Neem oil is an extremely useful “natural insecticide” coming from the nuts of the Neem tree.
The oil contains a naturally pesticidal compound called Azadirachtin, which is extremely useful for combating a wide variety of plant insect pests such as:
- Fungus Gnats Larvae
- Japanese beetles
- Moth Larvae
- Mealybugs – read Does Neem Oil Kill Mealybugs?
- Spider Mites
- Aphids (Plant Lice) – read Neem Oil For Aphids Feeding On Plants
- Plant Scale
When plant pests consume Azadirachtin, Neem kills these bugs gradually by acting as a growth inhibitor and an appetite suppressor.
This twofold action causes both failure to molt and starvation.
This natural substance is effective against above-ground pests when sprayed on plants.
It is effective against belowground pests when used as a soil drench.
Even though Neem oil is fairly benign to beneficial insects when you choose to use it as a soil drench, you eliminate any chance you might accidentally harm bees, predatory insects, and other good bugs.
Related: Does Neem Oil Hurt Bees?
How Does Neem Oil Soil Drench Work?
A Neem soil drench works as a systemic insecticide even on fruit trees.
This means the plant absorbs the effective ingredient in the drench (e.g.Azadirachtin), which is distributed throughout the vascular system of the plant. [source]
When this happens, any part of the plant ingested by a pest contains the pesticidal ingredient.
As a bonus, Azadirachtin also helps protect plants against fungal infections when used in this manner.
This means using Neem oil root drench can help defend your plants from soil-dwelling larvae and problems such as root rot. Check out these tips on using Neem oil for root rot.
Interestingly, Azadirachtin is very effective against soil-dwelling pests and pathogenic organisms, but it does not harm friendly fauna such as earthworms.
Applying Neem oil in soil for your tomato plants is an excellent idea because they are especially likely to have nematode problems.
How To Mix A Neem Oil Soil Drench Recipe
To make an effective foliage spray and soil drench concoction to help fight against soil-dwelling pests and fungus, begin by following this recipe:
- One tablespoon of cold-pressed Neem oil
- One teaspoonful of dish castile soap
- One quart of warm water
Simply combine all of the ingredients and use it as a soil drench or plant spray about once a month as a preventative.
If you are treating an infestation, use for regular watering on a weekly basis until the problem is abated.
This same mixture is used as a foliar spray.
How Much Neem Oil Soil Drench Should You Mix up at Once?
Only mix up the amount you will use at one go.
Once the Neem oil is combined with water and dish soap, it will begin to degrade.
Keep full-strength neem oil in your refrigerator for as long as a year.
#1 – Carnivorous Plants Cannot Tolerate Soap!
If you are treating carnivorous plants, you should not use dish soap or any other type of soap.
The purpose of the soap is to act as an emulsifier.
This helps to distribute the oil throughout the warm water, so it spreads evenly through the soil.
If you eliminate the soap, simply use slightly warmer water and slightly warmed oil.
Stir or shake vigorously before applying.
#2 – Do A Patch Test
No matter what type of plant you are treating, it’s a good idea to do a little test to make sure the plant will respond favorably.
If using the mixture as a foliage spray, just treat a small portion of the plant and wait twenty-four hours to see how it responds.
If using it as a drench, treat just one plant (if you have several of the same types) and observe it for twenty-four hours before treating all of your plants.
Alternately, you may wish to use a diluted solution the first time to gauge your plants’ response.
#3 – Neem Oil Insecticide As A Soil Drench For Cannabis Is NOT The Best Choice
If you’re growing marijuana, you may find Neem oil negatively impacts the flavor of the product.
Some cannabis growers find Neem seed meal is a better alternative for controlling soil-dwelling insects.
The Neem seed meal not only discourages and negatively impacts soil pests, but it also provides a good dose of nitrogen and acts as a beneficial fertilizer.
Its NPK rating is 6 – 1 – 2.
Where Can You Get Neem Oil Spray?
Neem is an excellent SAFE, NATURAL pesticide and insecticidal soap solution mixed with water for pest problems around the home.
Pick up Neem Oil or organic pest control at your local garden center or online at Amazon.