We’ve all been there… you have happy, thriving plants in your garden one day, and the next day you find devastation in the form of half-eaten leaves on your prized vegetable plants.
Although many bugs can be a nuisance in your garden by munching leaves and laying eggs, caterpillars can devour an astonishing amount of leaves in a very short time. This can spell disaster in your garden, as a shortage of healthy leaves on your vegetable plants will hinder the natural process of photosynthesis.
A plant bare of leaves is a plant at risk of dying.
Examine your plants closely, paying special attention to the leaves – often you can recognize the signs of a caterpillar infestation far earlier than you will see the caterpillars themselves… especially since some caterpillars are very well camouflaged.
1. Holes in the leaves beginning at the outer edges, working in toward the center – a caterpillar’s modus operandi.
2. Tiny black specks on the leaves’ surfaces – this is called “frass”, which is the waste caterpillars excrete.
3. A single tiny egg, or clusters of tiny, white eggs, usually found on the undersides of leaves. These eggs could be deposited by many types of bugs, but in conjunction with the symptoms described above, the presence of eggs points strongly to caterpillars.
4. Webs or cocoons – Usually found at junctures of tree branches, not garden plants, but this sign can indicate caterpillars in the area. As the larvae mature, tiny caterpillars will be visible through the web.
If you see these symptoms in your garden, the time to act is now. There are a few options to combat caterpillars in your garden by using organic methods.
Let’s talk about neem oil, first and foremost.
Does Neem Oil Kill Caterpillars?
Neem oil is an indispensable weapon for the organic gardener. Made from the seeds of the neem tree, neem oil is reported by the EPA to be safe for use on your edible plants. It is biodegradable, non-toxic, and if used correctly, it will not harm humans or pets, nor be a threat to your birds, bees, butterflies, and ladybugs.
It can be used to kill and repel over 170 species of insects, including all types of caterpillars.
Neem oil works in two ways. Simply due to its nature, neem oil can smother smaller insects on contact by blocking their airways, and when sprayed on caterpillars, it’s reported to also have the ability to work by dehydrating their soft bodies.
The second way neem oil works is when an insect ingests it by eating a plant that has been treated with a diluted neem oil spray or soil drench.
This is the result of the active ingredient, azadirachtin, which, once consumed, will disrupt an insect’s life cycle activities, causing them to stop feeding, stop breeding, and be unable to lay eggs.
Does it Kill Caterpillar Eggs?
Neem oil is thought to kill the brand-new larvae as soon as they emerge from the eggs, rather than the eggs themselves. This would be dependent on the oil still being wet enough, which is why you should plan on repeat applications of neem oil, instead of using a single treatment.
There is also a theory that newly hatched larvae might be dysfunctional, (unable to eat, etc.) if the eggs had been saturated with neem oil prior to hatching.
Does Neem Oil Prevent Caterpillars?
Neem oil can be used as a preventative measure to keep caterpillars from dining on your garden plants by altering the taste of the leaves. The oil has a strong garlicky/sulfuric odor, and according to research, most insects hate the taste of it.
By spraying neem oil on the leaves of your plants, you’ve suddenly made them less appetizing.
Since neem oil can be washed off by the rain, you should also consider simultaneously using it as a soil drench. Once your plant’s root system absorbs the neem oil, it will change the taste of the leaves.
An added benefit of the soil drench method is that the azadirachtin will still be present within the leaf’s cellular structure to affect the caterpillar’s hormonal system. Within a few days’ time, the caterpillar will die from starvation.
Should I Kill the Caterpillars in My Garden?
The decision to kill the caterpillars in your garden is a personal choice.
On one hand, caterpillars can be very destructive to a garden, voraciously consuming every leaf in sight. If you’re not vigilant, entire crops you’ve planted can be destroyed in a matter of weeks.
But… caterpillars turn into butterflies and moths, which are important to the natural world’s food chain, as well as being very efficient pollinators. In fact, moths have recently been found to be better pollinators than bees, according to this study.
If your conscience is torn, you can try picking caterpillars off your plants by hand, instead, and transfer them to an area of the yard away from the vegetable garden.
Good Caterpillars You Want vs Bad Caterpillars That Cause Issues
As we all know, some of the most beautiful butterflies were once lowly caterpillars. You might even be planting specific flowers for the purpose of attracting butterflies to your yard.
It’s important to realize that by attracting butterflies such as Monarchs and Swallowtails to your yard, that’s also where they’ll lay their eggs, which will soon become caterpillars. Do you want them in your vegetable garden? Probably not. You can choose to tolerate their presence, or you can choose to destroy them. You can also relocate them.
But what about the caterpillars that don’t turn into beautiful butterflies? There are plenty of those out there, including the dreaded hornworm (the bane of every tomato grower’s existence), and gypsy moth caterpillars, which, left unchecked, can destroy entire stands of trees, and strip the leaves from your flowering shrubs.
You’ll be better equipped to decide if you can identify caterpillars and be aware of what each type will turn into. Use this helpful visual guide to identify the caterpillars on your property.
How to Use Neem Oil to Kill or Prevent Caterpillars?
You can use neem oil as a foliar spray which will kill caterpillars on contact, and also use the same solution as a soil drench to repel caterpillars from eating the leaves.
Spray: To one quart of lukewarm water, add 1 teaspoon of 100% pure, cold-pressed neem oil, and a drop of liquid dish soap. Shake well and transfer the solution to a sprayer. Spray your plants thoroughly – all leaf surfaces, stems, and stalks, as well as the ground surrounding your plant.
Soil drench: Use the same recipe and pour 1 – 2 cups of the solution into the soil at the base of each plant.
How Often Should You Use Neem Oil for Caterpillar Prevention?
If spraying, repeat every 4 days for an active infestation, or once every 7 – 10 days as a preventative measure. Increase the time between applications if you see signs of foliage burn. Be aware that a hard rain will wash off your application.
For a soil drench, repeat the application once every 2 – 3 weeks. Azadirachtin will remain active in the soil for up to 21 days.
Can Neem Oil Damage My Plants?
As long as you follow a few guidelines, neem oil won’t hurt your plants.
- Always dilute neem oil. Used full strength, it will damage your plants.
- Never use neem oil spray during full daylight hours, as the combination of oil and sun will cause foliage burn. Applying neem oil sprays at dusk will also protect bees, who are less likely to be present.
- Never use neem oil on plants that are stressed from being newly transplanted, or over/underwatered.
- Avoid using neem oil on plants with wispy, thin, or delicate foliage, such as these.
What are Some Alternative Ways to Get Rid of Caterpillars in the Garden?
Besides neem oil, and hand-picking caterpillars off your plants, there are some other organic methods you can utilize.
- Bacillus Thuringiensis, known in the gardening world as “BT”, this a great organic option for getting rid of caterpillars in your garden. BT is a naturally occurring bacterium that, once ingested, creates a protein in the caterpillar’s digestive system that hinders its ability to eat, eventually starving it.
- Homemade Pepper Spray can kill caterpillars on contact. Combine 1/2 cup of chopped habanero peppers, 6 cloves of garlic, 2 cups of water, 1 Tablespoon of oil, and 1 teaspoon of liquid soap in a blender, and puree until smooth. Spray directly on caterpillars, as well as on leaves where you see signs of an infestation.
- Vinegar and Water Spray will kill caterpillars on contact. Combine 2 Tablespoons of white or cider vinegar with 1 gallon of water, and spray on affected plants.
It’s always a good idea to avoid attracting caterpillars and moths to your vegetable garden, to begin with. Try to utilize these tips.
1. Moths are attracted to light, so it’s best to plant your vegetable garden away from security lights or streetlights, and not to have lights on in your garden at night.
2. Plant flower gardens for pollinators in a different area of your yard.
3. Add cabbage moth decoys to your garden. Cabbage moths are territorial, and if a female moth sees the presence of another, she may move on before laying her eggs. You can purchase cabbage moth decoys
Read our related neem oil posts:
- Tackling Tiny Invaders: Will Neem Oil Kill Ants?
- Does Neem Oil Kill Fungus Gnats?
- Does Neem Oil Kill Ticks?
- Using Neem Oil on Fruit Trees
- Can You Spray Neem Oil on Flowering Plants?
Michelle Weaver is a former pastry chef of thirty years who reinvented herself during the pandemic, now happily earning a living through freelance writing and selling her art. She and her significant other live in an 1895 farmhouse in North Carolina, where they have several acres, allowing her to garden to her heart’s content. When she’s not playing in the dirt, she enjoys hiking in the nearby mountains, creating new vegetarian recipes, and photographing the wildlife that comes to visit.