Yeah, I'd wait until they have a few nodes and stand up strong. Always spray really well under the leaves, and the soil surface, each time you use it. Plain old cold pressed neem oil is one of the best IPM choices out there-if you use it once per week up until flowers start forming, you shouldn't have any trouble with insects or fungus. One thing to consider getting is the small bottle of Southern Ag Garden Friendly Fungicide. I add a few drops in with the neem mixture, and I also spray it separately and add it to my nutrient solution once per week as a root drench, it's only $7.99 for the small bottle. It's extra insurance against PM and botrytis during flowering, and it also prevents damping off in seedlings. You can start using it from seed/cutting.