I have a few baby Zinnia plants growing and I notice that some of them have all their leaves chewed up. I see some ugly grey coloured bugs roaming around the soil. I do spray them but I think this retards the growth of the plants.

I have just planted some more seeds and wondering what will happen. Can anyone please advise what can be done to save these lovely plants? Someone suggested spreading cornmeal so the bugs leave the plants alone.

Thanks