To make neem oil spray, combine 1-2 teaspoons of pure neem oil with one quart of warm water and a quarter teaspoon of liquid soap. Shake or stir the mix until it turns milky white with no oil floating on top. Your spray is now ready to use on your plants.
This DIY neem oil recipe costs far less than buying ready-made sprays from the garden store. One bottle of pure neem oil makes dozens of quarts of spray solution. I spend about ten cents per quart versus three dollars or more for the pre-mixed stuff on store shelves.
When I first started making neem spray, I tested different soaps to find what works best for mixing. Pure castile soap beats dish soaps with lots of added chemicals in them. The simple soap creates a cleaner emulsion and does not leave residue on your leaves. Dr. Bronners or any pure castile soap works great for this job.
Warm water helps your homemade neem oil spray blend much better than cold tap water. Heat your water to about 70-80°F (21-27°C) before you add the neem oil. Cold water makes the oil thick and hard to mix even when you add plenty of soap to help.
The soap in your mix acts as an emulsifier that bonds the oil and water together. Neem oil hates water and will not blend on its own no matter how hard you shake. Without soap, the oil just floats on top and your spray bottle shoots water with useless oily blobs.
Check your mix before you spray by looking at the color and texture. A good emulsion looks milky white throughout with no clear oil floating on the surface. If you see oil drops or streaks, add a tiny bit more soap and shake again until it blends smooth.
Use your spray within 8 hours of mixing for the strongest pest control results. The active compounds in neem break down fast once mixed with water. I make fresh batches on spray day and never save leftovers for later use since they lose most of their power overnight.
Spray your plants in the evening and coat both sides of the leaves where pests like to hide. Your goal is to see leaves glisten with moisture but not drip. Shake your sprayer every minute or so while you work since the mix can start to separate in the bottle.
Read the full article: Neem Oil for Plants: Complete Guide to Use
