How to Protect Fall Vegetables From Cabbage Worms and Other Pests

September 5, 2026

How to Protect Fall Vegetables From Cabbage Worms and Other Pests

You planted a beautiful fall garden, came back a few days later, and suddenly your bok choy leaves are full of holes.

What happened?

Just because summer is ending doesn’t mean garden pests are finished eating.

In fact, some of the vegetables we love growing in fall—bok choy, kale, cabbage, broccoli, cauliflower, collard greens, and other brassicas—are also favorites of several garden pests.

I’ve learned that one of the easiest ways to deal with fall garden pests is to protect the plants before they become a problem.

That’s why insect netting has become one of my favorite tools for growing fall vegetables.

If you’re a beginner gardener wondering what’s eating your fall vegetables, here’s how to identify some of the most common pests and protect your plants before they disappear one bite at a time.

Why Are There Holes in My Fall Vegetable Leaves?

Holes in vegetable leaves can have several causes, so don’t immediately assume every hole comes from the same pest.

Some common pests that can damage fall vegetables include:

Cabbage worms
Cabbage loopers
Flea beetles
Slugs and snails
Aphids
Other caterpillars and chewing insects

The type of damage can give you clues about what’s responsible.

Large or irregular holes may point toward caterpillars or slugs.

Lots of tiny holes can indicate flea beetles.

Curled or distorted new growth accompanied by clusters of tiny insects may point toward aphids.

Before treating anything, look closely at the plant and identify the pest whenever possible.

You don’t want to treat a problem you don’t actually have.

What Are Cabbage Worms?

“Cabbage worm” is a common name used for caterpillars that feed on vegetables in the brassica family.

One of the common culprits is the imported cabbageworm, the larval stage of the cabbage white butterfly.

If you’ve ever seen small white butterflies fluttering around your vegetable garden, pay attention to where they’re landing.

The adult butterfly itself isn’t chewing holes in your bok choy.

The problem comes when eggs are laid on susceptible plants and the caterpillars hatch.

Those caterpillars start eating.

And eating.

What Vegetables Do Cabbage Worms Eat?

Cabbage worms are especially interested in vegetables in the brassica family.

That includes crops such as:

Bok choy
Cabbage
Napa cabbage
Kale
Collard greens
Broccoli
Cauliflower
Kohlrabi
Brussels sprouts
Mustard-family crops

This is why growing fall brassicas can sometimes feel like you’re planting a buffet for caterpillars.

Bok choy is one of my favorite fall vegetables, so protecting it from pests is something I take seriously.

What Does Cabbage Worm Damage Look Like?

One of the first signs may simply be holes in the leaves.

As the caterpillars continue feeding, the holes can become larger and more numerous.

You may also notice dark green droppings, called frass, on the leaves or around the center of the plant.

Look closely at the undersides of leaves and along the leaf veins.

The caterpillars can be surprisingly difficult to spot because their green coloring helps them blend into the plant.

Sometimes I notice the damage before I notice the caterpillar.

My Favorite Prevention: Insect Netting

If there’s one thing I want beginner gardeners to remember from this article, it’s this:

Don’t wait for cabbage worms to arrive before protecting your brassicas.

One of my favorite ways to protect fall vegetables is insect netting.

Instead of waiting for caterpillars to damage the plants and then figuring out how to get rid of them, insect netting creates a physical barrier between the plant and the adult insects trying to reach it.

For cabbage worms, that means preventing the adult butterflies or moths from reaching the plants to lay eggs.

No eggs means fewer caterpillars eating your vegetables.

That’s a much easier problem to manage.

Put the Insect Netting on Early

Timing matters.

Ideally, put insect netting over your susceptible vegetables as soon as you plant them.

If you wait until the leaves are already full of caterpillars and then cover the bed, you can accidentally trap the pests underneath the netting with their favorite food.

Before covering established plants, inspect them carefully.

Check:

The tops of leaves
The undersides of leaves
New growth
The center of the plant
Leaf stems
Around the base of the plant

Remove any caterpillars or suspicious eggs you find before installing the netting.

Make Sure There Are No Gaps

Your insect netting only works as well as your installation.

If butterflies and moths can crawl or fly underneath it, they can still reach your plants.

I use supports or hoops to hold netting over my garden beds and make sure the edges are secured.

You can use garden clips, landscape staples, boards, rocks, or another suitable method to keep the edges closed.

The exact setup doesn’t matter as much as the basic principle:

Don’t leave an easy entrance.

Check the netting periodically because wind, harvesting, watering, or garden maintenance can create gaps.

Should Insect Netting Touch the Plants?

When possible, I prefer supporting the netting above the plants rather than simply laying it directly on top of them.

Hoops or another support system give the vegetables room to grow and make it easier to keep the cover in place.

It also prevents the netting from weighing down tender seedlings.

Remember to give your plants enough vertical and horizontal room underneath the cover.

That tiny kale transplant may not stay tiny for long.

Do You Have to Remove Insect Netting for Pollination?

For the leafy brassicas you’re growing for their leaves or heads—such as bok choy, cabbage, kale, collards, broccoli, and cauliflower—you generally don’t need pollinating insects to produce the part you’re planning to eat.

That makes insect netting especially useful for these crops.

This is different from crops such as squash, cucumbers, and melons that depend on pollination to produce fruit.

If you’re growing brassicas specifically for seed production, that’s another situation because eventually flowering and pollination become important.

But for a typical fall vegetable crop, you can keep your brassicas protected.

What If I Already Have Cabbage Worms?

Don’t panic.

A few holes don’t mean the entire plant is ruined.

Start by inspecting the plant carefully.

Turn over every leaf and look for caterpillars and eggs.

If you only have a few plants, hand-picking can be one of the simplest solutions.

Remove the caterpillars and dispose of them.

Then continue checking the plants regularly because you may have missed eggs or tiny caterpillars.

Once you’re confident the plants are clean, you can protect them with insect netting to reduce the chance of another infestation.

What About Bt for Cabbage Worms?

Another option gardeners may encounter is Bt, short for Bacillus thuringiensis.

Certain Bt products are labeled for controlling specific caterpillar pests.

When a caterpillar consumes the appropriate Bt strain, it can stop feeding and die.

However, Bt isn’t something I would spray automatically just because I see holes.

First identify what’s eating the plant.

Bt products for caterpillars don’t solve every garden pest problem.

If you choose to use one, make sure the product is labeled for the specific crop and pest you’re treating, and always follow the label instructions.

Remember that caterpillars aren’t automatically “bad.” Butterflies and moths are part of the ecosystem, and Bt can affect susceptible caterpillars that consume treated plant material.

Use targeted pest control rather than spraying unnecessarily.

Flea Beetles: Tiny Holes Everywhere

If your brassica leaves look like someone fired a tiny shotgun at them, flea beetles may be responsible.

Flea beetles are small beetles that chew numerous tiny holes in leaves.

Young seedlings can be particularly vulnerable because they don’t have much leaf area to spare.

A mature plant may tolerate some feeding.

A tiny seedling can quickly become overwhelmed.

This is another reason I like protecting young plants early.

Insect netting or an appropriate row cover can help prevent flea beetles from reaching plants, provided they’re not already underneath the cover.

Slugs Can Be a Big Problem Too

Slugs are another pest I’ve dealt with in my garden.

Unlike cabbage worms, insect netting isn’t going to solve a slug problem because slugs come from the soil and surrounding garden rather than flying in from above.

Slugs often feed at night or during cool, damp conditions.

Their damage can include irregular holes and chewed leaf edges.

You may also notice slime trails.

If you suspect slugs, go outside in the evening or early morning and inspect the plants.

Sometimes that’s the easiest way to catch the culprit.

How I Reduce Slug Problems

Start by making the environment around vulnerable seedlings less inviting.

Remove unnecessary hiding places near the plants, including piles of decaying plant material where slugs can shelter.

Avoid keeping the soil constantly soggy.

That doesn’t mean letting your vegetables dry out. Fall seedlings still need adequate moisture.

The goal is simply to avoid creating persistently wet conditions unnecessarily.

You can also hand-pick slugs when you find them.

If you use a commercial slug-control product, choose one labeled for use around edible vegetables and follow the label exactly.

Aphids on Fall Vegetables

Aphids can also show up on fall vegetables.

They’re tiny, soft-bodied insects that often gather in clusters, especially on tender new growth and the undersides of leaves.

Instead of chewing large holes, aphids suck plant sap.

Heavy infestations can cause distorted growth, curled leaves, or weakened plants.

If you find a small number, sometimes a strong stream of water is enough to knock them from sturdy plants.

Continue checking afterward because one treatment may not solve the entire problem.

Beneficial insects such as lady beetles and lacewings also feed on aphids.

That’s another reason I don’t want to reach for a broad-spectrum insecticide every time I see an insect in the garden.

Some insects are helping us.

Not Every Bug Is a Pest

This is an important lesson for beginner gardeners.

Seeing an insect on your vegetable plant doesn’t automatically mean you need to kill it.

Gardens are ecosystems.

You’ll find pollinators, predators, decomposers, and insects that simply happen to be passing through.

Before treating your garden, ask:

What insect is this?

Is it actually damaging my plant?

How much damage is occurring?

Is the plant healthy enough to tolerate some damage?

Is there a simple physical solution first?

Learning to identify what’s happening in the garden can save you from unnecessary treatments.

Check Your Fall Garden Regularly

One of the easiest pest-control methods doesn’t require buying anything.

Walk through your garden.

I know that sounds overly simple, but catching a pest problem early can make an enormous difference.

Look at your plants every few days.

Don’t just look at them from several feet away.

Get close.

Turn over the leaves.

Look at the new growth.

Check the center of your bok choy.

Look underneath your kale.

Search for:

Holes
Caterpillars
Eggs
Frass
Tiny beetles
Aphid clusters
Slime trails
Wilted seedlings
Chewed stems

A problem that’s easy to handle today can become much harder after another week of feeding.

Healthy Plants Can Handle Some Damage

Here’s something else I think beginner gardeners need to hear:

Your vegetable leaves don’t have to look perfect.

A few holes aren’t necessarily a disaster.

We grow these plants outside.

Something is probably going to nibble on them eventually.

The goal isn’t to produce flawless plants for a photo.

The goal is to keep pest pressure low enough that your vegetables can continue growing and produce something you can harvest.

If my bok choy has a few holes but is otherwise healthy and growing well, I’m not going to panic.

But if I see the damage increasing rapidly, that’s when I investigate.

Remove Badly Damaged or Diseased Leaves Carefully

If a leaf is severely damaged, dying, or diseased, removing it may sometimes make sense.

But don’t strip a plant of healthy leaves just because they have cosmetic holes.

The leaves are still producing energy for the plant.

A slightly chewed kale leaf can still do its job.

And depending on the type and extent of damage, it may still be perfectly usable in the kitchen after being thoroughly washed and inspected.

Keep the Garden Clean, But Don’t Obsess Over It

Removing dead or heavily diseased plant material can eliminate some hiding places for pests and help keep your growing area manageable.

But garden cleanup doesn’t mean your soil needs to be bare and sterile.

Organic matter and living organisms are important parts of healthy soil.

The goal is simply to pay attention to material that may be harboring a known pest or disease problem.

Rotate Crops When You Can

Crop rotation can be useful for reducing certain recurring pest and disease problems.

Instead of planting the same crop family in exactly the same location year after year, move it when practical.

However, I garden in a small space.

Perfect crop rotation isn’t always realistic.

And I think that’s worth saying.

If you only have a few raised beds or containers, you may not have enough room to follow an elaborate rotation system.

Do what you reasonably can and combine it with other strategies such as pest monitoring, sanitation, insect barriers, and healthy soil.

My Simple Fall Pest-Protection Routine

I prefer to keep pest management relatively simple.

When I plant bok choy, kale, collards, cabbage, or other brassicas, I try to:

Inspect seedlings before planting.
Plant into healthy, prepared soil.
Cover susceptible crops with insect netting early.
Secure the edges so pests can’t easily get underneath.
Check the plants regularly, including underneath the leaves.
Hand-pick caterpillars or other pests when practical.
Identify the pest before using any treatment.
Use targeted controls only when they’re actually needed.

Prevention doesn’t mean you’ll never see a pest.

It simply gives your vegetables a better chance.

Protect the Plant Before the Damage Starts

One of the biggest changes I’ve made as I’ve gained gardening experience is becoming more proactive.

As a beginner, it’s easy to wait until something goes wrong.

You see holes.

Then you search for the pest.

Then you try to figure out what to do.

But once you know that cabbage butterflies visit your garden every year, you can plan for them.

Once you know slugs love your leafy greens, you can start checking early.

Once you know flea beetles attack tiny brassica seedlings, you can protect those seedlings from the beginning.

That’s the difference between reacting and preventing.

You Don’t Need a Pest-Free Garden

A successful garden isn’t a garden without insects.

That’s probably impossible—and it wouldn’t necessarily be desirable.

Instead, I want a garden where my vegetables can grow alongside everything else without being completely destroyed.

Sometimes that means accepting a few holes.

Sometimes it means picking a caterpillar off my bok choy.

And sometimes it means putting insect netting over an entire bed before the cabbage butterflies even get the opportunity.

For my fall brassicas, prevention is usually much easier than trying to rescue badly damaged plants later.

So if you’re planting bok choy, kale, cabbage, collards, broccoli, cauliflower, or other brassicas this fall, don’t wait until the leaves look like Swiss cheese.

Protect them early, check them often, and learn which insects are actually visiting your garden.

That’s one more skill that will help you confidently grow food at home.

Let’s grow food at home.

Frequently Asked Questions

What is eating holes in my bok choy?

Several pests can create holes in bok choy leaves, including cabbage worms, flea beetles, slugs, and other chewing insects. Look closely at the size and pattern of the damage, inspect underneath the leaves, and look for caterpillars, frass, tiny beetles, or slime trails before deciding how to treat the plant.

How do I keep cabbage worms off my vegetables?

A physical barrier such as insect netting can prevent adult cabbage butterflies and moths from reaching susceptible crops and laying eggs. Install it early, secure the edges, and make sure pests aren’t already underneath the cover.

What vegetables should I protect from cabbage worms?

Pay particular attention to brassicas such as bok choy, cabbage, Napa cabbage, kale, collard greens, broccoli, cauliflower, kohlrabi, and Brussels sprouts.

Can I leave insect netting over my vegetables all fall?

For leafy and heading brassicas being grown for food rather than seed, insect netting can generally remain in place as long as the plants have enough room, airflow isn’t excessively restricted, and the cover remains properly secured. Open it when necessary for harvesting, weeding, or maintenance, then close it again.

Do cabbage worms disappear when fall arrives?

Don’t assume pest pressure ends just because temperatures begin cooling. Continue inspecting your plants throughout the fall growing season.

Are vegetables with insect holes safe to eat?

Minor insect feeding doesn’t automatically make a vegetable unusable. Inspect the crop carefully, remove damaged areas if necessary, and wash produce thoroughly before eating it. Discard vegetables that are rotten, badly contaminated, or otherwise unsafe to eat.