Organic Gardening with Caterpillars on your Brassicas

Organic Gardening with Caterpillars on your Brassicas

August 20, 2017 Off By Keep It Green

Organic gardening with caterpillars can be tricky

After the rain came the butterflies.

As beautiful as they are, butterflies have chosen my brassicas to be a nursery for what seems like a gazillion caterpillars.
It’s my fault for not netting them in time, I had no problem with the seedlings, but after a few heavy summer rains the butterflies got busy, and before I knew it my Kale had turned into skeletons of their former deep green leafy selves, my purple sprouting broccoli became a great place for hide and seek whilst being massacred and my sprout leaves have turned into a Swiss Cheese.

I accept the inevitable, and willingly sacrifice some of the crop to sustain these creatures because I want to help our natural wildlife thrive, but I’d also like to have some sprouts with our Christmas dinner.

Caterpillars and organic gardening

Where have all the garden birds gone?

The natural back garden preditor

Answers in the comments below if you have any ideas please.

The natural order of things.

What has made this more noticeable has been the lack of garden birds to reinforce the natural food chain of events. I’m happy to leave nature to get on with managing itself and even encourage it by building a bug hotel, but when one part of this chain is absent another link begins to dominate.
So where are all the garden birds? A month ago I could spot gold finches, black birds, thrushes, blue tits, great tits, starlings, sparrows by the dozen, and now I’m left with a pair of bemused black ringed doves and a pigeon. They couldn’t get enough of the aphids, worms and creepy crawlies in June and early July but now it seems they’ve boycotted my garden. 

So, how to keep caterpillars off your vegetable garden

The plants may be getting destroyed but I just can’t bring myself to use chemical “pest” control in the garden, it’s just unimaginable. Besides, although they’ve gorged themselves on what I was hoping to be my prized Christmas dinner veggie centre piece, they are only doing what’s natural. So who am I to ruin their tea party.

Organic Gardening and caterpillars
Organic gardening with caterpillars

Four ways to prevent caterpillars from eating your brassicas

  1. Soapy water is one idea, something more eco friendly than the regular chemical cocktails available on the supermarket shelf is in order though. This one looks okay, Bio D Washing-Up Liquid 5 litre, or something similar.
  2. Before the butterflies descend in May, a regular garlic spray is supposed to be a deterrent to insects laying eggs. (See method for making this below). It’s also apparently good for deterring wild rabbits from munching their way through your allotment. So a good all rounder, and I like garlic in my salad dressing.
  3. Pick them off. Well it’s back breaking work but you do gain an appreciation of their efficiency for survival.
  4. Net your crop. Deny the beast access to the nursery. There are some cool Crop Cages as well. More than tall enough for the sprouts.

I’ve taken to breaking off the worst effected stalks (no leaf left) and placing them, still with caterpillar attached, on the compost heap. New growth seems to be fine from the centre of the plant, even after quite a brutal pruning. So I’m slowly clearing the creatures and going to place a net over the remaining stalks in the hope that they will recover, although I reckon the vigil isn’t quite over yet.

Common UK garden butterfly
The Cabbage White

“Organic Pesticides” it's a matter of perspective.

Read the labels carefully, you are now entering the advertisers world of subconscious retail manipulation.

PYRETHRUM comes out on top as the most effective “organic” pesticide, (the word ‘pesticide’ makes me cringe by the way). However, Pyrethrum is also considered to be the most potent of organic chemicals to use in the garden. To give this a commercial perspective, I’ve found that Pyrethrum is synthesised and relabelled ‘Pyrethroids’, and you’ll probably find this listed on the back of most nasties on the garden centre “shelf of death and destruction”.

However, luckily Pyrethrum is derived from a variety of daisy, which one could plant amongst the veg plot as a natural deterrent, being synthesised and concentrated rings alarm bells, so think carefully if you are considering the alternative route.

A natural caterpillar deterrent
Where to grow Marigolds

I mean, just to go off on a tangent for a moment, why use ANY of these chemical death sprays near or, boggles the mind, ON your fruit and veg when no one in their right mind would put any of the compounds in their salad dressing and serve it to their children.
Anyway, even though the RHS lists Pyrethrum as an organic pesticide it also warns of the danger to pollinating insects. So it’s not exactly bee friendly in it’s processed form. You’ve really got to do your research and read articles in full to get the full story.

Then again, the PYRETHRUM daisy, or ‘Painted Daisy’ in it’s natural living form is a marvellous plant to have around to attract pollinators, as well as deterring the pests when planted in amongst your veg , especially when mixed in with the Marigolds. Definitely something I’m going to do next year.

Organic Vegetable Gardening

So if you don’t want to kill the caterpillars, that’s it really. Be willing to sacrifice some of your brassica for their benefit and enjoy the resulting wildlife. Spray some garlic solution on the other plants, net them and sow marigolds and Painted Daisies. It’s going to look fantastic.

How to make Garlic Spray

This Garlic spray recipe is generally an effective repellent but will kill some soft-bodied insects. Spray regularly for maximum effect, especially after rain.


In a litre of water add

3 large cloves of crushed garlic
1 teaspoon of non toxic liquid soap 
1 tablespoon of vegetable oil (this helps it stick and prevents the solution from washing away immediately)

Crush the garlic and mix with the vegetable oil and leave in a jar overnight to infuse.

Next day strain out the garlic and add to the water, add a teaspoon of the liquid soap.
Pour into a spray bottle (preferably recycled, just make sure it’s clean and that there are no chemical residue left) and spray on the upper and lower sides of the leaves. Don’t over do it though.

I also use baked and ground up egg shells around the base of soft stem pants to deter slugs and snails, this is also a good source of calcium.
Don’t forget that a fine net or crop cage raised above the brassicas will prevent butterflies from laying eggs on the leaves without hurting them. Make sure the net or cage doesn’t rest on any of the leaves, otherwise the butterfly can still lay their eggs through the netting.

If you do have any other ways of protecting the your organic vegetables from insects do share in the comments below or tag @agreenerlifeuk on Twitter to get our attention.

Lets look at this another way.

How to look after butterflies on your veg plot.

The (Scientific names: Pieris brassicae, Pieris rapae, Mamestra brassicae aka) Cabbage White butterfly 
is most active between May and October, and although only munching it’s way through my broccoli for about 2 ½ weeks before leaving the plant to pupate, a large number of them will still decimate the crop, so netting a proportion of the crop and leaving other areas open for them to feed on seems to be the best wildlife friendly option.
I get to enjoy the butterflies and the species lives on. The birds also get to enjoy the caterpillars for lunch, when they turn up.

Have a look at some butterfly feeding stations from the RSPB, you and the children could try them out in your wildlife garden. I believe orange slices are also one of their favourite treats.

Attracting butterflies into the garden
Owl Butterfly

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