I'd suggest the following to try:

1. Small Green Madam-X size 14 with a midge size 20 or 22 on 7x flouro tippet trailed about 18" behind the Madam-X. The grass and the tree coverage to me just screams "terrestrial".

2. Shenk's White Minnow with a split shot about 3" above the fly. Swim it "like a bait fish" through all the water.

3. If all else fails - Olive / Black Woolly Bugger in size 12 or 14 tied about a foot behind a Hare's Ear Nymph fished in all "fishy looking" places.

These have all produced for me over the years enough that I don't even think about hatches unless I can't see the water because of the bugs in the air. #2 and #3 are just deadly searching methods for water where I can't figure out what is on the menu.