Neem oil is wonderful to use in the garden as a natural insecticide that is safe for beneficial bugs, as well as having anti-fungal properties which prevent mildew and other fungal diseases on plants. Neem oil works against chewing and sucking insects like aphids, whiteflies, and mealybugs, without harming bees and other pollinators.
Neem as a general preventative:
1/2 tsp neem oil
1/4 tsp Dr. Bronner's Castille Soap
2 cups warm water
For a stronger batch, with more severe pest problems, increase the amount of neem oil:
1 tsp neem oil
1/4 tsp Dr. Bronner's Castille Soap
2 cups warm water
It is best to make this in small batches because it loses its effectiveness over time when the ingredients are mixed together. I usually make a single use spray each time since I think that way the neem keeps its top effectiveness (the beneficial properties in neem oil begin to break down 2-3 hours after mixing).
Single use spray:
1/4 tsp. neem oil (15- 18 drops)
1/8 tsp. castile soap (my measuring spoon doesn’t go that small, so I just estimate)
4 oz. warm water
Neem begins to turn to a solid at room temperature, so if you open your bottle and see clumps of oil, run the bottle under warm water for a minute before using.
Mix all the ingredients in a spray bottle and shake well before use. Spray liberally on affected plant foliage.
Neem oil is only bad for bugs that chew on leaves (because of this, I would not use it on host plants for butterflies like milkweed).
The neem oil spray should be used early in the morning or in the evening since it's best not to spray plants when the sun is at its strongest. Morning and evening are also when pollinators are less active. This neem spray will not harm beneficial insects unless they are directly sprayed.
Spray every few days for intensive insect problems, once every two or three weeks for prevention. I was having a really bad time with some sort of insect sucking and curling the new leaves on my phlox plants, so I sprayed those plants every day for a few days and now the new leaves seem to be growing in healthy without any curling.
Neem is safe to use on vegetable plants, but it's best to discontinue its use five weeks before harvest.
