Neem oil is a naturally occurring pesticide found in seeds from the neem tree. It is an excellent organic insecticide that can be used to control a wide variety of pests in your home garden. Neem oil works by disrupting the life cycle of insects in various ways, acting as an insect repellent, insect growth regulator, and oviposition deterrent. When used properly, neem oil can safely and effectively control insects while having very little impact on beneficial insects, birds, and mammals.
Benefits of Using Neem Oil as an Insecticide
Using neem oil as an organic insecticide has many benefits:
- Natural and non-toxic: Neem oil comes from the seeds of the neem tree, so it is completely natural and safe for people, pets, and the environment. It breaks down quickly and contains no toxic compounds.
- Multi-purpose pest control: Neem oil is effective against a broad range of common garden pests including aphids, whiteflies, snails, nematodes, mealybugs, cabbage worms, gnats, mites, and Japanese beetles.
- Works on contact: Neem oil kills insects right away upon direct contact. It also acts as a repellent to prevent reinfestation.
- Long residual effects: Neem oil can continue working for up to 14 days after application. This provides long-term pest protection without the need for repeated spraying.
- Low toxicity for bees: Neem oil will not harm honey bees and other beneficial pollinators when used properly and allowed to dry completely before bees are active again.
- Prevents insect growth and reproduction: Neem oil reduces insect fecundity and fertility by interrupting the insect growth cycle. It’s effective against all larval, pupal, and nymphal stages.
How Neem Oil Works on Insects
Neem oil works against insects in several ways:
Repels Insects
The strong aroma of neem oil masks the attractant odors that lure insects to plants. This causes them to lose interest in treated plants and look elsewhere for hosts.
Disrupts Molting
Neem oil can prevent immature insect life stages from reaching adulthood by interrupting the molting process. This leads to death at the larval or nymphal stage.
Reduces Fecundity
Neem oil reduces insects’ reproductive capabilities in two ways:
- It acts as an oviposition deterrent, preventing female insects from laying eggs on treated plants.
- It reduces viable egg production in females due to its impact on hormones involved in reproduction.
Stops Feeding
Neem oil has an antifeedant effect, meaning insects stop eating treated foliage or fruit. Starvation due to lack of feeding can lead to insect mortality.
Causes Malformations
Ingestion of neem oil may disrupt the hormonal balance required for normal growth in immature insects. This can cause deformities and death.
How to Make Neem Oil Spray at Home
Making homemade neem oil spray is simple. Here are two basic recipes:
Simple Neem Oil Spray
- 1/2 oz neem oil
- 1/2 tsp mild liquid soap
- 1 gallon water
Mix the ingredients well and pour into a spray bottle. Shake before each use.
Emulsified Neem Oil Spray
- 1 oz neem oil
- 1 tsp liquid soap
- 1 egg yolk
- 2 cups water
Blend the egg yolk and soap into the neem oil first. Slowly add water while continuing to blend into a creamy emulsion. Pour into a spray bottle.
Tips for homemade neem oil spray:
- Use pure cold-pressed neem oil. Avoid products with chemical solvents.
- The soap helps the oil mix with and stick to the water. Use a gentle soap like castile soap.
- Store unused spray in the refrigerator and shake well before using. It will keep for up to 2 weeks.
- Spray in the early morning or evening when pollinators are less active.
When and How Often to Apply Neem Oil Insecticide
Timing and frequency of neem oil application depends on which insect pests you are targeting:
For Preventive Pest Control
- Apply neem oil once every 7-14 days during the growing season.
- Spray early in the growing season before pests become established.
- Mist all leaf surfaces until just dripping. Cover the undersides of leaves.
- Reapply after rain or watering. Neem oil washes off easily.
For Existing Pest Infestations
- Spray neem oil every 5-7 days for 2-3 weeks.
- Use higher neem concentrations for heavy infestations.
- Target nymphs and larvae before they reach maturity and can reproduce.
- Combine neem oil with insecticidal soaps or pyrethrins to improve efficacy.
- Keep spraying at 5-7 day intervals for 2 weeks after the infestation clears.
As a Dormant Winter Spray
- Spray neem oil over dormant trees and shrubs in fall or early spring.
- Use higher neem oil concentration for overwintering pest eggs and larvae.
- Combine with horticultural oils for added impact and smothering effect.
- The neem residue will remain effective for 2-3 weeks after spring growth starts.
How to Apply Neem Oil Insecticide
Follow these guidelines to apply neem oil spray properly:
- Read label directions – Not all neem oil products are the same. Follow usage guidelines specific to your product.
- Use the right equipment – Apply neem oil using a tank sprayer, hose-end sprayer, or spray bottle as appropriate for your garden size. Avoid wiping leaves.
- Spray early or late – Apply neem oil early in the morning or at dusk to avoid harming pollinators. Let dry completely before bees become active again.
- Don’t over-apply – Excessive neem oil can damage plant tissues. Stick to the recommended dilution rate.
- Cover all surfaces – Neem oil must contact insects to be effective. Spray the tops and undersides of leaves, stems, flowers, and fruits.
- Add a spreader-sticker – These adjuvants help neem oil coat and stick to plants. Products like liquid dish soap also work.
- Reapply frequently – Neem oil washes off with rain or watering. Reapply every 5-7 days to maintain pest control.
How to Store Leftover Neem Oil Spray
To save leftover neem spray for future use:
- Pour unused neem oil spray back into its original container. Avoid cross contaminating with other pesticides.
- Add a label with the date and neem oil percentage if diluted. A permanent marker works well.
- Store in a cool dark place like a garage or shed. Avoid freezing or overheating.
- Neem oil spray can keep for up to 2 months if stored properly.
- Always shake or stir well before reusing to remix the ingredients.
- If spray sits for months, test on a few leaves first to check for phytotoxicity before wide application.
- If neem oil separates or solidifies, don’t reuse. Dispose of properly and mix a fresh batch.
Proper storage keeps neem oil viable for a long time. Follow these tips to avoid waste and get the most from your neem insecticide supply.
Plants and Crops to Use Neem Oil On
Neem oil is a versatile pesticide that can be safely used on a wide range of plants:
Vegetables: Tomatoes, potatoes, broccoli, squash, cucumbers, carrots, cabbage, cauliflower, kale, collards, spinach, beans, peas, artichokes, asparagus
Fruits: Apples, pears, peaches, plums, apricots, cherries, citrus, melons, berries
Herbs & Flowers: Roses, daisies, lilacs, sunflowers, dahlias, basil, mint, oregano, garlic, onions
Shrubs & Trees: Oak, maple, willow, hemlock, cypress, cedar, ash, forsythia, spruce, birch
Houseplants: Ferns, dracaena, palm, ivy, ficus, orchids, philodendrons, poinsettia
Always test neem oil on a few leaves first to check a specific plant variety’s tolerance before widespread spraying. Avoid getting neem oil on plant flowers where possible.
Pests Controlled by Neem Oil
Neem oil insecticide is effective against a remarkably wide range of troublesome garden pests:
- Aphids
- Whiteflies
- Mealybugs
- Scale
- Thrips
- Psyllids
- Lace bugs
- Leafhoppers
- Caterpillars
- Beetles
- Weevils
- Borers
- Leafminers
- Spider mites
- Nematodes
- Japanese beetles
- Snails and slugs
It can also deter or limit damage from deer, rabbits, and many other mammal pests. Neem oil is not effective on larger animals like groundhogs, squirrels, and raccoons.
How Effective Is Neem Oil For Specific Pests?
The effectiveness of neem oil varies somewhat by pest:
- Aphids: Highly effective against all life stages, especially early instars. Prevents reproduction. Causes mortality via antifeedant and hormonal activity.
- Whiteflies: Kills nymphs on contact. Repels and reduces oviposition in adults. Best applied early before heavy infestations build.
- Mealybugs: Foliar sprays less effective on waxy coatings. Better to spray colony areas and drench soil to reach root mealies.
- Thrips: Works best on larvae and nymphs. Contact sprays less effective on thrips deep in flowers or buds. Combine with spinosad or pyrethrins.
- Scales: Better results with crawler stage. Established armored scales need repeat applications. Include a penetrating adjuvant. Also scrape off established scales first.
- Mites: Effective against all life stages by disrupting molting. Also repels and reduces female reproduction. Avoid excessive applications.
- Beetles: Works well on larvae and chewing adults. Acts more as repellent on heavily sclerotized beetles. Japanese beetles are strongly deterred.
- Caterpillars: Most effective on younger instars before extensive feeding damage. Works via antifeedant and hormonal activity.
Using Neem Oil Safely
When using any pesticide, it’s important to follow some basic safety guidelines:
- Read and follow all label directions for your specific neem oil product.
- Avoid contact with eyes and skin. Wear gloves, long sleeves, pants, and eye protection when mixing and spraying neem oil.
- Do not ingest neem oil. Avoid inhaling spray mist.
- Keep children and pets away from plants until neem oil spray has dried.
- Apply early in the morning or at dusk to avoid harming bees and other beneficial insects.
- Never spray neem oil on plants in full sun or when temperatures exceed 90 ̊F. It can burn foliage.
- Rinse spray equipment thoroughly after use and avoid contaminating wells or waterways with neem residues.
- Store neem oil out of reach of children and pets.
When used properly following label directions, neem oil is very safe for gardens, people, pets and the environment. But always take basic precautions to avoid potential issues.
FAQs about Using Neem Oil Insecticide
Is neem oil safe for edible plants and vegetables?
Yes, neem oil is approved for use on all edible crops when applied according to label directions. It breaks down quickly and poses no risk of dietary toxicity. Always wait 1-2 days after last spraying before harvesting.
How long does neem oil last on plant foliage?
Neem oil begins breaking down immediately but provides residual pest control for 5-7 days typically. It can last up to 14 days on some surfaces. Reapply weekly for ongoing pest prevention.
Does neem oil kill beneficial insects like ladybugs?
No, neem oil is relatively non-toxic to most beneficial insects, especially once it has dried. It mainly impacts juvenile growth stages of pest insects. Avoid spraying neem directly on beneficials where possible.
Should neem oil be alternated with other insecticides?
Rotating neem oil with different mode-of-action insecticides can help prevent pest resistance. But this is usually not necessary given neem’s complex, multi-faceted activity on insects.
How long does it take for neem oil to kill insects?
Neem oil kills soft-bodied insects like aphids, whiteflies and mites on contact. It may take several days to kill tougher pests or those with waxy coatings. Effects on reproduction and growth take longer to manifest.
Can neem oil damage my plants if overapplied?
Yes, excessive neem oil use can potentially burn leaves and fruits or cause other unintended plant stress. Carefully follow label dilution rates and frequency guidelines.
How do I know if a pest outbreak is resistant to neem oil?
If correctly applied neem sprays repeatedly fail to control a particular pest, resistance may be developing. Try switching to a different class of insecticide with a different mode of action.
Conclusion
Neem oil insecticide offers gardeners a safe, effective, and environmentally-friendly pest control option for hundreds of plant species and dozens of common insect pests. It uniquely impacts multiple stages of insect growth and reproduction to provide both immediate kill and lasting residual activity. With proper timing and application technique, neem oil can form the cornerstone of an integrated pest management plan for home gardens and commercial growing. By harnessing the potent properties of the neem tree, we can protect our harvests from damage while nurturing the web of life in the garden.