3 Common Kale Pests and How to Manage Them

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Tuscan kale

Growing kale is one of the pleasures of spring vegetable gardening. The sturdy seedlings survive sudden cold spells when given modest protection, so you can get an early start and start harvesting nutritious leaves by the time it’s warm enough to transplant tomatoes. Stately kale plants are pretty, too, so they are a great vegetable to mix with pansies, calendulas or other cool-season flowers as shown in this Garden Planner planting plan for spring kale.

But even easy-to-grow kale has its fair share of insect pests, and because they are so small and furtive, kale pests have special talents for launching sneak attacks. Here I will discuss the three most common kale pests in seasonal order, with links to more information at The Big Bug Hunt, where you can report your sightings.

Cabbage aphids on kale

Cabbage Aphids

In my climate, autumn-grown kale often survives winter and starts growing first thing in spring. Woolly, grey-green cabbage aphids also survive hidden away in tiny crevices. As the plants grow, the cabbage aphids rapidly reproduce in dense colonies, like the one shown above.

Cabbage aphids feed by piercing leaf tissues and sucking out the juices, so a badly colonised kale leaf will never recover and should be pinched off and promptly composted. You can treat small colonies of cabbage aphids with insecticidal soap, but it’s hard to kill every last aphid. Happily, vigorous young plants seem to be of little interest to this kale pest, so you can take out old infested plants and get a new start with your spring crop.

Cabbage White Caterpillars

Cabbage white caterpillars begin appearing in late spring, after you see the adult white butterflies flitting about in your garden. In addition to mating, they are laying eggs on every kale, cabbage, and broccoli plant they can find. This educational video tracks the cabbage white life cycle from egg to butterfly – a drama every vegetable gardener should understand. The small cabbage white is widespread, and in Europe the similar and even more voracious large cabbage white butterfly can leave kale plants badly damaged.

Small cabbage white caterpillars

Many of the caterpillars’ natural enemies, especially wasps, are not yet present in large numbers in spring, so you must protect your plants by hand-picking your cabbage white caterpillars, using polythene or fleece tunnel barriers to prevent egg laying, or using an organic pesticide that uses Bacillus thuringiensis or spinosad as its active ingredient. In very bad caterpillar years I may do all three – hand pick every caterpillar I can find, treat the plants with Bt, and then cover them with lightweight tulle to prevent future egg-laying.

Harlequin Bugs

In North America, harlequin bugs wait until the weather warms in summer to appear on kale plants, and there is no mistaking them because they are so colourful. In my garden, spring-grown kale plants have passed their prime when the harlequin bugs appear, so I take out the plants and compost them rather than fight the bugs. Having the garden become a brassica-free zone for a few weeks in summer deprives all kale pests of the host plants they need, and sets the stage for fewer insects on the fall crop.

Harlequin bugs on kale

In some areas of California and Arizona, the bagrada bug, or African painted bug, has joined the list of serious kale pests. The same pest management approaches that work with harlequin bugs should help with smaller, calico-coloured bagrada bugs, and you may be able to use sweet alyssum as part of your defence. Sweet alyssum is such a strong attractant that the crushed foliage can be used in bagrada bug traps.

With all kale pests, early intervention will make the immediate challenge easier to handle, and often results in fewer pest problems all season long. One of the great things about growing kale is that every season comes with a second chance. After your spring kale become history, you can set out vigorous young seedlings that will mature in autumn’s cooler weather.

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Show Comments


"I have had cabbage worms on my kale the last couple of years. If I plant the kale in a distant garden will they find it in the new location?"
Sarah on Friday 17 March 2017
"Of course they will! They will also fly in from alfalfa or canola fields, or a neighbor's beautiful nasturtiums. Like other butterflies, the cabbage whites use sensory receptors on their feet to discern if they are on a suitable host plant. Kale gets them excited! The planting distance strategy would have an impact on potato beetles or squash bugs, in which the first generation crawls its way to host plants. "
Barbara Pleasant on Saturday 18 March 2017
"I'm growing kale and noticed what looks like a whitish trail on some of the leaves. I have no clue what type of bug did this. Any ideas. "
Gary Heard on Monday 26 June 2017
"I'm growing kale and noticed what looks like a white trail on some of the leaves. I have no clue what type of bug did this. Any ideas. "
Gary Heard on Monday 26 June 2017
"Gary, you are seeing either slug trails or evidence of leaf miners, a fly larvae that feeds inside the leaf in an ingenious tunnel. If the trails wash off, it's slugs or snails. "
Barbara Pleasant on Monday 26 June 2017
"Barbara Pleasant - Thanks of your expert advice. The trail was difficult to remove with a wet rag. "
Gary Heard on Sunday 2 July 2017
"Barbara Pleasant - Thanks for your expert advice. The trail was difficult to remove with a wet rag, but I did. "
Gary Heard on Sunday 2 July 2017
"Hi, just wanting to know the easiest way to get rid of these small grey eggs on the bottom of my kale leaves, THEY ARE EVERYWHERE, keeping them away will be easier now i have read this article, but the ones that are already there"
Brad on Monday 8 January 2018
"I don't know what insect would lay numerous eggs close together on your kale, but a spray of insecticidal soap might be a good idea in case you're seeing aphids and other insect eggs mixed together. "
Barbara Pleasant on Monday 8 January 2018
"I have a worm description that is eating my Kale...this worm is smaller than a cabbage worm, it has a black head, and striped body. This black-headed worm seems to tunnel inside the stems, sometimes I see beige eggs. This worm has a tendency to go for the tiny new leaves turning them a yellowish brown, and also has a bit of Web type material around its hiding places inside the tiny new growing leaves. Do you have ANY IDEA of what it could be? And how to get rid of them?"
Denise DeBoer-Duffer on Friday 2 March 2018
"Hi Denise, If you live in a warm climate, you could be seeing cabbage webworms (Hellula rogatalis). Please check images under that name and see if they match. There are other nocturnal moths so consider if you are in the western US, Spodoptera species like the yellow-striped armyworm could be your culprits. All can be prevented with row covers, or treated with a Bt-based organic pesticide. "
Barbara Pleasant on Sunday 4 March 2018
"Hi am not seeing any worms on my kale but am seeing on nursery the cotyledons have a worm like trail and the leaves turns a bit curl and brownish, how can you help Thank you"
Zara Mohammed on Sunday 20 May 2018
"Zara, pale worm-like trails in leaves are often caused by leaf miners, the larvae of a small fly. The damage is usually slight and passes. Hope this is the cause, and your plants outgrow the problem quickly."
Barbara Pleasant on Monday 21 May 2018
"Hi Barbara, I would appreciate your input on whether you prefer liquid or powdered Bacillus thuringiensis. Today I found a green caterpillar with eggs on one of my Kale plants that I have planted for the first time. I'm a novice gardener and so am just learning as I go. Thanks so much for being here for us! Thanks, Carmy"
carmon moen on Friday 1 June 2018
"A green caterpillar with eggs on its body has been parasitized by a beneficial braconid wasp, so that's a good thing. I prefer liquid BT, but the dust is fine, too. But with only one caterpillar, I would hand pick and not bother with spraying."
Barbara Pleasant on Friday 1 June 2018
"I live on east coast in a coastal region. I planted kale 3 years ago from plants and it lasted until last year when something just ate holes in all the leaves, there was little left. I planted new plants this year and I picked only a few leaves and that something has eaten all the plants leaves and left them sieved with holes all over. I never see anything and see no eggs, but it seems they were waiting for these new plants and never found the others until the the third year. They sustained a bit of cold that we had, but thrived again each year and it warmed up. It was wonderful, until whatever this is has found them. Do you have any ideas and if so, is there anything that I can do to keep them away?"
Betty Saunders on Monday 4 June 2018
"Betty, this sure sounds like night-feeding slugs to me. If it was cabbageworms you would be seeing their trails. If you can't trap them, slug baits that use iron phosphate as their active ingredient are considered safe to use in organic gardens. Good luck! "
Barbara Pleasant on Monday 4 June 2018
"RE: Betty's comment. In a week, the tuscan Kale leaves look like colanders. We found no slugs but many caterpillars, too many to pick and little kale left. How can I send a picture and how can we get rid of the caterpillars"
Lucy on Sunday 5 August 2018
"Lucy, Tuscan kale has the unique ability to regrow from the top when the lower leaves are removed, resulting in a striking architectural plant. I suggest removing and composting all of the tattered leaves and lowest secondary sprouts. Then spray the stalks and tops with a spinosad-based or BT-based organic insecticide every two weeks until early fall, when pest pressure subsides. By then you should have impressive new tops on your plants. "
Barbara Pleasant on Monday 6 August 2018
"My older kale plants have a white powdery substance on the leaves that almost looks like the yeast that forms on grapes. It isn't spotty like mildew but like an even dusting all over, and it rubs/washes off. Is my kale still safe to eat?"
Pam on Sunday 26 August 2018
"Pam, those old leaves probably have developed powdery mildew or another fungal disease. Even though you can wash it off, eating diseased leaves is not generally recommended because of their reduced nutritional value and potential to trigger allergies. That said, we probably eat powdery mildew all the time on cucumbers, summer squash, even tomatoes. Your call! "
Barbara Pleasant on Monday 27 August 2018
"I've had some Kale this year (and last) which has been chopped off almost at ground level, quite cleanly, with some signs of trying to eat the inner parts if the main stalk. The plants are left lying on the ground. I suspect it may be a parrot... Anyone else ever had this problem??"
Andy on Tuesday 21 May 2019
"Yes and then the leaves are being eaten from the outer edges into the stalk of my other plant. No footprints that I can see. I'm thinking maybe a rabbit? But then I would see footprints. Someone mentioned maybe a cutworm. Looked up info on these nasty little creatures and the description of the damage done to my kale matches. Ready to do battle. I like my kale!!! I'm going to try and save it. "
Natalie on Monday 29 July 2019
"Natalie, cutworms normally bother only young seedlings, and cannot seriously harm larger plants. Rabbits are very sneaky, and deer like kale, too! "
Barbara Pleasant on Monday 29 July 2019

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