Robyn,

If you were me, would you place a dwarf sweet-cherry tree 30' away from your pond, which contained lilies - subject to aphid infestation. In my case, the tree is 5' downhill.

We have acres full of trees and lots of wild black cherry trees all around us. We also have lots of aphids! So for me, I wouldn't even worry about it. That one tree that you want to plant is just one in a sea of millions. It wouldn't noticeably increase your aphid population unless you have no trees around at all. I've got aphids in my plants inside in the basement (and have had no time to move them outside yet) too. Being that the tree you want is a dwarf means it's even less of a factor. Enjoy those cherries! I wish some of our fruit trees would produce fruit!

i only have mapple trees - and not too close to the pond

i thought that cherry trees cause a lot more aphids then many other trees

is there a benefit to having a cherry tree near a frog pond - will it attract a lot of bugs for frog food - i dont think much fruit remains/drops to the ground

Yes, I've read that aphids may overwinter on cherry trees. As I said, I have so many trees that I don't even think about it. Cherry trees will attract pollinating insects in the spring for a few weeks but a bee in the mouth may not be great for a frog. The frogs won't eat the fallen fruit but any such fruit would attract ants, fruit flies, etc. which the frogs might eat. I don't think a single dwarf cherry tree will make much difference in the aphid population or food supply for the frogs.

it has always been my understanding that frogs and toads eat bees and wasps - i dont remember if ive seen this, but may test it out

i wonder if they are, or even iz, immune

Yes, they'll try to eat them. But, the insects will sting. I don't know if the venom harms the frogs per se (if it does, it would paralyze them) but it's not fun to have a hole popped in your mouth either by a nasty stinger! In many cases, the frog probably crunches the bees/wasps/hornets before being stung but not always. I would suspect that if a frog is stung, it learns to avoid those bugs.