Olio di neem

What are you trying to do/kill here? I've never found neem oil to be effective at killing off pests and especially not if it's a bad infestation... If you're dealing with anything like aphids, spidermites, thrips or whiteflies, you'll want to get some Dr. Zymes Eliminator or some Spinosad... just mix as directed and then spray the tops and bottoms of all leaves just before lights out. Both are organic and can be used throughout the whole grow, right up to the day before harvest and will kill adults, larvae and eggs of these pests... don't EVER use neem oil if your plant is in flower... If you have fungus gnats, use some Mosquito Bits - again, soak the granules as directed and then use the water for your plant (fungus gnats live in very wet soil so if you have them, you're watering your plants too much). If you have bugs that are actually chewing out chunks of your leaves, get some BT (bacillius thuringenisis) and again spray all leaves top and bottom... ALWAYS spray anything just before lights out so the leaves will not be burned under the lights... If you don't know what kind of insect you're dealing with, put up a photo of a damaged leaf and we'll be able to tell you what's causing the damage.... Good luck!