Summer of ’22, I grew brassicas out in the open without any insect mesh, from seedling to finish. I was feeling confident in my parasitic wasp population, and they didn’t disappoint.
What a turn around! For most of my garden life I haven’t bothered growing brassica through summer because the cabbage white caterpillars decimated them. However, gardens – along with life – are ever changing.
15 years gardening here, and the beneficial insect population – seduced in by my perennial companions, no dig and spray free ways – has grown and diversified. The flow on effect of all those predatory + parasitic insects is there’s a lot less pest management for me to do. Less psyllids, less aphids, and this last improvement – a gang of parasitic wasps who happen to live off caterpillars.
So while I’m not cabbage white butterfly free, they’re still flapping about out there – I am, at the moment, free from intensely managing them – the odd squash here and there goes on.
Notice the flexible statement. Lets not ever set anything down in stone – life is change!
4 ways to cabbage white freedom
Call in the beneficial insects
Beneficial insects are your long term, pest control strategy. As far as the cabbage white butterfly goes, there are three wasps I know of that come out to play.
- Braconid and pteromalid parasitic wasps use caterpillars as a mobile nursery. They lay their eggs in or on them, providing a delicious first meal of caterpillar for the youngsters upon hatching.
- Paper wasps kill and chew caterpillars, and bring them back to the nest to feed the young.
Some of you, I know, will be worried for the monarchs, but I prefer not to get too involved here, and leave the balance of these things to nature. I still have butterflies.
The way to a booming beneficial insect population is to feed and house them.
- Plant loads of perennial companions in order to provide a year round supply of nectar and pollen
- Spray no nasty chemicals – benies are more sensitive to herbicides and pesticides than pests are.
- Create densely planted areas for habitat.
- And let pest populations go for as long as you can bear – those pests are calling in the predators after all.
While you build your beneficial insect population, manage the cabbage whites by squashing caterpillars, flicking off eggs and/or covering the crop.
Squash the caterpillars
Focus on young seedlings. Remember to check your seedling trays too. Hungry caterpillars sure can eat and make short work of small plants. Squash any you find. Check under leaves for the creamy, bullet shaped eggs and flick them off.
Cover the crop
Insect Mesh is a god send. It keeps the butterfly from laying eggs, there by preventing the caterpillars in the first place. Don’t cover and walk away though – eggs may have been laid before covering. Always always keep your eye on the job.
Spray
Spraying is for the busy person who doesn’t have time to squash caterpillars or has no insect mesh available.
BT (Bacillus Thuringiensis) is the active ingredient in Kiwicare’s Organic Caterpillar Control, and Yates Natures Way Caterpillar Killer. For bigger gardens you’ll need more than these small packs. Farmlands sell a commercial pack of Dipel. Costs a bit so maybe a good idea to go splits in your co-op/ garden group/ neighbourhood.
Mix it up and spray it all over your brassicas fortnightly to keep up with the egg hatchings. BT only impacts those that eat the leaves which is what makes it safe for bees, ladybugs and all our other friends. The potential is, it will kill any caterpillar that munches the sprayed foliage, so bear this in mind.
Keep this job on your radar until the heat subsides and the cabbage whites disappear late autumn.
Derris dust alert!
Let’s stop with the Derris Dust. I know its easy. I know Grandma used it. But it’s super toxic! Rotenone, the active ingredient in Derris dust is a neurotoxin and fatal to many of our important beneficial insects – parasitic wasps, ladybirds and dragonflies to name a few. Canada has outlawed the use of it on gardens and looks like USA is going the same way.
Great news Kath, we’re just over the Ohau river and we’ve also had a good broccoli summer with a 5th way. My study window overlooks the veggie patch. As soon as I see a cabbage white butterfly I run outside and whack it with a fly swat before they lay their eggs. No chemicals. Now I just need to catch the scwewy wabbits.
Love it! Pest control, exercise and a flush of H2O for better brain power all in one go 🙂
Trouble is the blesséd paper wasps, knock out the native butterflies as well, and many of these are endangered! No free lunch here !!
so true Ashley. Always an interesting line to draw.
I just got a tip from my local garden centre to add a bit of lime into the planting hole. They plant will take some of it up and apparently the caterpillars can’t deal with it.
I haven’t tried it (in fact I forgot to add the lime while I planted them out last week, so may need to replant them this weekend), but wanted to share the tip anyway!
Interesting Helga! Thanks for sharing – it’d be great to try it and see what happens. I’m not sure about the lime in the bottom of the hole though – thats my gut feeling. Endless experiments in the garden 🙂
Planted celery amongst my brassica and have had garden any problems with caterpillars, seems they don’t like the smell. I’m sold on it anyway.
Cool one! Love this observation. Each garden is totally unique as are its solutions. If you see it working, then it is! Believe it 🙂
I flick the white butterfly eggs off the leaves, but I worry – could the eggs still hatch lying on the ground under the plant and then climb back up and start munching?
Hi Sheryl – I’ve been flicking off eggs forever and never had a problem here. Its interesting to watch and see yourself what happens. Kath
Hi Kath – Here in Melbourne (Victoria, Australia), we have loads of white butterflies, more than I have ever seen in my garden. I catch them mid air with a tennis racket and feed them to my chooks. They come running for them. I also pick off the caterpillar’s, put them in a shallow tin lid and give them to my chooks. They love all these natural treats and produce extra yellow eggs for me. A win win situation.
Perfect! I admire your enthusiasm 🙂
Always interested to read about what might work with the dreaded white butterflies. I’m still resigned to insect netting since it does work, except for the most cunning! I am interested to know your suggestions for codlin moth. Have read about pheromone rings, want to test Neem granules this year to see if they might work. Will search to see if you’ve advised on this previously.
Insect mesh is awesome! I havent written up a codling moth blog yet. This article is excellent https://thisnzlife.co.nz/organic-methods-control-codling-moth/
Would water get to the plants using a net like in your picture ? I am told old net curtains work but then someone else says that water/rain doesnt get to the plants.
oh yes it sure does! Old net curtains do keep out cabbage whites and also let in rain…. watch and see!
No problem with rain or hose water getting through insect netting.
Hi Kath, myself and friends have noticed a near absence of white butterflies throughout Nelson so far this year. We wondered if paper wasps are eating them or some new predator. Usually we all have to manage carefully. Any knowledge on this? It’s definitely not just because our gardens are improving
Nice! Something is managing the cabbage whites and its most likely at the caterpillar stage… so probs a predatory wasp. Take a suiet sit in your garden – brassicas are a good spot for this and park up and see whats going on. I’m sure your gardens are improving, by the way!
I’ve planted a few broccoli this week, as well as lupin in the bed. Couldn’t wait for lupin to come up and then chop down as I didn’t feel like growing them on this year. I will then pull out the lupin when they are small plants and lay it down as mulch/food around the growing broccoli. I did this recently with buckwheat and a few late zucchini, scallopini and marjoram in a bed and they are all doing wonderfully. The phacelia is just coming up around them now. I’ll do the same with that in this bed. Always leaving a few to flower of course. Not as good as leaving the plants to properly green crop, but next best…it works and builds soil.
It sure does Diane, works a treat. What an awesome pattern you’ve got going on!
I read that diatemaceous earth works for the cabbage caterpillars, do you know if this works?
Hey Alison, it likely would impact but I cant advise as I dont use it in the garden – my concern being the bees transporting it back to hive and impacting the brood.