include:

      • Reduced potential for storm damage: A well-structured tree or shrub is less likely to suffer severe damage in a storm. For example, broken or weak branches are more likely to fall off during strong winds and could damage property or residents.
      • Reduced disease issues: Proper structural pruning can remove diseased parts of trees, thereby reducing the spread of disease or pests.
      • Reduced future maintenance costs: Regular structural pruning can save homeowners from high-cost emergency tree work by making their trees safer early on.

      An example of structural pruning is our recent work on cherry laurel shrubs. Our team reduced these cherry laurels to gain visibility to this client’s window boxes. Hand pruning is the best way to reduce cherry laurels so we can make all internodal cuts (cuts made between buds or lateral branches.) The shearing of cherry laurels will often cause the browning of severed leaves.

      • cherry laurels in front of a house - before structural pruning - Burkholder PHC

        cherry laurel before structural pruning

      • cherry laurels in front of a house - after structural pruning - Burkholder PHC

        cherry laurel before structural pruning

      Best Times for Corrective & Structural Pruning

      The best time to perform corrective pruning and structural pruning is during the dormant season, typically in late winter or early spring for most plants. Shrubs and trees are not actively growing during this time, therefore plants do not expend energy on growth, so any wounds from pruning will heal more quickly and easily.

      Here are some specific reasons why the dormant season is the best time to prune:

      • Less Chance of Disease: In warm summer months when pests are more active, tree wounds are more prone to disease or infestation. During the cooler dormant season, trees and shrubs have less risk of infection.
      • The tree is less stressed: A tree is more stressed when actively growing. Pruning during this time can add to the stress, making the tree more susceptible to disease and pests. During the dormant season, the tree has more energy to devote to healing the pruning cuts.
      • Seeing the branch structure is easier: When trees and shrubs fully bloom in spring or summer, identifying which branches we need to prune can be more challenging. When a tree is dormant, and the leaves have fallen off during winter, we can see the branch structure more clearly and easily identify which branches we need to prune or trim.

      Contact Burkholder PHC for Corrective & Structural Pruning Services

      If you need help with corrective pruning and structural pruning, contact us at Burkholder PHC. Our team of experienced, qualified arborists will visit your property, evaluate your landscape and plant health, diagnose the problems, and inform you of the recommended treatment options. We provide a proactive approach, identifying and resolving plant health problems before those issues impact your landscape. Contact us today for a free consultation.

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      The Hemlock Woolly Adelgid: Spotlight on an Invasive Species of Pennsylvania

      In the fourth installment of our series on invasive species of insects, we will discuss the hemlock woolly adelgid. The hemlock woolly adelgid (HWA, or adelges tsugae) is a tiny, sap-sucking insect native to East Asia. Recognized as an invasive species in the United States, the pest has been identified in multiple states and was found in Pennsylvania in the late 1960s. The HWA is a significant threat to eastern hemlock trees, the state tree of Pennsylvania.

      As plant health care professionals, we want to help you and other Pennsylvania residents understand the impact of this invasive pest and keep your hemlock trees safe. Below, we discuss the characteristics, life cycle, damage and treatment of hemlock woolly adelgid in Pennsylvania.

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      Identifying the Hemlock Woolly Adelgid

      Adelgids are a small family of insects closely related to aphids that feed on the plant sap of conifer trees and, in the hemlock woolly adelgid’s case, hemlock and spruce trees. The insect measures less than 1/16 inch (1.5mm) and is covered in a wool-like wax filament, giving the pest a “cottony” appearance. Females are black, oval, soft-bodied, and about 1.5 mm long. HWA is primarily found on the underside of hemlocks’ branches, nestled against the base of the needles.

      The Life Cycle of the HWA

      The hemlock woolly adelgid possesses an intricate two-year life cycle, encompassing four immature stages and culminating in a reproductive adult phase. Throughout late winter and early spring, as temperatures climb, adult female HWAs begin laying eggs. These clusters of eggs, housed within white filamentous wax masses, continue to be laid until June. Measuring 0.25 mm in length and 0.15 mm in width, the oblong eggs have a brownish-orange color. Depending on the warmth of the spring season, hatching starts in early April and typically concludes by the end of June.

      Emerging as reddish-brown nymphs, or “crawlers,” these young insects display a delicate white fringe near their anterior. Once settled, crawlers grow to approximately 0.3 mm long, and take on a black hue with a white fringe that encircles their bodies and extends along their dorsal side. As these nymphs develop, their color deepens to a dark reddish-brown, and their size progressively increases due to active feeding habits. By late September, these mature female insects reside on trees, overwintering before repeating the reproductive process of the species.

      Hemlock wooly adelgid on a branch - Burkholder PHC
      Dieback on hemlock from hemlock wooly adelgid-burkholderphc

      Recognizing an Infestation

      The most apparent sign of HWA infestation is the white, “cottony” egg sacs on the underside of hemlock branches that the females produce when laying eggs. These egg sacs look much like the tip of a cotton swab and typically persist even after the insects are dead. Other signs include needle loss, reduced twig growth, and dieback of branches.

      Damage Caused by Hemlock Woolly Adelgid

      The impact of an HWA infestation on eastern hemlock trees can be catastrophic to the tree, depending on the extent of the infestation. The adelgids use sharp, syringe-like mouthparts, or stylets, to siphon off essential plant fluids from host plants. This feeding activity takes a toll on the plant’s overall health.

      A moderate population of the hemlock woolly adelgid may lead to a noticeable decline in the health and vigor of your trees. However, the consequences become more serious in a severe infestation. This could result in a premature shedding of needles, diminished growth of twigs, significant dieback, and in worst cases, the loss of the tree. This danger to the trees makes early detection and decisive action in managing these unwelcome pests important.

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      Managing & Controlling Hemlock Woolly Adelgid

      We are often asked to manage this pest in late September through October. We use several methods for managing infestations of hemlock woolly adelgid.


      Registered systemic insecticides applied in late September and October can reduce hemlock woolly adelgid populations and temporarily prevent the establishment of new infestations for up to seven years. These systemic insecticides are usually injected into tree trunks or applied as a soil drench or injection. These insecticides often target overwintering females.

      A plant health care expert can also apply sprays during other times of the year. A mid-to-late June spray may help reduce the number of developing nymphs. This management strategy is appropriate when thorough coverage is difficult to achieve using ground application equipment. Early spring soil injections usually work well against this pest when the soil is sufficiently irrigated.

      Biological Control

      Predatory insects can also be used to control HWA populations. The species most commonly used for this application are Laricobius nigrinus, a beetle native to the western United States, and Sasajiscymnus tsugae, a beetle native to Japan. Both beetle species are attracted to the white woolly egg masses that HWA produces. In addition, the beetles feed on the HWA, and their larvae also feed on the pest.

      While most often used in forests, this method is becoming more common for residential hemlock trees in the United States. This is because biological controls to remove species of harmful pests can be a more environmentally friendly method of control than using chemicals. As with insecticides, a qualified arborist should perform this treatment. A certified arborist can help you assess the severity of the infestation and recommend the best course of action.

      Contact Burkholder PHC for Hemlock Woolly Adelgid Treatment in Your Landscape

      If you suspect or are concerned about the presence of hemlock woolly adelgid on your property, contact Burkholder PHC for expert advice and treatment options. We provide a free evaluation by our highly experienced, qualified plant health care experts and certified arborists to help remove and control invasive species and the adverse effects these pests cause. Contact Burkholder PHC today for a free consultation.

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      Emerald Ash Borer: A Threat to Pennsylvania’s Ash Trees

      In this third installment of our series on invasive species of insects, we will discuss the emerald ash borer (EAB). This invasive woodboring beetle has wreaked havoc on ash tree populations in Pennsylvania and other states in the United States and other regions in North America. As a homeowner, you should understand the impact of this invasive pest. Below, we discuss the characteristics, life cycle, and damage caused by emerald ash borer in Pennsylvania as well as some prevention and treatment methods.

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      What Is the Emerald Ash Borer?

      The emerald ash borer (Agrilus planipennis) is a small, metallic green species of beetle native to northeastern Asia that has become invasive to North America. The beetle was first discovered in the United States in 2002 in Michigan and has since spread to 30 states, including Pennsylvania. EAB attacks and kills ash trees in North America by feeding on their inner bark, disrupting the tree’s ability to transport water and nutrients.

      Emerald Ash Borer Appearance

        Adult EAB are distinguished by their bright metallic green color and are approximately 1/3 of an inch (8.5 mm) long and about 1/16 of an inch (1.6 mm) wide. Females are also slightly larger than males. The elytra (hard shells that serve as protective cases for wings) are typically a darker green but can also have copper hues. Another distinguishing feature of the adult emerald ash borer species is its bright red upper abdomen that can be seen when the wings and elytra spread.

        emerald ash borer on a leaf - photo by Brian Wheeler, United States Department of Agriculture

          Larvae are white to cream-colored with 10 abdominal segments. The last segment has a pair of brown, pincer-like appendages. Larvae typically reach a length of 1 to 1¼ inches.

          tree damaged by emerald ash borer-Burkholder PHC

          Emerald Ash Borer Life Cycle

          The emerald ash borer has a 1-year life cycle. Adult beetles emerge through D-shaped exit holes in a tree around late May and early June—adult activity peaks between mid-June and early July. After appearing, the adult beetles feed on ash foliage for several days and then begin to mate. Females lay approximately 60-90 eggs in their lifespan, which hatch in 7 to 10 days.

          After hatching, the larvae tunnel through the bark into the ash tree’s phloem (plant tissue). Larvae feed on phloem for several weeks, creating S-shaped paths in the tree under the bark. As larvae grow, these galleries become progressively wider. Prepupal larvae overwinter in shallow chambers within the bark. Pupation begins in late April or early May and lasts 1 to 2 weeks when this species’ life cycle starts again.

          Signs and Symptoms

          If you have ash trees on your property, knowing the signs and symptoms of EAB infestation is crucial to keeping them safe and preventing damage. These signs include the following:

          • Thinning canopy and dieback of branches
          • D-shaped exit holes in the ash tree bark
          • S-shaped galleries under the bark
          • Increased woodpecker activity (as woodpeckers feed on larvae)

          Damage from Emerald Ash Borer

          As mentioned above, EAB larvae feed on the nutrient-rich inner phloem, cambium, and outer xylem beneath the bark, creating S-shaped galleries packed with sawdust-like frass. As the infestation of this invasive species progresses, the symptoms mentioned above become more apparent. Trees will die after 3 to 4 years of heavy infestation, making EAB control tactics crucial to preserving ash tree populations.

          Preventing Emerald Ash Borer Infestation

          Prevention is the best way to avoid damage, and there are several steps you can take to protect your ash trees from EAB:

          • Do not move firewood: Moving firewood can inadvertently transport EAB to new locations. Some states, including Pennsylvania, have restrictions on moving firewood because of invasive insect species. Always buy firewood locally and burn on-site.
          • Use insecticides: Preventive insecticides containing certain ingredients and agents can be applied to healthy ash trees to protect them from EAB. Consult a certified arborist for advice on the appropriate insecticides and application methods.
          • Plant diverse tree species: Planting a variety of tree species can help reduce the impact of EAB on your property and promote a healthier ecosystem.

          canopy dieback from emerald ash borer infestation-Burkholder PHC
          tree being treated for emerald ash borer infestation - Burkholder PHC

          Damage from Emerald Ash Borer

          As mentioned above, EAB larvae feed on the nutrient-rich inner phloem, cambium, and outer xylem beneath the bark, creating S-shaped galleries packed with sawdust-like frass. As the infestation of this invasive species progresses, the symptoms mentioned above become more apparent. Trees will die after 3 to 4 years of heavy infestation, making EAB control tactics crucial to preserving ash tree populations.

          Treating EAB Infestation

          If your ash trees are already infested with EAB, Burkholder PHC offers various treatment options, including:

          • Insecticide: Treatments can be applied to infested trees to kill EAB larvae and prevent further damage. Some application options include soil drenches, soil injections, or stem injections.
          • Tree Removal: In some cases, infested trees may need to be removed to prevent the spread of EAB to nearby healthy trees.
          • Replacement Planting: After removing infested trees, consider planting a diverse selection of tree species to help restore the ecosystem.

          Contact Burkholder PHC for Emerald Ash Borer Treatment in Your Landscape

          If you suspect or are concerned about emerald ash borer impacting your property, contact Burkholder PHC for expert advice and treatment options. We provide a free evaluation by our highly experienced, qualified plant health care experts and certified arborists to help remove and control invasive species and the adverse effects these pests cause. Contact Burkholder PHC today for a free consultation or more emerald ash borer information.

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