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Author Topic: Natural Pesticide: Neem Oil  (Read 1375 times)


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Natural Pesticide: Neem Oil
« on: February 20, 2016, 08:09:04 pm »

Neem oil is derived from Azadirachta indica. Neem oil is found in most parts if the plant, but the insecticidal compound is most concentrated in the seeds.

  • Neem does not typically kill insects, but rather it deters insects from eating whatever has been sprayed, and it acts as an egg-laying deterrent. The active ingredient of neem oil is azadirachtin, a limonoid compound. When insects eat neem oil, the azadirachtin creates hormonal imbalances causing a loss of appetite. Neem is also thought to prevent insect larvae from maturing and reduces or interrupts insect mating behaviors due to the imbalances caused. In some cases the neem oil will be lethal if it coats an insect's breathing holes, effectively suffocating it. It can be effective in controlling outbreaks of aphids, thrips, weevils, scale, whiteflies, mealybugs, cabbage worms, termites, etc. Spray every 7-10 days. Wait at least a week after the start of a neem oil treatment to assess effectiveness.
  • Can be used as a foliar spray, however it is recommended that you only apply in indirect light or in the evening to avoid burning leaves. A drought stressed plant can also be burned by foliar spray.
  • Can also be used as a fungicide against fungi, mildew, and rusts when applied as a 1% solution. It has also been shown to be effective against root rot, anthracnose, and sooty mold spots.
Dilution ratios: Please note the soap is to help the oil stay suspended in the water, without it the neem oil would separate out. Add soap to water first, then add oil to soapy water. Warmer water mixes better. Shake well and often!
  • Mix 1 teaspoon (5 ml) pure neem oil with 1/3 teaspoon (1-2 ml) insecticidal soap (or other detergent) into 1 quart or liter of water for a roughly 0.5% dilution.
  • Mix 6.5 oz (~185 g) neem oil with 5 teaspoons (25 ml) insecticidal soap with 4 gallons (~15 L) water for a 1% solution.
Some plants can be killed by neem oil, especially when used heavily. You can always test a small area of a plant to see how it reacts before using.

Concerns regarding the safety of neem oil with beneficial insects including bees have been studied, but most specify that it will only cause harm to smaller hives if used inappropriately, and in massive quantities. Since neem oil doesn't target leaf eating insects, most butterflies are considered unaffected by neem oil usage (as long as you're not directly spraying the insects). It is 'generally regarded as safe' by the EPA (for external use only).
« Last Edit: February 20, 2016, 08:12:06 pm by TBM »