Tree aphids – black in color
The tree [15-18 ft tall] is in my dogs pin and is heavily infested with black aphids. I have neem oil and want to use it as a systemic because of my dogs. What is the ratio to use neem oil as a systemic solution?
Neem oil is not a systemic insecticide. There is one water soluble neem Azadirachtin product (Azasol) that can be soil drenched for root uptake, or professionally injected into the stem for vascular system uptake. But neem is not the best choice for an active infestation. It's best for prevention or early intervention.
Consider this: mid to late September in central Kentucky, those aphids aren't going to be there for long. And a systemic won't move and translocate within the tree tissues once the temps drop and metabolism slows down.
You didn't say what kind of tree, but big black aphids, I'm thinking "giant conifer aphids". If it's a birch, the leaves and the aphids will be down and out real soon.
If an evergreen, you could have a professional with a hydraulic sprayer and a deep root injection needle, do a subsurface soil application with Merit 2F (imidacloprid) or equivalent. That will be a slow uptake and not control anything this year, but it will be effective all next year. You could also do this treatment in early spring when new growth starts. Just take the dogs out of the run during application and follow up with a deep watering.
If that is not an option, and you are intent on controlling the aphids now, or wait until you see them next summer, - an organic program compatible knock down insecticide is pyrethrum (not to be confused with the sythetic chemical pyrethroids or permethrin):
https://www.domyown.com/evergreen-pyrethrum-concentrate-p-1875.html This botanical contact spray biodegrades with sunlight in 12 hours, after which you and the dogs can re-enter.