No lady bug will not harm your plants, they are good for them, they eat other bugs that eat your plants. That sucks about them not wanting to eat when you buy them, i had never heard that and was going to try some, but i need them outside anyways so might toss a couple in the box to see what happens, although i am a softy even when it comes to insects.I had no pest problem until these tiny lady bugs showed up. I have only seen a few at a time but I assume they will breed. It's this going to be an issue at any point?