Agriphos will not work to control any foliar fungi. JD gave some good fungicide options. The timing you want to hit is before bud break, during bud swell, after bud break during leaf expansion. You man need to do more fungicide treatments then that depending on your area, but here in the PNW 3...
Bark character alone does not make for a good ID.
What helps is: 1- overall canopy shape 2- close up of twig and bud arrangement 3- any fruit flowers or leaves.
So you are saying you have a one dead branch to remove from your willow oak? prune just outside of the branch collar, dont cut into live wood. Otherwise, call a certified arborist to help with how when and what to prune.
What photo are you looking at Mr. Tree? the photo I put up did not have leaves or fruit pictured. This tree was at the Hoyt Arboretum, in the mountain ash collection. with a tag on it. and it looks like other whitebeams i've seen.
I think you are looking at the previous tree I posted, the...