As the Emerald Ash Borer (EAB) continues its march across the United States, many homeowners, tree care professionals, municipalities or arborists often wonder if there are options to treat their trees to protect them from this invasive insect. Since 2002, scientists have learned much about EAB and methods to protect trees with the use of insecticides.
Keep in mind, however, that controlling insects that feed under the bark with insecticides has always been difficult. This is especially true with EAB, because our native North American ash trees have little natural resistance to this pest. In university trials, some insecticide treatments were effective in some sites, but the same treatments failed in other sites. Furthermore, in some studies conducted over multiple years, EAB densities continued to increase in individual trees despite annual treatment. Some arborists have combined treatments to increase the odds of success (e.g. combining a cover spray with a systemic treatment).
Our understanding of how EAB can be managed successfully with insecticides has increased substantially in recent years. However, it’s important to note research on management of EAB remains a work in progress. Scientists from universities, government agencies and companies continue to conduct intensive studies to understand how and when insecticide treatments will be most effective.