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Learn about organic pest control for your kale and brassica plants if you’re tired of your insects getting more food from your garden than you do.
Last updated: May 6, 2019
Our edible organic landscape is a brassica-producing machine for 3 out of 4 seasons of the year (our summers are too hot to grow brassicas).
In case you don’t know, brassicas are a genus of plant that produce a huge number of the veggies you see on your dinner table: kale, cabbage, Brussels sprouts, kohlrabi, broccoli, turnips, radishes, rutabagas, bok choy, turnips, mustards, and more.
It’s hard for us to imagine how sad and dreary the world would be without brassica veggies. Whether it’s huge salads made from fresh kale, stir fries made of kohlrabi and broccoli, or sauerkraut made from cabbage and radishes, brassicas are a staple veggie in our culinary repertoire.
Organic Pest Control For Your Kale and Other Brassicas
As it turns out, people aren’t the only ones who love brassica veggies. Depending on what region you live in, there’s a good chance that you have species of pest insects that will want to share your brassicas with you.
The good news is that we guarantee there are things you can do to deal with your brassica pests using safe, organic methods that reduce/eliminate broader environmental impacts without harming other non-target insects like bees and butterflies.
Let’s start with the basics of integrated pest management (IPM)…
The approach you take to gardening can make a huge difference to your garden’s productivity AND susceptibility to pest insects. We recommend that you have an organic, integrated pest management (IPM) plan which includes the following:
1. Biodiversity and crop rotation
Biodiversity means growing multiple species of plants in close proximity, rather than simply growing a single species of plants. Polyculture versus monoculture.
A garden containing nothing but corn is likely to attract more corn-specific pest insects and soil pathogens than a garden with multiple species (like the Native American polyculture system of Four Sisters – corn, beans, squash, sunflowers/bee balm, which very often contained additional plant species as well).
Similarly, if you have a high density of one type of plant (such as tomatoes) in one of your beds one year, wait a couple of years to plant tomatoes in that bed again, unless you’re planning to remediate any pathogenic microorganisms that have built up in the soil with hot compost or worm castings.
2. Healthy soil
Healthy, stress-free plants that are getting all the nutrients and water they need are much less likely to attract pest insects and much more likely to fend off those pests if they do come.
We highly encourage you to focus on long-term biological soil fertility using no-till organic methods. As we’ve written about elsewhere, synthetic nitrogen fertilizer doesn’t just damage your long-term soil health, hundreds of research studies have also concluded that it causes your plants to attract more pest insects.
3. Predatory insects
Every healthy ecosystem has predator-prey relationships that keep populations in equilibrium. Unfortunately, insecticides don’t discriminate between good and bad insects, so you tend to also wipe out your predators, which then creates an opening for an over-proliferation of pest insects.
Instead, try to create ideal habitat for your predatory/beneficial insects, who will operate as your pest control agents 24-7. This means:
- Adding lots of different types of flowering plants into your system that produce pollen & nectar at different points throughout the year (most predatory insects also eat nectar or pollen).
- Not tilling your soil, since many predatory insects overwinter, nest, or lay eggs in your soil.
- As best as possible, leave any crop debris from non-diseased plants on your soil surface or near your garden beds since there are likely predatory insect eggs (and yes, pest eggs too) on the debris – this also helps feed your soil as the old roots are decomposed by microorganisms.
If you use the three strategies above, you should be able to keep most all pest insects under control. However, there may be certain types of insects that present more of a problem or certain years when it’s very difficult to control your brassica pests without direct intervention.
Common Pest Insects On Kale & Other Brassicas… And How to Control Them Without Synthetic Pesticides
The four most common brassica pest insects that we encounter — and our recommended method/s of controlling them — are as follows:
Aphids are tiny sap-sucking insects that can reproduce exponentially if left unchecked.
On indoor seedlings, aphids can be a problem since there aren’t likely to be predatory insects inside your home. If you’re uncomfortable squishing them by hand or your seedlings are too delicate to withstand a blast from a kitchen sprayer (to knock the aphids off of your plants), neem oil will do the trick on your indoor seedlings.
Outdoors, aphids are a favorite snack for countless predatory insects. If you’ve taken the three pest management steps outlined above, you should have ladybugs, parasitoid wasps, lacewing larvae, and many other predators coming in to manage the aphid populations for you.
However, if you have an infestation that you want to deal with immediately, blast them off of your plants with water from a hose sprayer. If the problem continues to persist, consider buying & introducing lady bugs or using neem oil spray.
2. Cabbage White Butterfly Caterpillars (Pieris rapae)
Cabbage White Description:
The green larvae/caterpillars of the deceptively beautiful cabbage white butterfly which chew holes or eat entire leaves on brassica plants.
Cabbage White Control:
Birds and predatory insects eat the adult cabbage white butterflies. Many predatory insects eat or parasitize the caterpillars.
As with cross-striped caterpillars (below), you can use OMRI listed Bt spray (Bacillus thuringiensis) to get rid of an existing problem or Agribon ultra-light floating row cover to prevent the adult butterflies from laying eggs on your plants in the first place (it lets light and rain in, but keeps pest insects out).
3. Cross-striped caterpillars (Evergestis rimosalis)
Images of adult moths, chrysalis, and larvae can be seen here.
Cross-striped caterpillar description:
The green, black, and white-striped larvae/caterpillar of a rather plain looking brown moth. They can wreak havoc on your brassica leaves in the spring. We mostly see them on kale and cabbage.
Cross-striped caterpillar control:
Our paper wasps LOVE to hunt cross-striped caterpillars and cabbage white caterpillars, but we’ll also remove the caterpillars by hand and feed them to our ducks.
You can use OMRI listed Bt spray (Bacillus thuringiensis) to get rid of an existing problem or Agribon ultra-light floating row cover to prevent the moths from laying eggs in the first place (it lets light and rain in, but keeps pest insects out).
4. Harlequin Bugs (Murgantia histrionica)
Harlequin bug description:
Harlequin bugs and their nymphs are black and orange stinkbugs that suck the sap out of brassica leaves, leaving them covered with dried, brown spots. More serious infestations can kill the entire plant.
Unlike common stinkbugs, Harlequin bugs don’t emit any odor.
Harlequin bug control:
Harlequin bugs are our worst brassica pest and they don’t seem to have too many natural insect predators. We pull them off our plants and drop them into a bowl of soapy water whenever we see them.
Anytime we see them on a brassica plant, we also carefully inspect the plant for their eggs, which look like clusters of tiny black and white beads. As University of Florida extension says, Harlequin bug eggs are “marked by two broad black ‘hoops’ and a black spot.” (See above photo.)
*Note: If you live in the southeast, be especially careful not to confuse Harlequin bugs with Florida predatory stinkbugs (Euthyrhynchus floridanus), a great predator that you want to have around. We’ve seen our Florida predatory stinkbugs eat pest stinkbugs, Japanese beetles, and other pest insects in our yard.
Organic Gardening Pest Control Supplies
We hope this article will help you control your brassica pest insects using organic methods! You can use the Amazon affiliate links in this article to purchase the recommended products or shop for more organic pest control supplies here in the GrowJourney organic gardening supply store!