How to use Neem oil on tomatoes (and other plants)

Here in this article we will show you how to make and use your own Neem oil spray and explain why it is better to only use 100% pure and unrefined organic cold pressed Neem oil.

We will also discuss why we feel Neem oil is the best and safest alternative for our tomato plants.

After all, it is every gardeners dream to find a pesticide that is safe on the environment and effective on pests. And for us, Neem oil has been the answer.

Neem oil does not just work as a natural pesticide but also as a fungicide and systemic insecticide. As the Neem oil is absorbed by the plant it works to protect the plant from pest attacks and infestations.

But first, what is this Neem oil people are talking about.

In India, Neem still today plays a role in areas as diverse as agriculture, fertilizer, pest control and many other areas of life.[1]

What is Neem oil?

Applying Neem oil mixture on tomato plants in grow bags
Spraying tomato plants in homemade grow bags

Neem oil is the vegetable oil pressed from the seeds of the Neem tree (Azadirachta indica), native to India and large parts of the Indian subcontinent.

Is is said that the Neem tree was India’s best kept secret at a time when the country was envied for its black pepper, cardamom, saffron and turmeric.

We discovered Neem many years ago when it was suggested to us as a natural pesticide to treat and protect our tomato plants from pests.

And we have been using Neem oil to kill pests ever since with great success. And not only to protect our tomatoes but also for other plants. But we do have our own preferred method.

How does Neem oil actually work?

Neem oil has been used for hundreds of years to control pests and diseases [4]. And it is easy to understand why as it works to fight pests and infestations in a number of ways including:

  • acts to reduce insects desire to feed
  • works as a repellent
  • interferes with the hormone system of insects affecting their ability to grow and lay eggs
  • repels and reduces the feeding of nematodes

Purchase Neem oil or make your own mixture?

We only use 100% pure and unrefined organic cold pressed Neem oil [2]. And we always make our own water based mixture.

Cold pressed is important as it is the method that preserves most of the beneficial compounds found in Neem. As for pure, organic and unrefined it is simply the best way to ensure that no potentially harmful additives are added to the oil.

And using Neem oil solution has been effective to the point where we never have had to use Neem cakes, clarified hydrophobic Neem oil products or any other ready mixed solutions containing Neem.

Also, why purchase Neem oil products that are ready mixed and often more expensive. After all, it is so easy to make your own pure Neem oil mixture.

Besides being effective, we really like that Neem is a natural product. Why would we want a ready made solution introducing any other potentially harmful and not natural ingredient?

We do also use Neem oil for soil soak but not for tomato plants as they are often too big to handle easily. But soil soak is an effective method to fight for example fungus gnats.

How to make Neem oil spray for tomato plants

100% cold pressed Neem oil is solid in room temperature and is not meant to be used on tomato plants unless heavily diluted.

Our Neem oil solution for our tomato plants is a simple 3 ingredient mix. And the reason for the third ingredient is simply that oil and water do not mix well. As you can se, we only use small amounts of Neem and the mixed solution is very diluted.

You will need:

  • 5 ml 100% pure, unrefined organic cold pressed Neem oil
  • 5 ml organic soap
  • 1 liter of warm water

Mixing the Neem oil solution for tomato plants:

I highly recommend using an organic soap. Today it is not difficult to find an all natural soap made from natural ingredients.

  • Warm your Neem oil gently. Cold Neem oil is solid and hard to work with.
  • Mix Neem oil and organic soap with warm water and stir to dissolve. Add more sop as needed but do not add too much soap as it may leave a residue on leavesand expose plant to sunburn.
  • When solution is mixed, pour into spray bottle to make applying neem oil easier.

How to apply Neem oil on tomato plants?

Neem oil mixtures work as a foliar spray where the solution is sprayed on the leaves or foliage. Unlike the more traditional methods where roots absorb for example fertilizers, it is the leaves or foliage that absorb a foliar spray.

Neem oil should be used late evening or early morning before your natural pollinators go to work. Simply spray at dusk or dawn when pollinators are not present.

Neem oil has not been found to have any adverse effects to beneficial insects like bees when used responsibly. When the oil spray dries it does not have much effect and becomes safe for pollinators, insects and bugs. [3]

But it is important to use diluted spray and never to spray the solution on a tomato plant that is stressed due to, for example, being transplanted to a larger pot.

Also, never apply Neem oil to tomato plants that are exposed to direct sunlight.

We use a spray bottle to apply the mixture and always make sure to cover the entire plant. Take your time and ensure that you reach every nook and cranny including the underside of every single leaf.

We have never applied Neem oil spay to tomato plants with fruits. From our experience, tomato plants with fruits are stronger than younger plants and we have found it enough to pinch leaves affected by pests or bugs.

Is there not a risk that you end up with “Neem oil tomatoes”?

Treating tomato plants with Neem oil will not cause the tomatoes to taste of Neem oil if applied properly.

Neem oil is a natural product and it is safe to use on plants with tomatoes [3]. Just follow instructions on packaging and make sure

  • not to use Neem oil for 72 hours before harvesting
  • always rinse tomatoes thoroughly after harvesting

But is Neem oil safe to use?

Here Neem oil used with ginger and turmeric
Using Neem with ginger and turmeric plants

We use Neem oil and we are consequently confident that Neem oil is safe for our use when used responsibly.

And we use it for most of our plants and vegetables when needed.

But it is inevitably up to you to make up your own mind.

On the one hand Neem oil sprays and other horticultural oils are seen as safe natural pesticides to fight pests on plants in most countries.

But there are also to my knowledge at least two notable exceptions. In both the UK and Canada Neem oil is banned as the active ingredient Azadirachtin has been found to be slightly toxic to fish and other marine life [4].

So is Neem oil safe to use? We believe it is safe when used responsibly. But you you need to decide for yourself. And as always, using a pesticide to fight pests in your garden should always be the last step and avoided when possible.

What are the benefits of using Neem oil

There are several benefits to using any environmentally friendly horticultural oil. Some of the benefits of using Neem oil spray are:

  • it is an effective pesticide for use on plants against aphids, powdery mildew, thrips, whiteflies, mites, fungus gnats, beetles, moth larvae, mushroom flies, leaf miners and nematodes.
  • very easy to use and inexpensive compared to many other products
  • no reported adverse effect on pets, earthworms, insects or pollinators when used correctly

But are there no disadvantages?

There are of course also factors that could be seen as disadvantages.

First, as we have already mentioned, the substance is banned in the UK and Canada due to slight toxicity to marine wildlife.

Also, the spray solution we use works really well. But it is nowhere near as fast to work as many commercial alternatives and it often requires several application to be effective.

Using Neem oil as a pesticide on our tomato plants
Neem oil and a selection of spray bottles with cherry and beefsteak tomato plants

[1] https://neemfoundation.org/about-neem/history-of-usage/

[2] https://www3.epa.gov/pesticides/chem_search/reg_actions/registration/fs_PC-025006_07-Apr-10.pdf

[3] https://www.canr.msu.edu/news/how-to-control-invasive-pests-while-protecting-pollinators-and-other-beneficial-insects

[4] http://npic.orst.edu/factsheets/neemgen.html

Meet the author: Mattias is an experienced gardener spending most of his free time on his knees among herbs, plants and garden vegetables. For the past two years he has been sharing gardening projects and how-to tutorials on the NordicLavender website and YouTube channel.