Tree
I agree that 12 inch is way to deep, I use a 6in probe.
What I am talking about here is systemic insecticide for a scale/mealybug infestation, killing a yeaw hedge. I believe this was caused by the previouse administrations fert program with out any I&D management or inspection. If you shear and fert, you need to check for critters.
TCI has a greart article on this, it put defined and reinforced my gut feelings about tree fert programs. Synopsis- N supports rapid growth, has nothing to do with photosynthate production, and dilutes th phyto chems that protect against pests.