Asked June 02, 2023, 4:55 PM EDT
I live on a wooded lot in with many old (~100 yr) oak trees. Late last summer I saw some moderate crown die-off in one of the trees and this spring our local arborist confirmed damage from two-lined chestnut borers. While he said the tree would not definitely die, the prognosis was not great. He suggested that imidacloprid (Merit) could be used to as a potential last-resort treatment.
My question is how I should best apply the insecticide, as I feel a bit overloaded with information. Some suggest applying directly to the tree about 4.5 ft. up while the Merit label suggests a soil drench or soil injection. I have never done a soil drench before but am willing to try if it could save the tree. Do you have any tips for this? Are there any unintended consequences from using it? I am aware of its impact to pollinators and aquatic life, though we are not near water and the oaks have already flowered, so I expect minimal impact on that front.
I am also all ears if you think there is an alternate way forward.
Ramsey County Minnesota