Neem oil when used as a soil drench is an extremely useful “natural insecticide” coming from the nuts of the Neem tree.
The oil has many active ingredients. The most notable ingredient is the naturally pesticidal compound called Azadirachtin, an extremely useful compound for combating a wide variety of plant insect pests such as:
- Fungus Gnats Larvae – read Neem Oil soil drench for Fungus Gnats
- 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 below-ground 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 oil drench works as a systemic insecticide even on fruit trees.
This means the plant absorbs the effective ingredient in the Neem oil soil soak (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 pesticide ingredient.
As a bonus, Azadirachtin also helps protect plants against fungal diseases when used in this manner. Some of the fungal infections include:
- Powdery Mildew
- Black Spot
- Leaf Spot
This means using Neem oil root drench as a preventative measure can help defend your plants from soil-dwelling larvae and problems such as root rot and bacteria. Check out these tips on using Neem oil for root rot.
Interestingly, Azadirachtin is effective against soil-dwelling pests and pathogenic organisms, but it does not harm friendly fauna like 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 Neem Oil Soil Drench Recipe?
To make an effective foliage spray and Neem oil soak to help fight against soil-dwelling pests and fungus, begin by following this Neem oil drench 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 the neem soil drench or foliar application by spraying leaves, and stems about once a month as a preventative.
If you are treating an infestation, use neem oil with your regular watering on a weekly basis until the problem is abated. This same mixture is used as a foliar spray.
How Much Neem Oil Drench Should You Mix Up at Once?
Only mix up the amount you will use in 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 liquid 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.
Related: Using Neem Powder On Plants
#2 – Use Neem Oil And Do A Patch Test
No matter what plant you are treating, it’s a good idea to know how to apply neem oil to soil and do a little test to ensure the plant will respond favorably.
If using the mixture as a foliage spray, take the spray bottle and treat a small portion of the plant. Then wait 24 hours to see how the plant 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 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.