Neem oil might kill some plants, especially if they are young and if the oil is applied too heavily. Test a small area of the plant and wait 24 hours before applying it all over. Apply neem in the evening for outdoor plants and out of direct sunlight for indoor plants to prevent leaf burning.

How to Use Cinnamon & Neem Oil on Your Seed Starts: Damping Off Diseases & Fungus Gnats

1 tsp in 1 liter warm water. or with few drops of dish soap, which can harm small seedlings.