Have you ever wandered out into the garden to find your broccoli, kale, collards or cabbages decimated by caterpillars or pillaging pigeons? Then you’ve fallen victim to a brassica massacre! If you’re ready to throw in the towel on brassicas because of all the pests that come with them, read on or watch our video to discover natural, no-chemical ways to fight back so you can enjoy healthy harvests of these must-grow veggies.
Common Brassica Pests
In my garden there are two pests that bother my brassicas more than any other: caterpillars and wood pigeons! Early summer (or even earlier in warmer climates) is the time when cabbage white butterflies and diamondback moths come out to play, ready to wreak their worst. Their caterpillars, also known as cabbageworms, devour young plants, eat holes in leaves and, in some cases, strip leaves down to their midribs, leaving plants skeletal shadows of their former selves. Your job, as gardener, is to catch them long before they cause too much damage, ideally blocking them altogether.
Through winter and then on into spring it’s the turn of those pigeons. With less to eat in the wider countryside, these hungry birds with their hearty appetites turn to our gardens. Here they’ll make short work of brassicas, tearing at the leaves as they feed, leaving them ragged and bare.
Other common pests include cabbage aphids and whitefly, which take to the air in clouds when disturbed. Many of these bugs will hide on the undersides of leaves, so when looking for them, be sure to thoroughly check plants all over – top and bottom!
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Whitefly lurk on the undersides of leaves and take to the air when disturbed
Step 1: Reduce Pest Risk
Prevention is better than cure, so employ tactics to keep pests from ever bothering your brassicas in the first place. Plant flowers that are known to confuse or repel pests, often because of their strong scent, including aromatic herbs and flowers such as marigold, hyssop, mint, and thyme. Each of these has, to some degree, the ability to confuse or ward off pests, including aphids, mites, and cabbage moths.
Combine these plants with flowers known to attract pest predators. Flowering herbs like parsley, dill, basil or cilantro are great because the bugs like their simple, small flowers. Just be aware that these need to be in flower early enough to attract the predators, so that may mean starting herbs off indoors to have them at the ready to plant out in good time. The natural presence of predators like ladybugs should help to keep pest populations at a manageable level throughout the growing season.
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Attract hoverflies with flowers and their larvae will feed on pests like aphids
Confusing pests is a superb tactic to deploy. The nature of my garden with its smaller beds means that I don’t tend to grow loads of one crop at any single time or in any one spot. Rather, plants are grown alongside other crops and flowers that belong to different plant families. This makes targeting specific plants a little harder for would-be pests, because what they’re faced with is a tapestry of plants, intricately woven together.
Be sure to remove weeds belonging to the brassica family from around your vegetable garden as these might serve as a hosts for brassica pests, giving them refuge in between crops. Examples of brassica weeds are arugula, stray canola oil plants, mustards, hairy bittercress and shepherd’s purse.
Use bird feeders to attract insect-eating birds to your garden. Through regular feeding you’ll have them coming back for more – and they’ll be on the lookout for tasty insect morsels throughout your garden too!
Cabbage root maggots can feed on the roots of brassicas, causing plants to wilt. You can buy purpose-sold cabbage collars to prevent this or just cut a circle of cardboard, cloth or heavy paper, then cut a slit to the middle and install this as a skirt around the plant’s main stem. This simple method protects plants from egg laying by adult cabbage root flies.
Step 2: Build Barriers
All the measures above can be highly excellent, especially if used in combination. But the most secure step of all is simply to keep plants covered so none of these pests can ever get anywhere near your plants!
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Use netting to stop pests from ever reaching your crops
Let’s talk through the different covers you can use. First off is butterfly netting, which has holes less than quarter of an inch (5mm) across to stop even the most determined butterflies from gaining access. To prevent butterflies from laying their eggs through the holes you’ll need to suspend the netting so that it’s held up off your plants. A simple frame made of bamboo canes with upturned plastic bottles on the ends works well, but be sure to secure the netting at the edges to stop pests from getting in at ground level. I’ve seen this type of butterfly netting stapled onto a wooden frame to make a very simple but effective protective box for vulnerable seedlings – I love the ingenuity of this!
I like to use tightly woven nylon insect mesh to keep pests off. It’s really durable so should last for quite a few seasons, no problem. Despite being very tight-knit it will let plenty of light and rain through. It will keep butterflies and moths, cabbage aphids, and cabbage root maggots out. Secure the edges with bricks or boards so there’s no opportunity for pests to sneak in under the mesh.
Alternatively, you could make a temporary miniature hoop house frame then secure the mesh over that. Because of their curved shape these stand up to the wind really well, so are a great choice for more exposed gardens. Use plastic piping (for instance gas pipe or water pipe) cut to size and slid onto uprights of bamboo cane or rebar. Keep your tunnel rigid by tying a bamboo cane to the underside of the apex of the hoops with string.
I like to use tightly woven nylon insect mesh. It’s really durable so should last for quite a few seasons, no problem. Despite being very tight-knit, it will let plenty of light and rain through. It will keep just about every pest out: butterflies of course, plus cabbage aphids and cabbage maggots too. Secure the edges with bricks or boards so there’s no opportunity for pests to sneak in under the mesh.
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Repair any holes in netting before pests find their way inside
As an alternative to insect mesh you could even use dressmaker’s tulle or netting. It often works out a lot cheaper than insect mesh, and you can even bung it in the washing machine at the end of the season to freshen it up!
You can leave these covers on all year, but in the winter months it can be a good idea to swap to a wider mesh bird netting to keep those pesky pigeons off. Bird netting is less prone to sagging if it snows heavily, and is less likely to catch the wind and get blown away.
It’s important to have covers in place in advance of any attack, so always err on the side of caution. Take precautions when removing covers to tend your crop or to harvest. Check around plants meticulously to avoid accidentally trapping a pest beneath the cover so it can’t escape – the worst possible outcome! Check your covers regularly and make any repairs as necessary. A few small holes may go unnoticed but over time they will get larger, offering an open invitation to passing pests.
Step 2: Seek and Destroy
But what if your plants do get infested with caterpillars or aphids? Well, if you are checking plants regularly and spot the problem early enough, you stand a fair chance of stopping it before it gets out of hand. You can cut off the worst-affected leaves and just ditch these onto the compost heap.
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Act fast when you spot pests to avoid a total crop failure
If you’re growing only a few plants it shouldn’t be too big a job to pick caterpillars off by hand. Do with them what you will: feed them to your chickens, dispose of them in a bucket of water or, if you can bear to do so, squish them.
Some gardeners plant nasturtiums close to their brassicas to serve as a sacrificial or trap crop – basically a plant grown with the specific intention of luring a pest away from the crop you want to grow to eat. Nasturtiums, with their soft, fleshy leaves, are a cabbageworm’s favorite! Another great sacrificial crop are collards. Once they become infested remove the plants, taking the caterpillars with them, and compost them.
Another option is to spray plants with Bt (Bacillus thuringiensis), a naturally occurring bacteria found in soil. Caterpillars that ingest the bacteria ultimately perish. The good news is that Bt won’t impact other insects and, being a naturally occurring bacteria, it is totally safe, and considered organic. That said, it can affect other butterflies and moths, so spray it carefully, making sure to spray on a still day and to only spray on your brassicas. Spray uncovered plants regularly, according to the instructions, to keep them protected.
I hope you’re empowered, pumped and primed to grow brassicas, safe in the knowledge you can beat the pests!
