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Photos courtesy of Rainbow Treecare Scientific Advancements be protected from EAB by soil applications, so a tree injection treatment should also be in the playbook. Now, protecting a valuable ash tree from EAB is not a one-time treatment, it is a long-term commitment that will require a treatment to be reap- plied at frequent intervals. As any tree injection requires a wounding of the tree, it is not practical that a tree could be injected on an annual basis.Tree injection formulations of imi- dacloprid were already available and had shown good data for protecting ash trees, but imidacloprid is only effective for one year. If application by tree injection was to be a part of the EAB toolbox, there would need to be treatments that were effective for longer time periods to minimize the impact of wounding each time the treatment was applied. Researchers reviewed many treatment options and discovered emmamectin benzoate could do just that; it was effective at controlling EAB, and, most impor- tantly, was shown to give acceptable control for more than one season.This now allows arborists to use tree injection treatments to effectively and responsibly protect trees when soil applications are not feasible. It’s not “what” it’s “how” The previous example of EAB treatments touches one more factor contributing to being labeled “difficult to control” and that is available application methods.There are plenty of exam- ples of tree pests where we know a certain product works, but there is a limited range of options to either get it into the tree or get it to where the pest is doing damage. Many vascular diseases can only be treated by tree injection and many foliar diseases can only be treated by spray treatments. Although they have proven management protocols, they can be significant challenges from an operations standpoint.Apple scab is not thought of a “difficult pest” but it sure is if you have high winds for a week straight and can’t get to it. New tools do become available from time to time that allow another application method option, as in the case of treatments for caterpillars and spider mites. Both these pests have had effective treatments for decades, but always needed to be applied by spraying.This is not a problem in many cases, but take a tall tree, put it in a residential area on a windy day, and sudden- ly spider mites become a tremendous management headache. Arborists now have options to control pests like these though soil applications, which can greatly reduce the number of oper- ational conflicts. Difficult, but not impossible Arborists have more options to protect trees and satisfy cus- tomers than ever before. The important thing to remember is “difficult to control” shouldn’t mean “impossible.” If you keep your tree health toolbox and protocol playbook open to new ideas, new methods, and new research, there shouldn’t be too many cases where you truly don’t have an option to meet your management objectives. Brandon Gallagher Watson is communication director at Rainbow Treecare Scientific Advancements, and is an ISA Certified Arborist (#MN-4086A). www.arborage.com • Species of the tree • Location of the tree • Size of the tree • Time of year • Severity of infestation • Environmental conditions (soil type, soil moisture, weather) Arbor Age / March 2011 23 Tree injection can be a useful tool for difficult pests but should not be done annually • No established protocol • Lack of available management tools • Poor response to management tools • Limited methods of application