You can spray all the weed killer you want, but moles eat meat. It won't change a thing.
My intent with the weed killer was not to harm the animal,,
I simply wanted them to be unhappy living where they were,, it was time for them to move away.
The groundhog ate the grass,, I would bet the 2-4D tasted horrible.

I KNOW is smells bad,,
The groundhog moved in, because it was a comfortable location.
It moved out because it was no longer a comfortable location.
Sorta like how slum lords turn off the heat to an apartment of someone that does not pay the rent.
Possibly, something like cayenne pepper spray might work.
That will keep squirrels out of bird feeders.
Birds do not even know the cayenne pepper is on the food.
BUT, the squirrels will be gone!!
It would be interesting to spray cayenne pepper spray right in the mole runs,,,
On a similar situation, we opened our pool last spring, and EVERY frog moved in,,,
There was a LOT of small tree frogs.
EVERY night there was relentless croaking,,
Well, I had heard that frogs breathe through their skin,,,,
the next night, I went out with a $2 spray bottle filled with vinegar.
I sprayed EVERY frog that I saw,,
I then sprayed the perimeter of the pool area with vinegar.
THAT ended that,, no more frog eggs,, the remainder of the summer,, PERIOD!
And the cost was a $2 spray bottle, and about $2 worth of vinegar.
The frogs must have really hated vinegar,, they moved.
There is a wet spot about 300 yards from our home,,
After our frogs were gone, we could hear frogs in that wet spot.
I do not know if ours moved there, but, our frogs were GONE!!