In recent years, there has been an explosion in the population of invasive tree pests in the United States and Canada. Emerald Ash Borer, Asian Longhorned Beetle, and other insect and disease problems plague the trees in our cities and towns, threatening to change the landscape for future generations.

To combat these pests, many arborists and cities have turned to trunk injection as a successful solution. With the various methods available to the end user, trunk injection offers a flexible, environmentally-responsible alternative to soil drenches and bark sprays. The added benefits of rapid product delivery and excellent results have also helped move the technology forward. With proper training, anyone can master the art of trunk injection and save trees nationwide.

What is trunk injection?

Trunk injection of trees is a way to efficiently treat many different insect and disease problems as well as nutrient deficiencies in a manner that rapidly delivers results. This method also uses the least amount of pesticide when compared to other conventional treatment methods. Through trunk injection, small doses of insect control are carefully measured and injected directly into the tree’s transport tissues, enabling distribution within the tree, but limiting the impact to the environment.

In keeping with good Integrated Pest Management practices, stem or trunk injections typically use the least amount of tree pesticide possible with the greatest amount of control. Stem or trunk injection can be applied in environmentally sensitive areas like schools, parks, playgrounds and near waterways. Pesticide injections can be scheduled in the rain or when it’s windy. They can be done in active areas like golf courses or parks without scheduling conflicts. In addition, there is not nearly the level of cost and risk associated with heavy capital equipment. A trunk injection professional can fit all he/she needs to treat a 90-foot tree in the back of a Mini Cooper.

Why trunk injection?

Retains tree value

Trees provide shade and wind breaks which offer comfort and reduce energy costs. They retain storm water runoff to reduce city water treatment needs and they sequester carbon improving air quality. These savings have a very tangible value. Removal and replacement is also typically 10 times the cost of treatment and you don’t have the tree.

You know that trees are valuable, but just how valuable is a single tree?

• In your yard
• On your street
• At your local park
• Where you shop

One single tree can provide a value of $50-$200 each year. The National Tree Benefit Calculator is a great tool in determining how much value a tree offers a property.

Additionally, a study published in “Arborist News” in April 2009 found consumers were willing to spend 12% more in large cities for goods and services in business districts having trees.

Environmentally- responsible

Imagine protecting trees from invasive pests without worrying about off-target spray or soil applied pesticides. That’s exactly what trunk injection offers. It can be compared to a hospital shot or I.V., injecting formulations directly into the tree’s vascular system where it distributes throughout the tree.

In sensitive, high-traffic areas like neighborhoods, schools, resorts, and golf clubs, this allows the service provider the freedom to treat anytime during the day with the right dose at the right rate at the right time.

Not restricted by weather

Trunk injection can be performed any time during the growing season in nearly any weather conditions—rain, wind, and others. It’s not recommended for when the air temperature is above 90 or below 40 degrees Fahrenheit (minimum soil temperature is 40 degrees F), allowing the service provider an ample amount of time in most parts of the country to perform injections.

How does it work?

Trunk injection involves using a special injection tool which places and seals the formulation directly into the trunk where it is quickly taken up by the vascular system and distributed throughout the tree. The tree tissue associated with the vascular system of the tree is called the xylem, and it’s responsible for transporting water and nutrients from the roots to the canopy.

Injections are made in the bottom 18 inches of the tree, at intervals of around 6 inches apart. The depth for the injection is between 5/8” and 1 5/8” into the tree.

Trunk injection formulations can take hours to weeks to move throughout the tree. Most often trees are protected within a few days. The benefit of trunk injection is that the treatment is applied directly into the xylem of the tree, thus reducing the time it takes for the tree to be fully protected.

For tree injection to be successful, the applicator must possess an understanding of the basic structure of secondary xylem, its variability, and its responses to injection.  Also necessary to consider are the various formulations of injectable solutions, and how this and other factors affect application performance.  A successful injection delivers a timely and effective dose with minimal injury.

Does it injure the tree?

Trunk injection of systemic insecticides or fungicides is an effective way to manage destructive insects or diseases of trees, but many arborists are still reluctant to inject trees because of the potential for infection by pathogens, structural damage or adverse effects on tree health.

Consider this: the maple syrup you pour on your pancakes is a direct result of drilling and tapping maple trees. This practice has carried on for hundreds of years with no adverse effects for the tree. In reality, trees have adapted to repair themselves from an injury like drilling and tapping. Trees compartmentalize similar wounds without signs of infection, decay, or structural damage.

Not only is the equipment developed in such a way as to use trees’ natural responses, but the formulations are, too. Many years of scientific research in have been dedicated to creating chemical compounds that work quickly, effectively, and do not “burn” the tree. Trunk injection formulations are designed to be water-soluble to move quickly through the tree’s transport tissue.

Here’s an example: there are a large number of imidacloprid products on the market, but some were created for trunk injection and some were created for use in a landscaping spreader or other means. Imidacloprid created for spreading will not work properly if used in trunk injection and may result in severe damage to the tree. Remember, the label is the law.

How can it be used against invasive species?

Trunk injection is ideal in a number of circumstances to combat a variety of tree pests. It’s widely used in the fight against Emerald Ash Borer in the Midwest and Asian Longhorned Beetle. Additionally, trunk injection can be used to treat for Oak Wilt, Dutch Elm Disease, Anthracnose, and Chlorosis.

Most trunk injection treatments are effective for at least one growing season of protection, which means crews only have to visit a job site once each season. This limits the amount of labor costs and overhead associated with tree care, making trunk injection an economically-sound option.

What’s next?

Homeowners and general citizens alike care to keep their trees vibrant and healthy. Tree-lined streets and neighborhoods hold immense value, and protecting that landscape with trunk injection can help you grow your business. For municipalities, it can mitigate the risk of fallen trees due to insect pressure and benefit the economic wellbeing of your city.