Overview of Neem
Azadirachta indica, or simply Neem, is a drought-resistant evergreen tree that belongs to the Meliaceae, the Mahogany family of flowering plants, Meliaceae. It is characterized by a short trunk and a thick furrowed bark which supports a wide green canopy. Nicknamed “nature’s pharmacy”, it has a well-earned reputation for being the most potent medicinal flora in the world, producing remedies that date back to thousands of years before Christ. The tree has beneficial effects against antibiotic resistance, mosquito-borne diseases, diabetes, and cancer. Also, Neem extracts have potential in the cosmetic sector to treat skin conditions, hair strength, and oral health. More recently, the United Nations declared Neem the “Tree of the 21st Century” because of its growing benefits in not only healthcare but also the agricultural and environmental sectors. For instance, the tree itself can help combat climate change by sequestering large amounts of carbon from the atmosphere.
Even though Neem is native to the Indian subcontinent, it has been distributed in similar climates, mostly in tropical and subtropical regions, as people are beginning to recognize its diverse usefulness.
Neem Oil
Neem oil is the core ingredient for most neem-based products, and it is obtained mostly from seeds and kernels. It can be acquired through four methods: cold pressing, steam pressure extraction, solvent extraction and aqueous extraction. These extraction methods produce oils that differ in color and composition, each used for a different cause.
Neem as a biopesticide
There are over 140 biologically active compounds in the plant, the most prominent one being azadirachtin. The latter is found in the extracted oil which gives it its pesticidal properties. Being the most active ingredient in the plant, azadirachtin is very effective in targeting more than 500 different pest species. Hence, neem oil is categorized as a broad-spectrum pesticide. The biopesticide is mostly effective on pests that feed on plant foliage like aphids, mealybugs, scale, spider mites and whiteflies. It is also used to control leafhoppers, mites, nematodes and caterpillars.
Once applied, neem oil employs repelling, growth-inhibiting and antifeedant properties. Instead of immediately killing the pest, it disrupts the insect life cycle until it is unable to grow and reproduce. Unlike toxic pesticides, azadirachtin acts on the hormonal system of insects rather than the digestive and nervous systems, thereby eliminating the possibility of building resistance in future insect generations. Besides having a great advantage in eliminating pests, neem-based biopesticides can be used to treat fungal and bacterial diseases like powdery mildew, anthracnose, scab, black spot, rust fungi and botrytis, in addition Neem oil is a better pesticide due to its nematicidal activity. It is important to note that those biopesticides do not harm birds, mammals, earthworms, or essential pollinators. Moreover, neem oil is superior to synthetic pesticides in that it is cost-effective and organic. It is also a biodegradable and eco-friendly product that doesn’t damage the soil and leaves no residue behind. All that is translated into long-term effects on farmers’ fields.
Guide for using neem oil
In the market, neem biopesticides can be found as granules or concentrates. In general, the oil must be diluted with water and a surfactant like dish soap to help break down oil molecules into smaller ones that can disperse in water. There are several ways of using neem oil:
- Dormant spray: applied when plants are dormant to kill overwintering larvae and eggs.
- Foliar spray: applied on the leaves as a repellant or to control infestations during the growing season.
- Soil drench: applied in the form of a systemic pesticide that is poured in the soil as a solution and absorbed by the plant. Sucking insects ingest it and are thus affected.
- For infestations, treatment must be repeated every 7 days until all pests are gone. However, for prevention, it is recommended to spray or drench every 3 weeks. Results start to appear after 4 to 7 days of application.
Even though neem does not harm beneficial pollinators, it is preferable to apply it early in the morning or late in the day when these insects are less active. Neem oil is safe for humans and pets, but direct contact can cause mild skin or eye irritation. It is important to test out a small area of the plant to ensure that it is not sensitive to neem oil. If plants are undergoing any type of stress (extreme weather, harsh sunlight, transplant, over or underwatering) or if they are newly planted, do not apply the biopesticide directly.
Neem and the future
All in all, applying organic pesticides has become a worldwide interest due to its increasing potential in controlling pests whilst sparing beneficial pollinators, mammals and the surrounding environment. There is no doubt that the neem tree has presented many solutions to combat this century’s challenges. Moreover, the National Research Council in the United States chose neem to be one of their top ten plants which will be further investigated to be used in a sustainable future. This will not only intensify the value of neem, but it will also open a door for the tree’s future discoveries and uses.