Common Broccoli Pests and How to Control Them

Broccoli is a satisfying plant to grow.

While zucchini is prolific and leafy greens don’t take much effort, broccoli makes you work for it.

But when you get it right, you’re rewarded with big, beautiful heads that taste all the better for having grown them yourself.

I think that’s why it can be extra frustrating when things go wrong. And when broccoli pests are invading your garden, things can go terribly, terribly wrong.

A close up vertical image of a broccoli plant showing damage by pests. To the top and bottom of the frame is green and white printed text.

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This year, arm yourself against these marauding menaces with the knowledge of what to look for, how to prevent them from attacking, and what to do if you find pests on your plants.

Coming up, we’ll discuss these common culprits:

Pests are a part of every gardener’s life, but you don’t have to let them win. Let’s jump in!

1. Aphids

Dealing with aphids is frustrating because they’re so common. Plus, they can spread disease. But on the bright side, they’re also fairly easy to deal with.

A close up vertical image of a broccoli plant infested with cabbage aphids pictured on a soft focus background.

Broccoli plants are commonly infested by cabbage (Brevicoryne brassicae) and turnip aphids (Lipaphis erysimi), in particular.

Don’t worry too much about which type you’ve got.

All aphids are treated the same way. Head to our guide to dealing with aphids to learn more and to figure out how to rid your garden of them.

2. Cabbage Loopers

Cabbage loopers (Trichoplusia ni) are inch-long green caterpillars. They’re common across the US and they love to munch on brassicas.

Plus, they’re voracious and they can rapidly leave your plant looking more like green Swiss cheese than a veggie you’d like to eat.

A close up horizontal image of a cabbage looper inching its way along a leaf, creating damage in its wake.

They don’t stop at the foliage, either. The worms can burrow into the heads of your broccoli. That’s not a surprise you want to find when you’re prepping your harvest in the kitchen.

To learn more about these common pests, check out our comprehensive guide to cabbage loopers, which can help you learn how to identify and banish them.

3. Cabbage Root Maggots

Cabbage root maggots (Delia radicum) don’t look like much. The adults resemble small house flies, and the larvae are grub-like maggots that grow to about a third of an inch long.

But don’t let that fool you. Despite their unimpressive appearance, they can do quite a lot of damage.

A close up vertical image of cabbage fly larva aka cabbage root fly in the soil.

The larvae attack the plant’s roots, and you won’t usually know you have an infestation until the damage is done. That makes prevention and the ability to spot these pests early on essential.

Fortunately for us (and unfortunately for cabbage maggots), our guide will help you become an expert in dealing with them.

4. Cabbage Webworms

Cabbage webworms (Hellula rogatalis) are common in the southern half of the US, though there have been reports of them as far north as Nova Scotia, Canada.

These half-inch brown and tan worms have a black cap on their heads, and they can totally destroy your harvest.

They emerge in groups of hundreds to feed on plant buds and leaves, but it only takes two to destroy a plant significantly enough to ruin your broccoli harvest.

A close up horizontal image of the larvae of a cabbage webworm on a white background.

They can bore into the buds, which kills them. If this happens, you might see a few subsequent lateral buds develop, but they usually won’t grow large enough to eat or they’ll be distorted. That means no broccoli for you!

They also fold leaves and spin webs all over foliage, which stunts the plant’s growth. In large enough numbers, they can even kill an entire plant.

They’re active in the fall, so if you’re growing your broccoli in the spring, you’re home-free.

Everyone else, though… well, you’ll have to be on the alert.

The Old World cabbage webworm (Hellula undali) is often confused with the common cabbage webworm. They do similar damage, look similar, and may be controlled in the same way.

The main difference is that they appear in a wider range of areas, from Hawaii to Asia.

Fortunately – since they’re so destructive – there are lots of ways to control either of these webworm species. Handpick them when you spot them and drown them in soapy water.

You should also encourage beneficial predators to visit your garden, like birds, ladybugs, and yellowjackets.

Products that contain Bacillus thuringiensis subsp. kurstaki such as Monterey Bt Liquid are effective, particularly if you apply them right as the worms emerge.

A close up square image of two bottles of Monterey Bt Ready to Use isolated on a white background.

Monterey Bt Liquid

Arbico Organics carries it in 32-ounce ready-to-use and hose-end containers.

Insecticidal soap also works, so long as you keep reapplying it every seven days or so when the pests are present.

A close up vertical image of a spray bottle of Bonide Insecticidal Soap isolated on a white background.

Bonide Insecticidal Soap

I use Bonide’s Insecticidal Soap, which is also available at Arbico Organics. They sell it in quart-sized ready-to-use bottles.

5. Cabbage Worms

You’d think from the name that cabbage worms would stick to feasting on cabbages, but any type of brassica is at risk of infestation by these larvae.

There are several types of cabbage worms to keep an eye out for: the large cabbage white or imported cabbage worm (Pieris rapae), the southern cabbage worm (Pontia protodice), the mustard white (Pieris napi), and the cross-striped cabbage worm (Evergestis rimosalis).

A close up vertical image of a cabbage white butterfly caterpillar on a leaf.

The cross-striped cabbage worm is bluish-gray with black horizontal stripes, and a single yellow stripe on each side.

Cabbage whites are green with a pale yellow stripe, while southern cabbage worms are green with multiple bright yellow stripes that extend over the length of their bodies.

Mustard whites have a dashed yellow line down their sides.

They will all chew holes in the leaves of your broccoli, which can stunt or even kill the plant if they appear in large enough numbers.

A close up horizontal image of a broccoli plant with extensive damage from pests that has been almost completely defoliated.

Handpicking any caterpillars you see is always a good idea. You should also do your best to encourage predators like birds, yellowjackets, and ladybugs to come to your garden.

If you don’t have lots of ladybugs in your garden naturally, you can purchase them at a local nursery or online.

Be sure to look for ones that have been raised in captivity rather than ladybugs collected from the wild and shipped elsewhere.

You can also use the same products on these pests that you would use to control cabbage webworms.

6. Cutworms

Cutworms are the larvae of certain species of moths from the Noctuidae family. These pests chew through the base of young broccoli plants, cutting them off and killing them.

A close up horizontal image of a cutworm on a green leaf.

If you come outside one morning and find your seedlings dead on the ground and severed at the base, you can be pretty confident that you’ve got some of these wrigglers in your garden.

Read our comprehensive guide on identifying, preventing, and controlling cutworms for more information.

7. Diamondback Moth Caterpillars

In case you haven’t noticed yet, one of the most common varieties of pests you’ll face are caterpillars of all kinds. Diamondback moth caterpillars (Plutella xylostella) are yet another species that may plague your crop.

A close up horizontal image of a caterpillar on a leaf pictured on a soft focus background.

These creepy-crawlies are about a third of an inch long, and light green with small black hairs. They’re pointed on both ends, which helps to differentiate them from other types of caterpillars.

Another way to identify them is to disturb them; they’ll drop down on a silken thread to try to escape.

Treat them as you would cabbage worms or cabbage webworms.

8. Flea Beetles

Crucifer flea beetles (Phyllotreta cruciferae) are tiny beetles that hop around from plant to plant, nibbling little holes in the foliage.

They don’t typically cause as much damage to broccoli as they do to other crucifers, thanks to the waxy coating that covers the leaves. Usually, they’ll just feed on the margins of the foliage and don’t cause any serious damage.

A close up horizontal image of a crucifer flea beetle on a leaf in high magnification pictured on a soft focus background.

If the damage ended there, you could safely just ignore them. But they can also spread disease, so you should address an infestation before it causes more problems.

Even better, plan ahead to avoid having flea beetles visit your veggie patch in the first place.

Crop rotation, removing debris from the garden in the fall, and keeping weeds out throughout the season will go a long way towards discouraging these annoying pests.

Row covers are another excellent option. They prevent the beetles from landing on your crops in the first place.

It’s also a good idea to separate broccoli plants from each other with other non-cruciferous plants. This makes it more challenging for the beetles to find their favorite foods.

Anise, dill, chamomile, marigold, and clover are good options for companion planting, since they attract insects like damselbugs and lacewings, which are flea beetle predators.

Learn more about how to control flea beetles in our guide.

9. Harlequin Bugs

Harlequin bugs (Murgantia histrionica) are a common pest in the southern half of the US, where they can cause serious financial losses by destroying commercial crucifer crops.

They can quickly ruin your home harvest too if you don’t keep them in check.

They feed on plants by piercing them and sucking out the sap. As they feed, the broccoli plants start to wilt and turn yellow or brown. Eventually, the plants may die.

The bugs have black and red or yellow spotted bodies with flat, shield-like shells. When mature, they are about a third of an inch long.

A close up vertical image of a harlequin bug on the leaf of a plant pictured on a soft focus background.

Your first line of attack should be to grab any harlequin bug that you see in your garden and drown it in soapy water. 

As with the caterpillars on this list, encouraging predators like birds and ladybugs to visit can help, as can keeping your garden well-weeded.

Failing that, an insecticide that contains pyrethrins such as Monterey Bug Buster can be effective.

A close up vertical image of a bottle of Monterey Bug Buster-O isolated on a white background.

Monterey Bug Buster

Arbico Organics carries eight- and 12-ounce containers of this broad insecticide.

Spray your plants as soon as you note the presence of these beetles. Don’t use it for more than two years in a row, however, or you risk fostering resistance.

10. Root-Knot Nematodes

Root-knot nematodes (Meloidogyne spp.) are known to attack a massive range of plants, including broccoli and other cole crops.

These microscopic nematodes live in the soil and feed roots, causing knots and bumps to form in the roots and reducing the plant’s vigor.

A close up horizontal image of a root of a plant displaying damage from root-knot nematodes.

Above ground, it can be hard to tell if you’re dealing with this pest, since your plants will generally just look stunted or wilted.

You might also see some yellowing of the leaves. As you probably noted, all of these symptoms are pretty generic and common.

You can pull the plants to confirm the presence of nematodes. Look at the roots and examine them for galling.

Otherwise, you can send a soil sample to your local extension office for testing. Once your plant is infected, there is no cure.

Be absolutely sure to rotate your crops if you have an infestation of nematodes. Don’t plant anything in the same spot for at least four years.

You should also remove any weeds, since nematodes can survive on many different weed hosts.

You should also treat the soil with a nematicide.

A close up vertical image of a bottle of Monterey Nematode Control isolated on a white background.

Monterey Nematode Control

There are many out there, so check with your local nursery for recommendations. Or, head over to Arbico Organics to grab a quart of Monterey Nematode Control, which may be applied as a soil soak.

You can learn more about root-knot nematodes in our guide.

11. Thrips

There are three kinds of thrips out there that are just waiting to get their sucking mouthparts into your broccoli plants: Western flower thrips (Frankliniella occidentalis), corn thrips (F. williamsi), and onion thrips (Thrips tabaci).

None of these prefer broccoli over their favorite foods, which are onions, garlic, corn, grains, nightshades, leafy greens, and cabbage. But they won’t turn down a broccoli meal if it’s on offer.

A close up vertical image of a potato thrip on a green leaf in high magnification.

Thrips are small, usually about a third of an inch in length. Adults have wings, while the immature insects don’t. They can range in color from light yellow to dark brown. And they can produce up to eight generations per year.

While their feeding can cause some unwelcome symptoms, such as stippling and even stunting, the real danger is that they can spread disease, most notably mosaic virus.

On the bright side, they devour spider mites, so they’re not all bad. However, if you don’t have spider mites on your plants, they’ll start eating the plants instead.

Whether to treat a thrips infestation or not is a personal decision. Some gardeners opt to leave them alone, since they won’t usually do enough damage to prevent you from growing big, bountiful broccoli heads.

Plus, once they’ve infested your plants, they’ve probably already spread any diseases that they’re carrying, so it’s too late.

On the other hand, you can’t be too careful. If you decide to treat, insecticides containing spinosad, permethrin, or pyrethrins are effective, as is insecticidal soap.

Make your garden less appealing to these pests by introducing or encouraging minute pirate bugs, which are a natural predator. Keep weeds under control to deny thrips a place to hide.

Learn more about how to battle an infestation of thrips in our guide.

Beat Back Broccoli Pests

Looking at this list, you might think the battle against broccoli pests is futile. But a little bit of prevention goes a long way towards discouraging most of these pests.

Crop rotation, regular weeding, and encouraging beneficial insects and birds to come to your garden will make all the difference.

A close up horizontal image of two hands holding a broccoli leaf that is displaying pest damage.

If you need a refresher on how to grow and care for broccoli in your garden, check out our guide.

Have you ever dealt with broccoli pests? Which ones did you encounter? And what method did you find effective for dealing with them? Let us know in the comments below.

After you’ve won your bug battle, you might want to explore some of our other broccoli guides next, including:

About Kristine Lofgren

Kristine Lofgren is a writer, photographer, reader, and gardening lover from outside Portland, Oregon. She was raised in the Utah desert, and made her way to the rainforests of the Pacific Northwest with her husband and two dogs in 2018. Her passion is focused these days on growing ornamental edibles, and foraging for food in the urban and suburban landscape.

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