I opened a bottle of Gourmet Liquid Ant Bait purchased last year and noticed there was a small layer of what looks like dark mold on top of the bottle. The rest of the liquid looks normal. Do you think it's still effective? If not, how do I dispose of it?
If it has mold it is probably no good. I would simply pour it out next to your foundation and then cover it with some dirt or mulch. Whatever insects eat it at the at point will die, so you are getting some benefit.
Gourmet Liquid Ant Bait should last about 6 months in an unopened bottle. There are no added ingredients to prolong the life so it has a limited life span.