Over the past few weeks many people in Cincinnati have asked when the best time is to treat their ash trees for the Emerald Ash Borer. Several mentioned that they had heard that April was best, and some said a friend told them that is was too late in the season to treat ash trees for Emerald Ash Borer.
In order to answer this question we need to be aware of two variables; the life cycle of the Emerald Ash Borer, and the type of treatment used.
The adult beetle emerges starting early May, leaving its distinctive “D” shaped exit hole 1/8th inch in diameter. Adult beetles continue to emerge through June. Eggs are laid starting mid May and continue through to August. These eggs take seven to ten days to hatch. The larvae then tunnels under the bark and starts feeding. This is the highly destructive phase of the cycle and lasts through October. The larvae pupates over winter and in early spring the adults start to emerge.
There are several treatment types. Two of the most common are soil drenching and injection.
Soil drenching: A channel is dug around the tree and filled with imidacloprid formulation. This takes four to eight weeks to be absorbed into the root system and take effect. That’s why some say April treatment is best, because the soil drenched tree will be ready for the emergence of the adults in May, and continue to kill the larvae through the fall. Because of the delay in soil drenching taking effect, treating later in the year is less effective. Also, this method need to be repeated every year.
Read about the unintended consequences of soil drenching.
Injection: The solution that Back Tree Service uses is tree injection with TREE-age. This has the advantages of taking effect within only 72 hours and remains effective for two years. Therefore injecting late in the cycle is just as effective as in the beginning of the cycle.
Therefore, the answer to the question on the best time to treat for Emerald Ash Borer is Spring though Fall with TREE-age when the leaves are on the trees. Let’s face it, if the trees are getting consumed right now, why put off treating it until next year? Once the ash borer infests an ash tree, it takes only two to three years to kill that tree. So the earlier they are treated, the less damage to the tree.
