Basic Tree Care Practices

Storm Damage, Tree Defects, and Hazards

Trees and Construction Damage

Selecting and Planting Trees

Tree Health


Frequently Asked
Questions About
Tree Health

1. What is Plant Health Care?

2. Why is my arborist recommending a Plant Health Care program?

3. The arborist said the program will be customized according to my expectations. What exactly does that mean?

4. My tree seems to be having a disease problem how do I know if it is healthy?

5. My arborist recommended a pesticide injection right into the trunk. Is that a good idea?

6. How do I rid my tree of insects?

7. Why do leaves change color in the Fall? What if my tree turns colors earlier than other trees - could this be a problem?

8. How can I help my trees survive winter?

What is Plant Health Care?

Plant Health Care, also called PHC, offers a total health approach to landscape and plant health.

How PHC Landscape Programs Work
Traditional landscape pest control programs rely on what are called “cover sprays.” The pest control sprays offered to the client are based on the company’s knowledge of common pest problems and control measures in the service area. The cover spray type, method, and timing are pre-determined by the company.The client may have the option to choose from a number of pest control programs based on the client’s priorities. Traditional pest control programs are not necessarily obsolete or “bad” for the environment and may be the best option for clients who have overriding concerns about program cost or are only concerned about one specific pest problem.

In contrast, plant health care (PHC) technicians consider the landscape as a whole when deciding how to best care for plants. PHC technicians control plant problems through careful monitoring of the landscape environment. Chemical controls may be part of the treatment but they are not necessarily used in every treatment.

The PHC technician maintains landscape plants by:

• evaluating the landscape’s environment;
• noting actual or potential causes of plant stress (stressors);
• maintaining plant performance through proper cultural practices;
• investigating the landscape through monitoring;
• and identifying and treating problems as they occur.

Because of this, every PHC program is “customized” to fit the client’s property and expectations.

Why is my arborist recommending a Plant Health Care program?
Your arborist probably recognized a potential or actual problem in your landscape that might be best avoided or treated by implementing a PHC treatment program. The following are examples of some common problems:

Many plant problems are related to improper matching of the plant’s requirements to the landscape site. This is often called “right plant / right site.” Example of this type of mistake are easy to find, the following is a common one in the eastern US. Dogwoods thrive in moist, acidic soils, especially if there is light, partial shade, but they are often planted in the middle of grass lawns in direct sunlight. Grass has different requirements than Dogwoods. Grass prefers non-acidic soils. Lawn care providers often raise the pH with lime to change the acidity level. The direct sunlight and competition with grass leads to a drier soil. The dogwood becomes stressed and more susceptible to plant diseases and insect infestations.

Plants may have been improperly planted. One common planting mistake is planting too deep. Planting too deep and other planting mistakes are often the source of plant problems.

Plants may be subjected to improper maintenance techniques. Landscapes are often subjected to improper pruning, fertilizing, irrigation, and other cultural practices. The following is one common example. Landscapes have a variety of plants with different nutrient requirements. They are often given one uniform fertilizing program that doesn’t meet their individual needs, causing stress to plants not suited to the fertilization practice.

Stress Complex. Often a combination of improper plant siting (wrong plant / wrong site), improper planting and improper maintenance techniques exist, compounding the program. These all can cause plant stress and decline, making the plant more susceptible to plant diseases, pest infestations and environmental pressures. The combined effects of different stress agents is often called a stress complex.

The arborist said the program will be customized according to my expectations. What exactly does that mean?
The whole PHC program is based on you the client and your need for a healthy, vigorous landscape.Your ExpectationsA PHC technician will consider your expectations when deciding how to implement a PHC treatment program. One important question is just when do you, the client, want to resort to chemical control of pest problems.Some clients will tolerate a greater percentage of plant damage before requiring action. Some clients will tolerate very little plant damage. Often a client will tolerate less damaged on a prized ornamental specimen tree located in the front yard as opposed to a group of shade trees growing in the back yard. This requires the PHC technician to apply a higher action threshold to some trees and/or sections of the landscape than others. Here, communication and understanding between the client and plant health care technician is key!Treatment recommendations are then made to the client based on that client’s expectations. The key to a successful plant health care program is communication between the client and PHC technician.

My tree seems to be having a disease problem. How do I know if it is healthy?

Certain trees are susceptible to certain diseases and insect problems. Sometimes what appears to be a disease is actually caused by other problems such as construction damage. Sometimes the real problem is that the tree has been weakened and/or is in decline due to a number of causes. The disease or insect is merely taking advantage of an “easy mark” since the tree has weak defenses. In this case the overall health of the tree must be addressed, otherwise infections and infestations will continue until the tree dies. See Plant Health Care.

Because of the complexity of these problems, professional help is recommended when trying to diagnose a plant health problem.

My arborist recommended a pesticide injection right into the trunk. Is that a good idea?
Injections and implants are methods of applying pesticides and nutrients to allow the material direct access into the trunk of the tree. They have been developed to control pests or diseases that have infested or infected the sapwood of a tree, to control tree pest without having to spray pesticides into the environment, or for immediate, short term treatment of nutrient deficiencies.This can be beneficial because:

• little or no pesticide is released into the environment;
• and the material is delivered directly into the vascular system where it can remain active for a longer period of time.
• Conventional spraying of tree foliage:
• offers little or no control of pests that have invaded the sapwood of a tree;
• releases pesticides directly into the environment.

Injections and implants do require holes to be drilled into the trunk, causing some wounding to the tree. This wounding should be taken into account and weighed against the possible benefits of the injection or implant.If you have concerns about drilling into the trunk, alternatives to injections and implants do exist. Soil drenches or soil injections of certain pesticides are used. They allow the pesticide to be absorbed by the plant roots and taken into the trunk without having to cause wounds in the trunk.Some trunk injections provide protection against difficult to control diseases such as Dutch Elm Disease, Oak Wilt, and Bacterial Leaf Scorch. These injections generally provide protection for a limited amount of time, such as 2-3 years, depending on the disease. They then need to be reapplied to continue the protection.

How do I rid my tree of insects?
Just as in human medicine, proper treatment begins with diagnosis. A professional arborist, nursery operator, or state/county extension agent can help you determine what the bug, or insect, is. Once the insect is identified, it can be determined if it is harmful to the tree, beneficial to the tree, or has no effect whatsoever.

Believe it or not, some insects and related critters are beneficial, because they control populations of harmful insects through predation or parasitism. It is in your best interest to keep them, so you want to avoid any treatments that take out the good bugs with the bad bugs. If the insect is indeed harmful, how harmful is it, and is it worth treating? Most professional arborists operate on the philosophy of treating only when the environmental/economic risk from the insect has reached a certain threshold.

Many bugs are benign. For instance, there is a common misconception that carpenter ants cause decline in trees! Quite the contrary, the presence of carpenter ants indicates decayed wood is present - they only make their galleries in dead, decaying sections of the tree. The ants are warning you of a potentially hazardous situation. On the other hand, termites pose a threat to trees in the southern United States and other parts of the world. They are best treated by a professional.

Why do leaves change color in the Fall? What if my tree turns colors earlier than other trees - could this be a problem?
In many parts of North America and the world, people enjoy one of nature's finest shows: Fall foliage. Leaves can be thought of as small factories containing raw materials, products and by-products, all in chemical form and some with color. As the leaf is "abandoned" by the tree, the green chlorophyll--the dominant chemical found in most leaves--is broken down and "recycled" by the tree, leaving behind other-colored chemicals. Supply lines to the leaves also become clogged. If the major chemical remaining in the abandoned leaf is red, then the leaf turns red. If it’s yellow, then the leaf turns yellow, and so on.

The yearly variation in color intensity is due to varying weather conditions, which can affect the balance of chemicals and their composition in the leaves. Differing amounts of rainfall, sunlight, temperature, humidity and other factors may have an effect on how bright, how quickly and how long the "leaf-peeping" season will be in any given year.

Pre-mature fall coloration
Color-changing leaves make for a beautiful display, but early changes in leaf-color can be a sign that your tree is stressed and is susceptible to insect and disease attack. If the leaves on your trees seem to have gotten a jump-start on fall compared with those on similar trees in the area, then you might want to consult a professional arborist, who can identify any problems and offer possible solutions. Premature colors can be an indication that a tree isn’t vigorous enough to withstand insects and disease organisms that may attack it, not to mention the usual changes that occur when the weather turns cold. Occasionally only one or two limbs of the tree will show premature fall color. This could be a sign of a disease at work, weakening only the infected limbs. The more common situation is for the entire tree to exhibit premature fall coloration, a phenomenon usually linked to root-related stress. Trees respond to these stresses by trying to curtail their above-ground growth.

How can I help my trees survive winter?
Will your trees survive the snow, ice, winter cold and winter sun? There are several short-term and long-term steps you can take to ensure your plants’ survival or lessen potential damage. Winter conditions cause more damage to trees that are stressed, so one key to preventing damage is preventing stress by keeping your trees in good health year-round.

The first protection you can offer for your trees is to site them in a good location depending on the weather in your area. Certain areas in the home landscape have different climatic conditions from their surroundings. These areas, known as microclimates, should be understood and used for planting appropriate trees. A professional nursery operator or arborist can help you choose the best tree and the ideal location to plant that tree around your house. In winter, the ground around the root system of the plant or tree freezes, stopping or slowing the circulation of water in the tree. Evergreens are at greater risk, since they hold their needles in the winter. The needles lose moisture to the atmosphere as well as to the plant itself. However, since the root system is frozen, the plant is not able to replenish the lost moisture, which makes the leaves dry out and fall off. To minimize the effects of winter drying, high-value evergreens can be treated with an anti-desiccant (usually a wax-like substance) that holds moisture in the leaves.

When the sun shines brightly on a cold winter day, it may heat up the bark of a tree to a temperature which stimulates cellular activity. As soon as the sun’s rays are blocked, the bark temperature drops quickly, rupturing and killing the active cells. This causes "sunscald," the symptoms of which are elongated, sunken, dried or cracked areas of dead bark, generally on the south side of the tree. Sunscald is most common on young, recently transplanted, tin-barked trees, so selecting a protected planting site can reduce the chance of sunscald. Sunscald of young, thin barked trees can be prevented by wrapping the trunk with a commercial tree wrap, plastic tree guard or light-colored material that reflects the sun and reduces the temperature changes in the bark.

Snow and ice can break branches and topple the entire tree. Pruning your tree can make it better able to withstand the extra weight of ice and snow. Branches can be thinned to reduce their surface area and wind resistance. Be sure to prune properly by sticking to industry-accepted pruning standards.

Some multi-stemmed trees and shrubs can be cabled together so that the extra weight of snow or ice can be shared by all the stems. It is best to hire a professional arborist for selective thinning or cabling. Mulch around the tree produces a year-round benefit because it increases the microbial activity and fertility of the soil underneath it; therefore, it is a good practice for reducing tree stress and keeping it healthy. Mulch has the added benefit of acting as insulation between the root system and the outside climate. This helps retain moisture in the root system and reduce the fluctuation of soil temperature.

Salt used for deicing streets and sidewalks is injurious to trees, shrubs and grass. You can avoid injury by using only non-injurious types of deicing salts or avoiding salt applications to sensitive soil areas. Some experts feel that you can reduce salt damage by flushing the soil in treated areas with large amount of water in the spring.