What’s Eating My Broccoli? 7 Common Broccoli Pests
Are your broccoli plants covered in tiny holes or suddenly missing part of their delicious crown? Join farmer Briana Yablonski to learn about how to identify and treat some of the most common broccoli pests.
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Broccoli is one of my favorite crops to grow, especially in the cool days of spring and fall. The lush green leaves bring a sense of vitality to the landscape, and the delicious crowns add a hearty element to soups, rice bakes, and stir-fry.
Unfortunately, I’m not the only one who loves broccoli plants. Caterpillars, small beetles, and aphids flock to the plants to devour their foliage and buds. If left untreated, these pests can severely weaken or even kill your broccoli.
Since each pest requires different treatment methods, proper identification is the first step to handling the unwanted diners. I’ll share how to identify common broccoli pests and deal with them, so you can enjoy a bountiful harvest.
Cabbageworms
Cabbageworms are green caterpillars that are the juvenile stage of the small white butterfly known as the cabbage white (Pieris rapae). The caterpillars start small and eventually grow to be about an inch long. Since the adults lay individual eggs rather than clusters, you’ll often see a single cabbageworm feeding on your broccoli leaves.
These wormy pests feed on foliage when the plants are young, but they may move to the broccoli heads when they appear. A single worm can quickly turn a leaf ragged or chew an entire broccoli head, so prompt treatment is crucial to protecting your plants!
How to Treat
One way to control cabbageworms is to exclude the adult butterflies from the plants. If the adults can’t reach your broccoli plants, they won’t be able to lay eggs that turn into the unwanted caterpillars. Covering your plants with row cover or insect netting is the best way to keep the cabbage whites away.
If you don’t want to cover your plants, scout them regularly for cabbageworms. A hole in a leaf means something was munching and demands closer inspection. If you spot one of the green cabbageworms, you can squish it with your fingers or put it into a bucket of soapy water.
While handpicking is often an appropriate control measure for a few plants, it may not be practical if you’re growing a whole row of broccoli plants or other brassicas. Spraying your plants with Bt will kill the cabbageworms without harming other insect families. Make sure to spray the plants every 7-10 days if you notice the caterpillars reappear.
Cabbage Loopers
Cabbage loopers are green worms that are the larval form of a brown owlet moth (Trichoplusia ni). They have noticeable feet and a pale yellow line running down either side of their bodies.
One way to distinguish cabbage loopers from cabbageworms is by observing how the pests move. The loopers arch the middle of their body like inchworms, and the cabbageworms keep their bodies flat as they scuffle forward.
Cabbage loopers feed on broccoli leaves and heads, damaging them in the process. Therefore, you should treat these pests if you notice them on your plants.
How to Treat
Since only the larvae feed on broccoli, excluding the adults from the plants will keep them free from the loopers. Use a piece of row cover or insect netting to cover the plants immediately after you plant them.
You can also control the pests by handpicking them from your plants every one to two days. Another option is to spray the plants with Bt. When the caterpillars ingest the bacteria, they’ll soon die.
Cross-Striped Cabbageworms
Cross-striped cabbageworms also feed on brassicas, but they have a different appearance and growth habit than other cabbageworms. The juvenile forms of the moth Evergestis rimosalis have blueish-gray bodies with black stripes running down the length of their back. Mature caterpillars have yellow sides and orange heads.
The adults lay their eggs in clusters on the undersides of leaves, so groups of larvae often appear and feed at once. The worms feed on broccoli foliage, and large populations can quickly lead to lacy leaves. These pests are particularly dangerous to young, small plants.
How to Treat
You can prevent and treat cross-striped cabbageworms much like other cabbageworms. Covering young plants with floating row cover will prevent the adults from laying eggs on the plants and limit larvae. However, you have to cover plants as soon as you plant them.
If you see the worms on your broccoli plants, you can pick them off or spray your plants with Bt. Although Bt won’t kill the worms immediately, it will stop the worms from feeding and kill them within a few days.
Flea Beetles
These tiny, dark, shiny beetles hop like fleas when disturbed, hence their common name. They feed on a wide variety of crops, but brassicas like broccoli are one of their preferred foods.
Unlike large pests, flea beetles leave many tiny holes in broccoli leaves. While a few of these holes aren’t a problem, large populations can severely weaken young plants and stunt the growth of more mature plants.
Flea beetles generally don’t appear until the weather warms, so you may not notice them in early spring plantings. However, they often arrive in late spring and cause serious damage. Fall broccoli crops are particularly susceptible to flea beetle damage since late summer is often the ideal time for transplanting.
How to Treat
Since flea beetles overwinter in the soil or plant matter, covering broccoli at planting time won’t necessarily exclude the pests. Supporting natural predators is a better preventive measure. Aim to plant a diversity of flowering plants and avoid broad-spectrum insecticides when possible.
Keep an eye out for flea beetles, and treat them when necessary. Although larger broccoli plants can withstand a fair amount of flea beetle damage, small seedlings often require you to treat the pests. Spraying infected plants with pyrethrins or spinosad can help control the beetles.
Harlequin Bugs
Although harlequin bugs (Murgantia histrionica) are beautiful, you don’t want them in your garden. These shield-shaped bugs sport black, white, and orange patterns that make them stand out against green broccoli plants. You may also spot their white and black barrel-shaped eggs on the undersides of leaves.
Both the adults and eggs are cause for concern. The adults and juveniles feed on broccoli leaves, leaving holes in the plants. They’re more common in warm weather, so they’re often a big problem for fall transplants, especially in southern growing areas.
How to Treat
Adults overwinter in debris, so removing old plants from your garden will limit their appearances. However, the bugs can travel, so there’s a good chance they’ll still find their way to your garden. Covering your broccoli plants with row cover will physically exclude the pests and keep your plants safe.
If you spot harlequin bugs on your broccoli plants, you can pick them off and place them into a bucket of soapy water. Another option is to spray the pests with pyrethrin or spinosad.
Aphids
If you’ve spent any time around plants, you’re probably familiar with aphids. These small insects have soft, pear-shaped bodies and unique mouths that are used to drink plant sap. There are hundreds of aphid species that feed on various plants.
Aphids may be green, gray, red, yellow, and numerous other colors. However, green aphids (green peach aphids) and gray aphids (cabbage aphids) are some of the most common aphid species found on broccoli plants.
Although a few aphids won’t cause much damage, these tiny pests can quickly multiply. Large populations can severely weaken young plants, so treating aphids as soon as you spot them is the best way to keep your broccoli healthy.
How to Treat
Natural predators like green lacewings, hoverflies, and parasitic wasps often help keep aphid populations in check. Planting diverse crops and avoiding unnecessary pesticide applications will help keep these good bugs around.
If you notice a few aphids on your plants, you can squish them with your fingers or spray them with soapy water. Larger infestations may require treatment with neem oil, insecticidal soap, or spinosad. However, you should be aware these products may also harm the beneficials that feed on aphids.
Cutworms
If your broccoli seeds have fallen over during the night, cutworms are likely to blame. These worms feed on plant stems near the soil surface, causing seedlings to fall over. There are many cutworm species, but all have smooth bodies that curl into a C-shape when touched.
During the day, the worms typically remain under plant debris or in weeds. They emerge at night to feed on young plants. Since cutworms appear early in the year, they’re typically only problematic for spring broccoli crops.
How to Treat
Since cutworms can kill plants with a single feeding, they’re especially frustrating to manage. If you spot a plant that seems to have been cut, dig around in the soil and organic material near the base of the plant to try to find the worm. Kill any worms you find.
If you’re worried about cutworms, you can use a physical barrier to protect young seedlings from damage. Wrap a piece of aluminum foil around the bottom of the stem while extending the material an inch underground.
