How To Control The Caterpillars Eating Your Garden

Caterpillars represent the immature (larval stage) in the life cycle of moths and butterflies. Of course, butterflies are very desirable, beneficial insects and we don’t want to kill butterfly caterpillars. The types of caterpillars that do the most damage to autumn crops are the kind that become moths.

Moth caterpillars are introduced to your garden when a moth lays eggs on your plant leaves. You may see these eggs on the undersides of the leaves of your plants. Some moths lay single eggs, and others lay clusters of eggs. Naturally, each egg hatches to become a little caterpillar and the caterpillars set to work eating the food of their choice.

caterpillars eating leaves in the garden

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Very often food of their choice is also the food of your choice. If you have a lot of moth caterpillars in your garden, you can count on them doing a great deal of damage to your vegetable production and consuming quite a bit of your crop during the two or three weeks between their hatching and wrapping up in a cocoon.

This pupal stage varies in length. Some caterpillars emerge from their cocoons as moths in only few weeks. Others may stay in the cocoon through the winter and emerge in the springtime. Either way, when the caterpillars become moths they lay more eggs and start the whole cycle over again.

How Can You Tell If There Caterpillars In Your Garden?

Most caterpillars are big enough to see pretty easily, but another dead giveaway is that the leaves of your plants will begin to look ragged and filled with holes. When you see this, look at the underside of the leaves and you are sure to find caterpillars and possibly moth eggs.

Naturally, you don’t want to share the veggies you planned on eating with a horde of hungry caterpillars. Additionally, when caterpillars do a great deal of damage to your young plants, they can kill them.

Caterpillars can be a real problem you’re trying to grow your own veggies. They are especially fond of the leafy green vegetables ripening in the autumn. In this article, we will share some smart tips to help you prevent the incursion of moths and caterpillars and keep caterpillars under control.

10 Smart Gardening Practices To Get Caterpillars Under Control

#1 – Don’t light your garden at night. Remember, moths are attracted to light. If you light your garden in the evening, you are sending out a beacon for moths.

#2 – Be observant! Examine your plants on a regular basis: daily is best. Look for moth eggs and caterpillars and remove them as soon as you see them.

If you see any sign of eggs, just snip or pinch off the affected leaves and dispose of them properly. Don’t toss them into your compost heap or you will simply be re-incorporating them into your garden via your compost.

When you examine your plants, carry along a pail of soapy water. Whenever you see a caterpillar, simply pick it off and drop it in the bucket of water. Regular examination and diligent removal can go very far toward keeping your caterpillar population low.

Be advised that a number of caterpillars can sting! This is especially true of furry caterpillars and Puss caterpillars (a.k.a. asps). Be sure to wear protective garden gloves when you are picking caterpillars off your plants.

#3 – Cover your plants with porous netting that will allow air flow and sunlight in while keeping pests off.

#4 – Use smart companion planting to discourage caterpillars. Planting strong smelling herbs such as:

  • Peppermint
  • Lavender
  • Mugwort
  • Sage

Can be very discouraging to caterpillars and a number of other pests.

#5 – Rotate your crops. Don’t plant the same type of plants in the same place year after year. This gives moths and caterpillars a chance to establish themselves. Rotate your crops to keep these pests on their toes!

#6 – Put caterpillars in their place! Of course the caterpillars you most want to get rid of are moth caterpillars. It’s easy to confuse them with butterfly caterpillars, which you want to keep! To avoid accidentally doing away with caterpillars that grow up to become beneficial pollinators, plant a butterfly garden. Set aside a section of your yard or garden for butterfly pleasing plants such as:

Become familiar with the types of butterflies that frequent your area. Learn about the types of flowers that attract butterflies and plant accordingly. Providing butterflies with the plants they desire and their caterpillars with the foliage needed will help prevent having caterpillars gobble up your vegetable garden.

#7 – Make your garden a haven for natural caterpillar predators. Set up bird feeders and birdbaths around your garden to attract caterpillar eating birds.

Attract lizards, box turtles and toads by providing good hiding places (e.g. broken clay pots, logs, etc.). Provide flat rocks for sunning and shallow dishes of water on the ground to keep them happy.

If you have ducks or chickens, allow them the run of the garden from time to time so that they can dramatically reduce your caterpillar population.

#8 – Treat your plants with Bacillus thuringiensis (B. t.). This is a bacterial disease and biological control that only affects caterpillars. It is especially effective when used against very small caterpillars that have only recently hatched. If you see caterpillar eggs on your plants, it’s a good idea to remove them and then treat with B.t. immediately to combat caterpillars emerging from any eggs you may have missed. Read our review on Bacillus thuringiensis (B. t.) here.

B.t. is sold under the brand names Thuricide, Dipel and several others. This product can be dusted over the leaves of the infested plants, or it can sprayed in solution. Be sure to follow packaging instructions to get the correct dosage.

Coat your plants thoroughly so the caterpillars ingest the product when they eat. This organic solution should be used frequently (every 3 to 5 days) until your caterpillar population is under control.

Another, similar product is called Spinosad. This product is made using a bacterium that is commonly found in the soil. Look for it in a number of different organic insecticide products.

#9 – Pyrethrum is a very widely used fairly natural insecticide. The true, organic variety is made using extractions from chrysanthemums flowers. There are also chemical pesticides that are made using man-made forms of pyrethrum. If you see the term “pyrethroids” on the package labeling of a product you are considering using, you will know that is actually a synthetic product.

#10 – Neem oil can also be used to control caterpillars, and it is effective against a number of other garden pests such as beetles and aphids. Take care when using Neem oil. Apply sparingly and only to areas where you have seen moth/caterpillar infestation. It is indiscriminate in its effectiveness and can be harmful to beneficial fauna. Read our review of Neem Oil insecticide here.

amry worm caterpillar chewing away in the garden

Choose Organic Products Whenever Possible

All of the product on this list are organic, so they are not as harmful to beneficial insects has powerful chemical agents. Additionally, they break down fairly quickly and don’t leave harmful residues behind. Still, some (i.e. Pyrethrum and Neem oil) can harm beneficial insects. This is why it’s best to deal with moths and caterpillars manually and through smart partnering with birds and other beneficial garden dwellers.

If you do use an organic pesticide, remember you do will need to use it more frequently than chemical pesticides because these products do break down quickly. Even though they are less harmful to beneficial insects and chemicals, they still do some harm.

Anytime you apply and insecticide for any reason, do so carefully and mindfully. Don’t spray it wholesale or you will end up killing off the good insects that help you.

What To Do about Specific Types of Caterpillars

The types of caterpillars that may plague your garden will vary depending upon where you live. It’s important you learn to identify the caterpillars common to your area. Some types of treatment work well against one type of caterpillars but not against another. Additionally, you’ll want to avoid doing away with caterpillars that are the larvae of beneficial butterflies.

Here are some basic guidelines for common types of caterpillars:

Swallowtail Butterfly Caterpillars:

Don’t kill please! Instead, be sure to mix a few of their favorite greens, herbs veggies into your butterfly garden. These include:

  • Dill
  • Parsley
  • Fennel
  • Carrot Greens
  • Parsnip Greens
  • Queen Anne’s Lace

Swallowtail butterfly caterpillars are large and bright green with yellow and white stripes that run horizontally around the body of the caterpillar. When you find them in an area of your vegetable garden where you don’t want them, simply pick them up and move them to your butterfly garden.

Monarch Butterfly Caterpillars:

If you are fortunate enough to live on the Monarch migration route, take extra steps to welcome these endangered beauties. Be sure to add milkweed to your butterfly garden as it is the only plant their plump, black and yellow striped caterpillar babies will eat.

You can purchase milkweed seed online or from your local garden center. It is available in an interesting array of flower colors and configurations. Planting it in your yard will beautify your yard and help preserve majestic Monarch butterflies.

Cabbage Moth Caterpillars

Row covers provide a good way to protect your brassica (cabbage, broccoli, cauliflower, Brussels sprouts) crops against these hungry caterpillars. You can buy these ready-made covers at your local garden center, or you can make your own.

To do this, you will need to erect a series of hoops over your crop and cover the hoops with a light material that allows good air flow and the passage of sunlight but can still prevent encroachment by moths and caterpillars.

Tomato Horn Worms:

When these caterpillars invade your tomato plants, they can strip them of their leaves in less than 24 hours. Watch for them carefully. They are easy to see because they are quite large.

You can recognize them easily because they have a big spike (horn) on the tail end. The minute you see a tomato hornworm, pick it off and drop it into a bucket of soapy water.

tomato horn worm on a leaf

Asps:

This type of caterpillar is commonly found in shade trees in the southern United States. It is easily distinguished by its furry body. These caterpillars may be gray, tan, yellowish or rust colored. Be very careful to avoid contact with them as they have venomous spines that can inflict a great deal of pain, cause skin rashes and even cause neurological damage.

They are very slow moving and tend to cling tightly to tree bark. It’s best to wear gloves and protective clothing and scrape them off into a pail of soapy water when you see them. Always examine limbs of shade trees before pruning to avoid contact with these caterpillars.

Asps are the pupa of puss moths or flannel moths, which are rather striking in appearance. They are creamy colored with rose highlights on the wings. Their bodies are covered with scales and fur, and their antennae are frilly. If you see them in your trees, you should treat right away with permethrin to prevent them from laying eggs.

Puss moths and asps do not have natural enemies because of their venomous qualities.

Cutworms

These are caterpillars that live under the soil. They eat through the stems of seedlings after dark. You can prevent them from being able to get to the stems by protecting your young seedlings with toilet paper rolls cut to 2 inch lengths. Simply place the section of toilet paper roll around young plants’ stems so that cutworms cannot get to them.

Army Worms

Army worms are black with yellow stripes that run the length of their body. They are a type of caterpillar that always appears en masse or as an “army”. They will eat almost anything, and they’ll eat all of it! Army worms will make short work of large amounts of:

  • Clover
  • Millet
  • Grass
  • Beans
  • Beets
  • Corn
  • Flax

…to name just a few! They will generally eat whatever is in their path. They can be especially destructive to lawns and are very difficult to eradicate from the lawn because they dwell in the thatch.

Sometimes they show up in such large numbers that they blanket the ground, but this is not as common in modern times as it once was. In fact, these days you may not notice them immediately because they hide during the day and eat at night.

If you begin noticing brown patches in your lawn and lots of birds hanging around, it’s an indication that you may have army worms.

Prevent Army Worm Incursion Early

If you have had problems with army worms in the past, there is a test you can perform early in the spring to see if you can expect trouble again. Take a one-gallon can with both ends removed and push one end firmly into the earth. Fill it with soapy water and wait a few minutes.

The soapy water will kill any army worms that may be lurking in that little bit of soil, and they will float to the top. If you unearth half a dozen, you can be pretty sure your soil is badly infested. You should take steps to eradicate the infestation right away.

Luckily, early detection allows you to use less harmful and less invasive means to get your army worm infestation under control.

To deal with this problem in your grass, you should mow the grass very short and water deeply to drive the caterpillars to the surface. Doing this early in the day will enable the birds to help you get rid of them for several hours.

If you’ve caught your army worm problem while the larva are still small, B.t. can be effective against them. If they grow to be a half an inch long or longer, it will not be effective and you may be forced to use a strong, chemical pesticide to deal with them if you have a very severe infestation.

No matter what you apply, be sure to apply it just before dark so that it will have the greatest effect on the caterpillars since they tend to feed overnight. A combination of engaging bird assistance in the morning and applying B.t.(or another product) in the evening should go far to get your army worm problem under control.

After you have applied B.t. or another product to your lawn, don’t water or mow for three days. This will give your application of products a good chance to work.

What To Do About Caterpillars On Bushes And Trees

In the autumn you may see lots of caterpillars on trees, shrubs and bushes. For the most part, they will not harm established plants, and their feasting only lasts a couple of weeks until it’s time for them to go into the pupal stage in preparation for becoming moths and butterflies.

You can use organic pesticides on trees and bushes to control caterpillars; however, this is not usually necessary. You are very likely to receive a lot of voluntary assistance from natural predators in the form of birds, parasitic wasps, spiders and the like in keeping soft, tasty caterpillars under control.

Sometimes, you may see groups of caterpillars all together on one limb munching away. When this is the case, it’s easy to simply cut that limb off and get rid of it, or pick the caterpillars off and drop them into a bucket of soapy water.

Every once in a while, caterpillars appear in huge numbers and can actually strip all of the foliage from trees and bushes. When this happens, you may need to spray with a mild pesticide. Do your best to get rid of as many caterpillars as you can by hand before resorting to potentially hazardous solutions.

Use A Combination Of Methods

Diligence is the #1 deterrent when it comes to caterpillar control. When you keep a close eye on your garden and catch infestations early, you may be able to keep caterpillars completely under control by hand and by engaging the help of friendly fauna and helpful bacteria.

Careful garden planning management and the use of preventative elements such as row covers and strong smelling herbs will also help keep caterpillars at bay. When you turn to these smart, natural solutions quickly and diligently, you may never need to use any kind of pesticide to control caterpillars.

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