Just use an appropriate size net for what you want so if they are little bugs then use one where the holes arn't big enough for them to get through and if need be sit the plant pot with seedling in on top of the net and rap it around the plant pot and seedling so the bugs don't come up from the ground or where ever they come from. I'd support the net with canes so the net or what ever don't droop onto the seedling.