How to apply neem oil to tomato plants

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Have you been thinking about using neem oil on your tomato plants? Neem oil is a versatile, natural product that all organic gardeners should have on hand, especially when growing tomatoes! 

Not only does neem oil help repel common tomato pests, but it controls fungal and bacterial diseases as well. However, not all neem oil is created equal (there are some imposter products out there!) and careful application at timely intervals is key.

In this article, we’ll chat about how neem oil works, the risks and benefits of using it, how to apply it to your tomato plants for best results and where to buy the highest quality product.

Let’s dive in!

What is Neem Oil?

Neem oil is a common product used in organic gardening and is pressed from the seeds and fruit of the fast-growing neem tree (Azadirachta indica). The fruit are smooth-skinned and look a lot like green olives with yellowish pulp inside. The neem tree currently grows in southern Africa, Australia, SE Asia and India. 

Active compounds in neem oil

Neem oil actually has over 100 active compounds, but here are the two that are well-known for their benefits in the garden:

• Azadirachtin: Effectively repels many garden pests, yet it will not harm beneficial insects like butterflies, honeybees or ladybugs as long as it is applied properly
• Nimbin: Inhibits the overgrowth of fungus and bacteria

Benefits of Using Neem Oil on Tomato Plants

Using neem oil on your tomato plants will really help them thrive! As I briefly mentioned above, neem oil can be very effective in not only repelling garden pests from your tomatoes, but disease as well! Plus, it is one of the least toxic products to vertebrates and beneficial organisms. Let’s break down the benefits!

Insecticide

One of the most well-known benefits of neem is its broad spectrum effects against common garden pests. First, it acts as an appetite suppressant, weakening the insect and of course, reducing the amount of plant damage. It also affects the insect’s life cycle from hormone function and molting to fertility and development. Lastly, it limits their movement and ability to fly.

Fungicide & Bactericide

Tomatoes are unfortunately prone to several diseases like blight, anthracnose, and wilt, so incorporating neem can be a big help. While you can use neem routinely as a disease-preventative, I’m not a big fan of routinely spraying any type of product (even organic neem!). I prefer to watch my plants and only use treatments as needed. 

Check out all of the diseases that neem oil can eradicate!

Nematicide

Root-knot nematodes can be particularly harmful to tomato plants. An infected plant’s roots will appear like they have knots all along the roots, making them ineffective at absorbing vital nutrients and moisture. Thankfully, neem is very effective at controlling these damaging pests as well (Sivakumar, 2011)!

Fertilizer

Neem is such an incredible product because even the leftovers from extracting neem oil are usable! There is literally no waste when it comes to neem! 

These dry, cake-like byproducts serve as an excellent, nitrogen-rich fertilizer, while also reducing soil-borne diseases. Tomatoes are heavy feeders, so your plants would certainly thrive with the addition of some neem seed meal.

The Homesteading RD's Product Picks
	A 6-1-2 slow-release, nitrogen-rich fertilizer that is cold pressed from the seeds of the fast growing Neem Tree. Can be mixed into soils or potting media, used as a top dress around established plants or steeped to make a potent liquid solution that is good for both leafy greens and young plants

Negatives of Using Neem Oil on Tomato Plants

While there are a lot of great benefits of using neem oil on your tomatoes, there are a few potential negatives that you should be aware of before you start spraying.

Effect is gradual

If you are expecting all of your garden pests to magically disappear within 30 minutes of applying, you will be disappointed. Neem is a gentle product that takes time to work compared to conventional insecticides. Try to be patient and it will make an impact with continued applications.

Requires multiple applications

As mentioned above, neem takes time to work, so it needs to be reapplied in regular intervals so that it can make a lasting impact. Neem should be reapplied after overhead watering your garden, or after rain. Also, neem is easily degraded by sunlight and natural microbes in the soil, so it should be reapplied every 7-14 days.

It is toxic to some animals

Fish and other aquatic animals are sensitive to the active compound, azadirachtin (NPIC). Because of this, neem oil is actually banned in the UK and Canada. If your garden is located near a water source with fish or other aquatic animals, consider using another product or ensure that you are only spraying on a calm day and limit overspray. Definitely do not spray this on acquatic plants.

It might impact beneficial insects

Neem oil only works as an insecticide when it is consumed. Therefore, the only insects that theoretically are affected are those that chomp away on your plants all day (the pests). Beneficial insects like bees, butterflies and ladybugs typically are only there to gather pollen or to feast on prey, so they shouldn’t be affected by neem.

However, you could directly spray on a beneficial insect (which is harmful), or a honeybee might pick up some wet neem oil on the blooms when looking for pollen. Therefore, it’s best to apply neem at dusk when there’s less beneficial insects out and about. Once the neem oil is dry, it’s completely safe. I also try to avoid the flowers, if possible. 

Types of neem oil

Not all neem oil is created equal, just like the oils that are available in our grocery stores! If you want to take a deep dive into the fascinating and controversial topic of fat, check out my article The Saturated Fat Controversy. 

Cold pressed neem oil

This is what we’re looking for in a neem oil product. Cold pressed means that the fruit is pressed with minimal processing, heat, and chemicals.  This results in a highly potent, clean product with the active ingredients left intact. The neem oil product below is what I personally use and recommend.

The Homesteading RD's Product Picks
	This is THE best neem oil on the market. The oil is cold-pressed without any use of heat or chemical additives to retain the purity, essential nutrients and potent azadirachtin content to ensure that you are getting the best results.

Other forms of neem oil

Other types that you’ll see on the market are clarified hydrophobic extract of neem oil and azadirachtin extract neem oil. These extracts are highly processed and have lost many of the beneficial compounds in the process. 

These false products are more common than you think! I dug around in my gardening cupboard out of curiosity and found an old bottle of neem. Sure enough, it’s the clarified hydrophobic extract form. I was fooled, too!

The best neem oil products are concentrates, so you will need to dilute them with water and add soap (an emulsifier) in order to make an effective spray. I’ll show you exactly how to do this! Neem degrades quickly, so I recommend only mixing up how much you really need and making a fresh batch each time.

Supplies Needed

• Gloves and protective eyewear
• Neem oil – cold pressed
• Water
• 1 gallon sprayer
• Castile liquid soap – essential for emulsifying the water and neem oil!

The Homesteading RD's Product Picks
	This is THE best neem oil on the market. The oil is cold-pressed without any use of heat or chemical additives to retain the purity, essential nutrients and potent azadirachtin content to ensure that you are getting the best results.
	This garden sprayer makes application of neem oil a breeze! It features a wide funnel top for easy pouring and a handle for easy pumping and handeling. The long 12" hose makes it easy for you to reach all areas of your plants. Adjustable spray from stream to mist.
	This Nature's Gold castile soap is made with organic, sustainable ingredients and is the perfect addition to your neem oil spray mixture! Provides a luxurious lather without synthetic preservatives, thickeners, or foaming agents. Castile soap is so versitile on the homestead - think handsoap, facewash, laundry soap, pet shampoo, you name it!

How to apply neem oil

Always defer to the product instructions on the bottle for mixing and application details, but here are some general guidelines to follow for neem oil administration.

• Step 1: Put on gloves and protective eyewear. Neem oil is non-toxic to humans, but it can be mildly irritating to the skin. To be honest though, I never gear-up when using neem oil and it’s never bothered me!
• Step 2: Prepare neem oil for tomato foliar spray by mixing 2 tsp of castile soap in 1 gallon of water – I like to mix directly inside my 1 gallon sprayer basin. Then, add 2 Tbsp neem oil. Mix well so that the neem oil is evenly dispersed in the soapy water. Pro tip: Neem oil loses its potency after just 8 hours, so only mix as much as you’ll realistically use that day.
  • ½ gallon: add 1 tsp of castile soap to ½ gallon of water, then add 1 Tbsp of neem oil.
  • 1 quart: add ½ tsp of castile soap to 1 quart of water, then add 1 ½ tsp of neem oil.
• Step 3: At dusk, apply the freshly-made neem oil mixture to your tomato plants using the fine mist setting on your sprayer. Try to achieve a light mist to coat all parts of the plant, especially the underside of the leaves (don’t drench it!). The spray wand makes reaching all angles a breeze! Dusk is preferred to avoid leaf burn (sun + neem = burn!) and the (small) potential impact on pollinators.
• Step 4: If you have any neem oil mixture leftover, don’t store it and don’t toss it out! Instead, immediately pour it around the base of any of the other plants in your garden – I personally wouldn’t add it to the base of the tomatoes I just sprayed, unless I had a severe infestation (see neem oil soil soak section below for details).
• Step 5: Rinse out your 1 gallon sprayer and store your neem oil concentrate in a cool, climate-controlled location. If you store the neem oil in your garden shed, it will quickly lose potency from the drastic temperature fluctuations. 
• Step 5: Mix up a fresh batch and reapply every 7-14 days until disease and/or pests are under control. Also, reapply after overhead watering or rainfall.

Alternative Treatment: Neem Oil Soil Soak

If using a foliar neem spray on your tomato plants isn’t your jam, try a neem oil soil soak instead! While soil soaks take longer to take effect than foliar spray, they are still quite effective in controlling pests and disease.

Simply whip up the diluted neem oil mixture that’s listed above and pour 2-3 cups of the mixture around the base of each plant. Repeat every 2-3 weeks.

FAQ About Neem Oil for Tomato Plants

How soon can I harvest my tomatoes after applying neem oil?

The general consensus is that you can safely harvest tomatoes 5-7 days after application. However, neem rapidly degrades after just 2 days in some conditions, so you may be able to harvest rather quickly. I recommend gently washing your tomatoes prior to consumption to be safe.

How often do I need to reapply neem oil to my tomato plants?

Neem oil rapidly breaks down, so it is recommended to reapply every 7-14 days. Reapplication is also necessary after overhead watering or after rainfall. 

Neem oil burned my leaves, what happened?

If neem oil burned the leaves of your tomato plant, consider the following tips to avoid it from happening again:

• Avoid applying in temperatures >90 degrees.
• Ensure that you are diluting it properly (2 Tbsp neem oil in 1 gallon of water, plus 2 tsp of soap).
• Avoid spraying during mid-day sun as this can result in burn. Dusk is preferred and is the best time to avoid beneficial pollinators as well!
• Nervous? Do a test leaf before spraying your entire plant.

Is neem oil toxic to humans?

Neem oil is non-toxic to humans, however I would keep it out of reach of children and never ingest it. It can be mildly irritating to the skin, so wearing cloves and eye protection when using is best.

In neem oil toxic to bees?

Neem oil is not inherently toxic to bees because bees do not chew on the leaves of plants. However, if neem oil is sprayed directly onto a bee, or if a bee picks up pollen from a flower that is still wet with neem oil, the bee could be harmed. Therefore, it’s best to always apply neem oil at dusk when the pollinators are out of the garden. Once neem is dry, it is safe.

Where can I buy neem oil?

Neem oil is widely available in the United States and many countries (except in the UK and Canada where it is banned due to toxicity to aquatic animals). However, as we discussed above, not all neem oil is created equal! The neem oil that I bought years ago from my local garden store is the clarified hydrophobic extract form. I was fooled, too! Below is the pure & highly-potent neem oil product that I personally use and recommend.

The Homesteading RD's Product Picks
	This is THE best neem oil on the market. The oil is cold-pressed without any use of heat or chemical additives to retain the purity, essential nutrients and potent azadirachtin content to ensure that you are getting the best results.

Other Articles You’ll Love

• Growing Tomatoes in Grow Bags – A Comprehensive Guide
• The 5 Best Soil pH Testers
• The Best Compost for Your Vegetable Garden

Final Thoughts

Neem oil is such a diverse product that can help your tomato plants thrive and effectively fight off pests and disease. The benefits don’t stop there, either! Neem oil can be used throughout your garden and even on your house plants. Happy gardening!

*Information in this article was referenced from personal experience and/or from my favorite gardening book The Vegetable Gardener’s Bible unless otherwise noted.