Caterpillars!!
The battle with these worms is real, and they are the bane of my frustration this season in the garden. Those white butterflies are pretty, but you can be assured that if your crops are not protected,
they will deposit their offspring onto your plants. Cabbage moths or butterflies don’t directly damage plants. That fun job is left up to their larvae—the worms!
Cabbage worms is a relatively generic term for a handful of small green pest caterpillar species. As their names suggest, they are most attracted to the cabbage and mustard plant family, also known as the brassica family. This includes broccoli, kale, collard greens, Brussels sprouts, mustard greens, turnip greens, and cabbage. I have also found them on various flowers, and they love nasturtiums / kappertjies.
When it’s time for the female cabbage white butterfly to lay her eggs, she seeks out plants known as “crucifers.” Then she deposits her eggs on the undersides of leaves, where wormlike larvae hatch two to three weeks later. Cabbage moth eggs look like white or yellow oblong dots. If you find and recognize these eggs, squishing them is a great early control method!
While the adult butterfly feeds on nectar from flowers, its newly hatched larvae seek other food. As the larvae of cabbage moths and butterflies emerge from their eggs, the cabbage worms feed on the surrounding plant matter immediately. This creates little holes in the leaves, expanding to larger holes or completely demolished leaves and plants as the caterpillars grow in size and population, and this happens fast!
Caterpillars are the larval stage of butterflies and moths. Several species feed on cabbages, other brassicas, and other plants, including turnip, swede, horseradish, and nasturtiums.
The three species that are often found are:
- Large white butterfly (Pieris brassicae)
- Small white butterfly (Pieris rapae)
- Cabbage moth (Mamestra brassicae)
Where possible, tolerate populations as cabbage caterpillars are food for many other creatures, including parasitoid and social wasps and birds.
How to protect your crop
- Growing brassicas under fine netting or horticultural fleece can exclude adult butterflies and moths from laying eggs on the crop. Care must be taken to ensure the netting does not touch the plants, or the adults can lay eggs through it.
- Inspect plants regularly and pick off the pale yellow butterfly eggs.
- Yellow sticky traps will catch the adult butterflies but may also catch beneficial insects. Use with caution
- Neem oil is effective against cabbage worms.
- Bacillus thuringiensis, or Bt, is a naturally occurring, soil-dwelling bacteria. It is a common active ingredient in organic biological pesticides. Bt kills caterpillars. However, it is ONLY toxic against the larvae of butterflies or moths. It makes them stop eating. Therefore, Bt is commonly used to control cabbage worms and cabbage loopers in the brassica plant family. (Buy yours here)
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Recipe for Cabbage Worm Spray
- 2 L of water.
- 2 tablespoons of castille soap (buy yours here) [1]
- 20 drops peppermint essential oil.
- 2 drops garlic essential oil.
Companion plants to keep cabbage moths away
- Celery – The scent of celery plants deters the cabbage moth.
- Thyme – Masks the scent of those plants susceptible to cabbage worms and moths.
- Mustard – Mustard makes an exceptional trap crop. Cabbage moths are drawn to mustard plants, which may keep cabbage moths away from your precious plants.
- Sage—Cabbage moths and carrot flies dislike the sage’s repulsive elements. Plant it in your cabbage plants’ borders to maximize its anti-pest properties.
- Borage – Repels cabbage moths and encourages beneficial insects.
- Chamomile- Repels cabbage moths and masks the scent of cabbage family plants.
Parasitic wasps lay their eggs inside or on top of other arthropods, including caterpillars and larvae. Beneficial insects can be a great tool against cabbage worms and other pest caterpillars like tomato hornworms. Once their eggs hatch, the wasp larvae feed on the host caterpillar, killing it. Read this posting on how to attract beneficial insects to your garden. [2]
Organic gardening can be a joy and sometimes very frustrating, but by using some of the above-mentioned methods to protect your crops, you will succeed in growing brassicas.
Happy gardening friends
Tash and Family