When and how should I treat my spruce trees infected with adelgid?
Question:
I have three spruces (weeping, dwarf Alberta, and dwarf blue) all within a few feet from each other in a dwarf conifer section of my garden. I’ve been told by a local tree service that the damage I see on them is due to Cooley Spruce Gall Adelgid and Eastern Spruce Gall Adelgid. I’ve also been told that there is likely some White Spruce Gall Midge too. The tree service thinks that it is too late to treat the trees now and it should wait until early fall. I don’t see any insects on the spruces, only open galls that I believe are from last year. But I’m no expert. I don’t see any white waxy coatings anywhere either. I have two questions.
1. Is it too late to treat now?
2. What should I use to treat it? I typically shy away from any noxious chemicals, but I also don’t want to lose these spruces.
Answer:
After a review of several sources, it does appear that the windows for treatment are early spring and then again in the fall, with summer treatments available but less effective, so I’m inclined to defer to the tree service. Many plant pests have complicated life cycles and chemical intervention depends greatly on timing for effectiveness, otherwise you are applying product for very little return.
I will include three excellent resources for you to read through:
Colorado State Univ Extension page on Cooley Spruce Galls (this particular pest is rarely fatal to the tree, but can cause aesthetic damage)
Michigan State Univ Extension page on Eastern Spruce Gall Adelgid (this pest can reduce the tree’s vitality and overall growth if the damage is widespread)
Univ of MN Extension page on Spruce pests (includes some information on midges)
The pages provide a great deal of information on the pests, as well as treatment options for them (spring, summer, and fall).