Cool-season gardeners know it all too well: the case of the disappearing brassica. You did everything right from monitoring your soil temperature to amending your soil. Your kale, cabbage, cauliflower and broccoli plants were all so perfect in their infancy. Before you could even harvest enough to make a respectable kale caesar salad or cabbage apple slaw, you notice the leaves starting to look like Swiss cheese.
Most gardeners can spot big threats to their gardens like Japanese beetles, aphids, groundhogs and deer. But, the sneakiest and sometimes the most destructive pests are those you can’t easily see, like the little green larvae of the common cabbage moth.
Cabbage moths are everywhere – they’re those common white moths that are flitting about your yard all the time. Yeah, that’s the one…sitting on your kale plant right this second and LAYING ITS EGGS!
In order to control any garden pest without chemicals, you need to first understand them and their life cycle. The cabbage moth itself is not harmful to your garden, it’s their hungry larvae that will eat holes in all your brassicas and they are small and incredibly good at camouflage. Sometimes, I can stare right at a leaf and not even see the big, fat, soft cabbage worm that’s destroying it.
The adult cabbage moths begin by laying individual eggs on the plant’s leaves, usually on the underside. The light greenish eggs are pretty easy to spot-look for small, individual kind of pointy dots often along the leaves’ margins. The eggs hatch and the cabbage worms begin to feed on the leaves until they are ready to pupate. They will then spin a silk pad to attach themselves to a plant and emerge as adult moths to repeat the cycle all over again.
How to Control Cabbage Worms Naturally
- Keep the moths out. At least while your plants are small, use a floating row cover to keep the moths from laying eggs on them. This will prevent at least one generation of cabbage worms from even happening.
- Kill the eggs. If you don’t want to cover your plants and you have a small garden, you can control cabbage worms with diligent inspection of the plants and smooshing of the eggs. Look at each individual leaf, especially on the undersides, and rub off any eggs you see.
- Handpick the cabbage worms. If you didn’t jump on this early enough and now you’re noticing holes in the leaves of your plants, it’s likely you already have some cabbage worms. Inspect the holes in the leaves and around the perimeter of the holes, you can see the worms if you look very closely. They may be quite small, or they may have grown to nearly an inch long. Handpick those worms and either drop them into a cup of soapy water or feed them to your backyard birds.
- Use Bt. Bt is short for bacillus thuringiensis and it’s one of the safest pesticides you can use in the organic garden. Bt is a naturally-occurring bacteria that, when eaten, makes cabbage worms sick and kills them. Bt will do no harm to beneficial insects or bees because it only works upon being ingested when it’s coating plants’ leaves. Bt is a perfect alternative if you have too many plants and it’s not feasible to inspect and pick off eggs and larvae. But, be very careful not get Bt on any plants that are hosts to good caterpillars like black swallowtails or monarchs.
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