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Q: I am a commercial arborist and I am interested in expanding my business to include plant heath care services. There are many techniques arborists use to apply plant health care products. Our company wants to select application techniques that are effective and profitable. Which application technique will accomplish both of these objectives?

Q&A: Expert insight regarding your tree health care questions

Q: I am a commercial arborist and I am interested in expanding my business to include plant heath care services. There are many techniques arborists use to apply plant health care products. Our company wants to select application techniques that are effective and profitable. Which application technique will accomplish both of these objectives?
— Jeff Casey, Davenport, Iowa


A: Jeff, thank you for submitting your question.

 An arborist company must have access to effective application techniques for managing their client’s tree problems. Equally important to a commercial company is having techniques that are operationally efficient and profitable.

Although there are three basic application techniques, there is a variety of equipment and many different application methods available for arborist companies to select. Before addressing your specific question it is first necessary to determine what tree care practices are defined as plant health care. Plant health care involves monitoring and using preventive and or therapeutic treatments to improve the health of your client’s trees. This may involve applications of a variety of different products like insecticides and fungicides for managing plant pests, or growth regulators, fertilizers and other products to maintain or improve tree health. Unfortunately, there is no single application technique that can be used to effectively solve all plant health care problems. Because of this, it is important to have multiple tools in your application toolbox.

To effectively control a tree pest or manage a nutrient deficiency, an arborist must be able to choose from a wide variety of products and application techniques. Once the arborist has decided which option to use he/she must determine how to best perform the work in an efficient and profitable manner.

Virtually all tree care products are applied to one of three areas: the soil near the tree or in the drip line, the trunk and limbs of the tree, or the foliage.

In general, there are three categories of application techniques commonly used for managing tree problems. These include:

Spray Application
Soil Application
Tree Injection

This article will not discuss specific active ingredients or formulations, but it is important to note that some active ingredients commonly used on trees can be applied using numerous application methods while others can be applied using only a single method. For example, the insecticide active ingredient imidacloprid is formulated in numerous products and can be applied using soil, foliar or tree injection methods.

A commercial arborist company should consider the following factors when deciding on which application technique to use:

Effectiveness of technique (does the technique predictably solve the problem)
Ease of use for applicator
Technique results in profitable returns per man hour for your business
Technique is safe for the user and environment
Ease of integrating technique into your company’s business
Technique provides flexible application timing
Technique can be used to solve multiple problems


Spray application

Spraying can be applied to the leaves or to the trunk and limbs of the tree.

Spray applications are widely used for numerous tree care applications. Foliar sprays provide the most effective way to treat leaf diseases such as apple scab, rust, and powdery mildew. Insecticides are commonly sprayed onto the trunk and limbs of trees to prevent attack by wood-boring insects such as clear-winged borers, ambrosia beetles, and pine bark beetles. In more recent years, systemic bark sprays have been applied to manage insects including emerald ash borer and diseases such as sudden oak death. Using this technique, systemic products are sprayed to the lower portion of the trunk, and move into the vascular system of the tree. The systemic products are translocated to the upper trunk and leaves.



Fast efficacy, often spray insecticide formulations are “knock-downs”
Non-invasive and do not wound the tree
Low product cost as they are diluted in large volumes of water
Small ornamental trees can be sprayed with relative ease
Application equipment can be used to apply multiple foliar spray products



Broad-spectrum products can impact non-target species
Potential for drift and applicator exposure
Difficult to obtain uniform spray coverage on large trees growing in urban areas
Short residual — applications must often be reapplied
Weather can impede operational efficiency


Soil application

Systemic products applied to the soil are among the most operationally efficient and profitable techniques available to the practitioner. Soil applications are typically done at the base of the tree using either basal drench or soil injection. Soil-applied insecticides are used to manage numerous pests on trees and shrubs. Common pests controlled include Japanese beetle, aphids, adelgids, emerald ash borer, scales, sawflies, bronze birch borer, two-lined chestnut borer and birch leaf miner. Tree growth regulators, fertilizers and soil amendments are also applied using soil application techniques.



Applications are quick (minutes/tree)
Non-invasive and do not wound the tree
Operationally predictable
More flexible treatment period, applications with some products can be made during dormancy prior to soils freezing
Equipment may be used to apply multiple products
Minimal exposure to applicators



Longer time to enter into and move throughout the tree before full protection is achieved
Most soil applied insecticides require annual applications
Soil injection requires specialized equipment
May not be viable for trees growing immediately adjacent to areas where surface water is present


Tree injection

Tree injection delivers the chemical directly into the tree’s vascular system. There are several tree injection devices and products being sold for management of tree problems. Tree injection treatments are categorized as macro-infusion or micro-infusion. Macro-infusion delivers a high volume of dilute chemical solution into the tree while micro-infusion delivers a low volume of more concentrated solution into the tree. Macro-infusion fungicide treatments are commonly used to manage vascular wilt diseases such as oak wilt and Dutch elm disease, while micro-infusions are commonly used for insect pests.



Reduces lag time between treatment and full protection
Reduces applicator exposure
Can be used in areas where other application techniques are not feasible
Provides faster results as therapeutic treatments on infested trees
Some products provide multi-year control
In some cases, the only method available to treat a problem



Longer application time. Speed of application is dependent upon favorable conditions for tree injection
Application technique is less predictable (uptake may be minutes or much longer)
Limited application window, optimal uptake occurs only during the growing season
Invasive technique that requires wounding
Specialized equipment


All of the above application methods have a role in plant health care management. Understanding the pros and cons of each will help you decide which methods will be best suited for your company’s problems and operational needs.


Shawn Bernick is director of research and technical support at Rainbow Treecare Scientific Advancements, Minnetonka, Minn. He will be answering one tree health care question in each issue of Arbor Age throughout 2010. To submit your question for consideration, please e-mail Arbor Age editor John Kmitta at jkmitta@m2media360.com. Be sure to indicate that the question is for the tree health care Q&A, and include your name and contact information.

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