Broccoli is one of the most popular cruciferous vegetables in the country. When I was a child, we loved it because each piece of broccoli looked like a tiny tree. We could eat our broccoli pretending to be dinosaurs or giraffes. It was magical.
These days, I’m growing rows of broccoli to feed my little dinosaurs all summer and through the fall. Broccoli is a straightforward, easy-to-grow vegetable that can produce harvestable stalks in a relatively short growing season.
As with all vegetables, broccoli plants come with their own set of pests and diseases. As part of the cabbage family, you’ll find your broccoli plants plagued by similar issues. Let’s start with broccoli pests.
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Broccoli Pests
This list could be pretty long, but we’re going to discuss just the most common broccoli pests that you might encounter.
Insects are the pests we’ll be talking about the most here. But remember that one of the biggest and most common pests to a broccoli patch is Peter Cottontail.
1. Rabbits
Rabbits can wipe out your entire batch of broccoli in one night. They love it. When it comes to broccoli pests, few others can destroy your plants as rapidly.
I once lost three separate broccoli plantings to one intrepid bunny.
If you think rabbits might have a chance to steal your broccoli, act defensively immediately. Good fencing, sulfur deterrent sprays, and predator scent sprays are effective. I’ve successfully used all of them.
But the best protection is a big dog that spends much of his time near your garden. Then, his scent is layered over and over again in the area, and the poor rabbits go looking elsewhere for a meal.
Find the best rabbit repellent for your garden in our guide.
2. Flea Beetles
The crucifer flea beetle (Phyllotreta cruciferae) leaves a trademark “shothole” effect on the leaves of your plants that looks like someone shot up your leaves with a BB gun. These tiny, shiny beetles gnaw through leaves and jump away like fleas when you frighten them.
Usually, flea beetles can’t do terminal damage to establish plants, but they can make the plants weaker and more susceptible to disease. They can also wipe out seedlings and young plants. Flea beetles may be small, but when it comes to broccoli pests, they’re one of the most prolific.
Flea beetles tend to overwinter on garden debris. Prevention is the best cure, so clean up your garden well in the fall and rotate your crops to avoid giving this pest easy access to more cruciferous plants.
Row covers can help protect young plants, as well. If you notice an infestation, neem oil is effective when applied as a spray.
3. White Cabbageworm
Oh, the cabbageworm! These little monsters worm their way into so many brassica gardens. Large and small, cabbage white or cabbage worms (Pieris rapae) are a huge problem. The worm itself isn’t white; the adult butterfly is. It’s also not a worm but a caterpillar.
When these greedy, green broccoli pests transform, they become pretty, white butterflies. The butterflies don’t eat brassicas. But their larvae do.
Protect your broccoli if you see white cabbage butterflies brightening up your yard! The long, green cabbage worms will chew large holes in the leaves. Fortunately, these pests are slow-moving, sluggish creatures. They can’t dart away from you.
Pick them off one by one and squash them or feed them to your chickens. Head to our guide to learn 10 ways to deal with cabbageworms.
4. Diamondback Moth
Unlike the pretty white butterflies that leave greedy cabbage worms in their wake, Diamondback moths (Plutella xylostella) are not a sweet, attractive addition to the garden.
When not in flight, the adults look like a cross between a snake and a praying mantis. Their children are larvae that look brown and knobbly until they start to feed on broccoli leaves. As they eat, the larvae turn a soft green, like cabbageworms.
They tend to feed on the underside of leaves. So, if you see ragged, larger holes in your leaves and no sign of cabbageworms, turn it over and pluck off the diamondback moth larvae lurking beneath.
These aren’t the most common broccoli pests, depending on where you live. So assume cabbageworms unless you see evidence otherwise.
These larvae are very small, however. If you don’t see them, try spraying with insecticidal soap or wiping the underside of the leaf with a soft cloth soaked in neem solution.
Learn more about diamondback moths in our guide.
5. Thrips
There are a variety of thrip species in the world. Almost all of them will cheerfully feed on broccoli if they get the chance. Thrips are tiny, almost invisible without a magnifying glass, voracious insects with a thirst for brassica juice.
They bite and suck out the life’s blood of your plants using their sucking mouthparts, transmitting diseases as they go. In fact, it’s that last part that makes thrips such problematic broccoli pests.
Essentially, thrips are the ticks of the plant world. Applications of insecticidal soap can also help in controlling a thrip invasion.
Avoid planting your broccoli near onions to deter thrips because the two plants share thrip species. Onion thrips (Thrips tabaci) and western flower thrips (Frankliniella occidentalis) feed on brassicas and alliums.
Broccoli Diseases
Most human diseases are either viral or bacterial. Most plant diseases are fungal or bacterial. But sometimes, a fungal disease can lead to a viral one. Sometimes fungi make it easier for viruses or bacteria to take hold.
Diseases and their causes aren’t always as straightforward as we might want them to be. Unlike broccoli pests, they can be hard to identify. But, armed with a basic understanding, we can do a lot to help our plants thrive.
Like most vegetables, broccoli plants are susceptible to rust, dampening off, and Alternaria leaf spot. But as brassicas, they have other diseases that target them specifically.
1. Clubroot
The pathogen that causes this disease (Plasmodiophora brassicae) is specific to brassicas. Clubroot is a fungal disease that attacks the plant’s roots. Broccoli plants with clubroot will yellow and wilt during the day while perking back up at night.
Infected plants grow slowly and remain stunted throughout their lives. When dug up, you’ll see the roots are swollen and distorted.
Once clubroot is in the soil, it’s tough to get rid of. The fungus that causes clubroot can live for years in soil. Moving your plants to a totally different location can help. So can applications of lime to the soil.
Plant clubroot-resistant cultivars and actively work to reduce the spread of clubroot by keeping your soil clean and using only certified transplants from reputable nurseries. Learn more tips in our guide.
2. Downy Mildew
Downy mildew is a common disease for many species of plants. Broccoli is especially susceptible to it. Maybe because they require consistently moist soil, and the pathogen that causes downy mildew spreads readily in damp soil.
In brassicas, downy mildew is caused by the oomycete Hyaloperonospora parasitica. An oomycete is a water-based mold closely related to algae.
When your plants have an infection, you’ll see small lesions on the leaves that gradually expand into yellow or orange necrotic patches. The underside of the leaf will be coated in fluffy, mildewy, white growth.
Remove all affected leaves to control this disease. Then, treat the plants with a fungicide that contains copper like Bonide’s Captain Jack. Mancozeb and Revitalize also work. It helps to rotate products because the disease can become resistant.
If your garden tends toward dampness, try to keep downy mildew at bay by remove all garden debris like rotting leaves and turning soil over in the fall.
3. Black Rot
This bacterial disease causes characteristic, v-shaped lesions in the leaf margins. The lesions eventually grow together, making the whole leaf look scorched and withered.
Black rot (Xanthomonas campestris pv. campestris) is incredibly hard to get rid of once it’s made a home for itself in your garden. The best way is to solarize the soil two or three years in a row without growing anything on the plot during that time.
To keep black rot from making your broccoli bed a wasteland, rotate between cruciferous and non-cruciferous vegetables every two years and keep your garden clean and clear of weeds and debris as much as possible.
4. Fusarium Yellows
Fusarium yellows sound like an indie band, but it’s actually another pathogen looking to kill your brassicas. This fungal disease thrives when cruciferous vegetables are growing in hotter temperatures.
Fusarium yellows (Fusarium oxysporum f. sp. conglutinans) affects cabbage and occasionally broccoli grown primarily in temperatures between 75-85°F. So, if you’re growing broccoli in the summer, watch out.j
Fusarium yellows will cause about half your plant to turn a sickly yellowish color. If the temperatures don’t cool off quickly, the whole plant could end up stunted and weak. With an advanced disease, your broccoli will never develop a head.
There’s no cure for the fusarium yellows, unfortunately. Like so many fungal diseases, rotate your crops regularly and keep a clean garden to keep the disease at bay.
Preventing Problems
The best way to keep your broccoli plants safe from pests and diseases is by carefully selecting and preparing the garden bed. Broccoli plants like sunny spots, cool (but not cold) temperatures, and moist, fertile soil.
Since broccoli plants have a short root system, they need consistent want and plenty of rich soil right near the base of the plant.
In hot weather, during the middle of summer, broccoli does better in partial shade, where it can cool off during the hottest times. Extra watering is essential to keep the plant from bolting if you’re growing broccoli in hot summer weather.
If you’re new to growing broccoli but have grown other brassicas, plant your broccoli in a new bed that hasn’t been used within the past two years to grow cabbages, arugula, or other brassicas.
Broccoli is a hardy plant. It grows best in cool weather – mid-late spring and early fall are its favorite seasons. In scorching weather, broccoli will sometimes struggle with early bolting.
The stalk of broccoli – that looks like a little tree – which we harvest and eat is the immature flowerhead of the plant. Once it blooms though, broccoli gives off that unpleasant, old-cabbage scent and tends to taste bitter. The top portion of the stalk is edible and is fantastic in stir-fries.
