:) undefinedI need a repellant formula to deter stray dogs from pooping on my lawn.

This is a real problem, and lacks much of a good solution. One of the best things might be to pick up some of the commercial material sold at lawn and garden stores. It is meant more for flower beds, but a band around the edge of your property might help.

There was a long thread here recently on cats, but had some good ideas that might work on dogs too. Rather than try to summarize it, I will give you a link, https://www.askmehelpdesk.com/showthread.php?t=6270. Not everybody liked my ideas.

Have you thought about contacting your local animal control or if not local a county animal control to let them know there are a lot of strays so they can pick them up? That would prevent any further problems and protect innocent children from possibly being bitten by one of the strays as you never know what kind of temperament they have from running free.