Plant Taxonomy of Neem Oil Trees:
Plant taxonomy classifies the trees that Neem oil is derived from as Azadirachta indica A. Juss.
Plant Type for Neem Oil Tree:
What Is Neem Oil?:
Neem oil is pressed out of the seeds obtained from neem trees. In addition to its use as an organic insecticide spray, neem oil has been used medicinally and in the cosmetics industry. One purveyor of the product (Dyna-Gro) explains how neem oil works as an organic insecticide as follows: "It disrupts insects' hormonal balance so they die before they molt to the next life stage."
How Neem Oil Works:
According to the EPA, "Azadirachtin and Clarified Hydrophobic Extract of Neem Oil are derived from the natural oil found in seeds of the neem tree.... When the natural neem oil is removed from the seeds and treated with alcohol, virtually all of the azadirachtin and related substances separate from the oil itself. The remaining oil - without the azadirachtin - is called Clarified Hydrophobic Extract of Neem Oil. Azadirachtin acts in the following ways: It deters certain insects, such as locusts, from feeding and it interferes with the normal life cycle of insects, including feeding, molting, mating, and egg laying."
Neem Oil As Organic Insecticide: Pests Killed or Repelled:
Neem oil kills some pests (after they've eaten leaves sprayed with neem oil), while it repels others with its strong smell. Neem oil is used to control many pests, including whitefly, aphids, Japanese beetles, moth larvae, scale and spider mites. Because it kills mites -- which aren't insects but, instead, related to spiders and ticks -- neem oil is listed as a "miticide." Sprays containing clarified hydrophobic extract of neem oil are also used as fungicides against rust, black spot, mildew, leaf spot, scab, anthracnose, blight and botrytis.
Neem Oil As Organic Insecticide: How to Apply:
According to the people who sell the neem oil product that I tested ("70% Neem Oil"), "Mix 70% Neem Oil at the rate of 2 tablespoons (1 ounce) per gallon of water. Thoroughly mix solution and spray all plant surfaces (including undersides of leaves) until completely wet."
Neem Oil As Organic Insecticide: When to Apply:
When applied as a preventative, neem oil should be applied on a 7 to 14 day schedule, say the manufacturers of 70% Neem Oil. To control a pest or disease already present, they recommend an application of neem oil on a 7 day schedule.
Benefits of Neem Oil for Pest Control:
Besides being an organic insecticide, using neem oil allows you to target pests, specifically, as opposed to beneficial insects (e.g., bees and lady bugs). By definition, "pests" are the insects eating your plants, and neem oil, properly applied, kills an insect only if it ingests the sprayed foliage (bees and lady bugs don't eat plant leaves).
Origin of the Name, "Neem Oil":
Neem oil and the tree from which it is derived are so called from the from Sanskrit, nimba.
A Success Story Using Neem Oil -- And a Failure:
One day in May this year, I noticed that the ninebark shrub I had just planted the prior fall was covered with aphids. I sprayed 70% Neem Oil on the foliage (following the mixing directions cited above) every 7 days for 3 weeks, after which period I found no more aphids on the plant.
In July, however, I had less success using Neem oil to fight a pest invasion. Upon finding whitefly on my black hollyhock, I began treating the plant with Neem oil. I can't honestly say that the organic herbicide was of much help in dealing with my whitefly problem.
