Andre CampbellCaterpillar problems often start when a moth or butterfly lays eggs on or near a plant.
After the eggs hatch, the young caterpillars begin feeding. Some species can quickly chew holes in leaves and damage vegetables.
However, not every caterpillar is a garden pest. Some become helpful or beautiful butterflies and moths. Try to identify the caterpillar before deciding whether you need to control it.
If you find a harmful species, it is often easier to control while the caterpillars are still small.
As caterpillars eat, they grow larger and may cause more damage. Green caterpillars and other pest caterpillars can attack many garden plants, including kale, collards, cabbage, and tomatoes.
Homemade Sprays for Caterpillars
Below are 15 homemade sprays that gardeners use to help discourage or manage caterpillars. Some have stronger evidence than others, so results can vary.
Keep in mind: Homemade sprays do not always work the same way on every caterpillar or plant. Some are used mainly as deterrents rather than as insect killers.
Always test a homemade spray on a few leaves first and wait a day or two before treating the whole plant.
1. Homemade Oil Spray
A homemade oil spray may help control some small, soft-bodied garden pests. It may also discourage some caterpillars, but results can vary.
Mix one tablespoon of mild liquid soap with one cup of vegetable oil.
When ready to apply, combine two teaspoons of the mixture with a quart of water. Mix and apply the solution directly onto the plants.
2. Diatomaceous Earth
Diatomaceous earth (DE) is a fine powder made from the remains of tiny aquatic organisms. It may help control some crawling garden pests by damaging their protective outer layer and causing them to dry out.
It may also affect caterpillars that come into direct contact with the dry powder, but results can vary.
Some DE products can be mixed with water for easier application. If the product label allows this, mix and apply it according to the directions. DE only works after the water dries, leaving the powder behind.
You can also sprinkle DE directly on your plants and on the caterpillars that you see.
Avoid putting DE on flowers that bees and other helpful insects may come into contact with. Also avoid breathing in the dust.
3. Soap
A mild soap-and-water spray may help against some small, soft-bodied pests. It may also affect very small caterpillars when sprayed directly on them, but results can vary.
Mix one quart of water with 1.5 teaspoons of mild organic liquid soap. Shake well, then spray the solution directly onto the affected area.
Soapy water may deter caterpillars and can sometimes harm very small larvae. Aim to apply it in the evenings or early morning.
Test the mixture on a few leaves first. Some soaps can damage plants.
4. Garlic
Garlic has a strong smell and is often used in homemade garden sprays. It may help discourage some insects, but results can vary.
To make a natural caterpillar repellent using garlic, blend 2 whole garlic bulbs with 1/2 cup of water. Next, let the mixture sit for at least twelve hours.
When it’s ready, add one teaspoon of mild liquid soap and a quart of water to the mixture. Mix well, strain, and then spray.
You can also combine this deterrent spray with hot peppers to get rid of armyworms and cabbage worms.
5. Lavender Spray
Lavender has a strong scent that may help discourage some caterpillars and other garden pests.
Add one cup of fresh lavender leaves and flowers to two cups of hot water. Let the mixture steep for several hours or overnight.
Strain the liquid and add two more cups of water. Mix in a few drops of mild liquid soap to help the spray stick to plant leaves.
Pour it into a spray bottle and apply it to the tops and bottoms of affected leaves.
Test it on a small area first. Homemade plant sprays may damage sensitive plants.
6. Thyme Spray
Thyme has a strong scent and contains natural aromatic compounds. A homemade thyme spray may help discourage some garden pests, although it is not a proven caterpillar killer.
Add one cup of fresh thyme to two cups of hot water. Let the mixture steep for several hours or overnight.
Strain out the leaves and add two more cups of water. Mix in a few drops of mild liquid soap.
Pour the mixture into a spray bottle and lightly spray affected plants, including the undersides of leaves.
7. Chili Pepper
You can also use fresh chili peppers to make a spray for deterring caterpillars.
Blend half a cup of chopped chili peppers with two cups of water. Let the mixture sit overnight.
Strain it well and add a few drops of mild liquid soap. Dilute one cup of the mixture with one quart of water before spraying your plants.
However, wear gloves when preparing hot pepper spray. Keep it away from your eyes, nose, and mouth.
Test the spray on a small part of the plant before using it widely.
8. Citrus
Citrus peels contain strongly scented oils. Homemade citrus sprays are sometimes used to discourage garden pests, but they are not a proven caterpillar control like Bt.
To make a homemade citrus spray, grate the peel of one lemon or orange and place it in a container. Pour one pint of hot water over the peel and let the mixture sit overnight.
In the morning, strain it through cheesecloth. Then, spray the mixture onto the affected plants.
9. Mustard Spray
Mustard has a strong smell and contains compounds that may discourage some garden pests.
Mix one tablespoon of mustard powder with one quart of warm water. Allow it to sit for several hours.
Strain the mixture if needed, then add a few drops of mild liquid soap. Shake well before spraying it on affected plants.
Concentrate on areas where caterpillars are feeding. Test the mixture on a few leaves first, since homemade sprays may damage sensitive plants.
10. Sage Spray
Sage contains strongly scented natural oils that may help make plants less attractive to some feeding insects.
Chop one cup of fresh sage leaves and place them in a container. Pour two cups of hot water over the leaves and allow the mixture to steep overnight.
Strain out the leaves and dilute the liquid with two cups of water. Add a few drops of mild liquid soap and mix well.
Spray the mixture over affected plants, paying attention to areas where caterpillars are feeding.
Test a few leaves first and wait a day before spraying the entire plant. Results can vary, so use this spray as a deterrent rather than a proven caterpillar killer.
11. Ginger Spray
Ginger has a strong smell and contains natural plant compounds. A homemade ginger spray may help discourage some caterpillars from feeding, although results can vary.
Finely grate or blend two tablespoons of fresh ginger with two cups of warm water.
Allow the mixture to sit for several hours or overnight. Strain it well, then add a few drops of mild liquid soap.
Pour it into a spray bottle and spray affected leaves, including the undersides.
Test the spray on a small area first and wait at least a day before treating the whole plant.
12. Rosemary Spray
Rosemary has a strong scent and natural aromatic oils. A homemade rosemary spray may help discourage some garden pests, including caterpillars.
Chop about one cup of fresh rosemary leaves. Place them in a container and add two cups of hot water.
Allow the mixture to steep overnight.
Strain out the rosemary and add two more cups of water. Add a few drops of mild liquid soap to help the spray spread over the leaves.
Shake well and spray the affected plants. Apply it to the tops and bottoms of the leaves.
Test it on a few leaves first before spraying the entire plant.
13. Tomato Leaf
Tomato leaves are also sometimes used to make homemade pest sprays.
They contain natural alkaloids that may discourage some insects, but there is limited evidence that tomato leaf spray reliably controls caterpillars.
When the leaves are crushed, the alkaloids are released. Therefore, chop two cups of tomato leaves and steep them in one quart of water. Leave it overnight.
In the morning, strain the mixture and lightly spray the affected leaves.
14. Peppermint Oil Spray
Peppermint oil has a strong scent and is sometimes used in homemade pest sprays. However, there is limited evidence that it can reliably control caterpillars in a garden.
To give it a try, combine 10 to 15 drops of peppermint essential oil with one quart of water. Add a few drops of mild liquid soap to help the oil mix with the water.
Shake the solution well before spraying it on the plant leaves. Make sure to target the undersides, as pests often hide there.
Avoid spraying during the hottest part of the day. Essential oils can damage sensitive plants, especially when used too strongly or during hot, sunny weather.
15. Onion Spray
Onion has a strong smell and is sometimes added to homemade garden sprays. It may discourage some pests, but it is not as dependable for caterpillar control as Bt or spinosad.
To give this homemade spray a try, chop one medium onion and blend it with two cups of water. Let the mixture sit for several hours or overnight.
Strain the liquid through cheesecloth or a fine strainer, then add a few drops of mild liquid soap.
Pour the solution into a spray bottle and apply it lightly to affected plants. Reapply after heavy rain if needed.
Other Natural Caterpillar Control Methods
Below are some other natural ways to help keep caterpillars under control.
1. Hose ‘Em
Hosing is the most straightforward option. After all, you’re likely out there with the hose watering your plants anyway!
Use a strong stream of water to knock pest caterpillars from sturdy plants. After they fall, collect and dispose of them so they do not crawl back onto the plants.
2. Bacillus Thuringiensis (Bt) Spray
Bacillus thuringiensis var. kurstaki, often called Bt or Btk, is a biological pesticide used against many pest caterpillars.
The caterpillar must eat treated plant material for Bt to work. Young caterpillars are usually easier to control than large ones.
Spray the leaves thoroughly according to the product label, including areas where the caterpillars are feeding.
3. Azadirachtin/Neem-Based Insecticide
Azadirachtin is a compound derived from neem. It affects insect feeding, growth, and development.
Follow the product label carefully, including directions for crops, application rates, and harvest timing.
4. Spinosad
Spinosad is effective against many caterpillar species, sawfly larvae, and other pests.
Depending on the product label, spinosad can be used on many vegetables, fruits, and ornamental plants. It can control caterpillars, cutworms, leaf miners, spongy moth caterpillars, and several other pests.
Always check the label to make sure the product is approved for the plant and pest you want to treat.
However, spinosad can harm bees while it is wet. Avoid spraying flowers when bees are active, and always follow the pollinator precautions on the label.
Takeaway
Caterpillars can damage vegetables, flowers, and other garden plants when their numbers get too high. However, not every caterpillar needs to be removed.
First, identify the caterpillar and assess the damage it is causing. Hand-picking and other physical methods may be enough for small infestations.
If you need a proven caterpillar treatment, Bt is one of the best options for young pest caterpillars. Neem-based products and spinosad may also help when used correctly.
No matter which product you choose, always read the label first. Make sure it is safe to use on the plant you want to treat, especially when spraying vegetables or other edible crops.
Sasha Campbell
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