I recently had to battle some new caterpillars on my lettuce so I purchased a bottle of Bacillus Thuringiensis that needed to be diluted. Once diluted it says to use the mixture in 24 hours but it made waaaay more than I needed. I can’t dump it down the drain and I can’t use it up so what do I do with it now? Any idea how I am supposed to safely dispose?
Great answer from @Chuck
and I can't say anything further but to add that it's a common misconception that Bacillus Thuringiensis isn't safe. Well, it's a pesticide and that alone prompts the need for a safe disposal, which is kinda good coz you care for the environment.
So yeah, the Bt is totally safe and only toxic to caterpillars and critters that may be harmful to your lettuce and garden as a whole. The pesticide is actually very safe for other garden friendly insects like the ladybugs.
Also, for future preventive measures against caterpillars, I'd advise you to complement your garden with plants known to repel caterpillars e.g. peppermint, sage, lavender, and mugwort. It's their smell that keeps off the caterpillars whilst making your garden smell good.