Cabbage White Butterflies – How to Avoid a Brassica Massacre

, written by Ann Marie Hendry gb flag

Cabbage white butterfly

Like many gardeners, I've been unfortunate enough to experience some brassica damage in the past. A few tattered rutabagas, a holey kale plant – tell-tale signs that Small Cabbage White butterflies had laid their eggs on my plants. I considered the damage annoying, but it never reached really troublesome proportions in my garden.

Last year when I spotted large numbers of Cabbage Whites flying around, I didn't pay much attention to them at first, as I had (fortunately, as it turned out) decided not to grow any brassica crops. I do grow nasturtiums along the vegetable patch fence however, and within a matter of days I went from 'Oh look – that's an interesting caterpillar' to 'Eek! What are those caterpillars and what have they done to my nasturtiums?'

Large and Small Cabbage White Butterflies

It turns out that the Small Cabbage White butterfly, while undoubtedly a pest, is nothing compared to its big brother, the unimaginatively-named Large Cabbage White. The two are very similar, but the caterpillars, or cabbageworms, are distinct – the Small Whites are an unassuming pale green colour, while the Large White larvae sport a hairy black and yellow jacket.

Cabbageworms

Both butterflies are widespread throughout Britain and Europe, and the Small White has also been introduced to North America, Australia and New Zealand (sorry guys!), where it's often known as the 'imported cabbageworm'. If it's any consolation, the Small White is less of a voracious feeder than the Large White – as I discovered, when half a dozen robust nasturtiums were reduced to skeletons.

As the name suggests, cabbages and other brassicas are the favored food plants of the Cabbage White larvae. The butterfly will lay eggs on the undersides of leaves (singly in the case of the Small White, in groups of 40-100 by the Large White) and after a week or two the larvae will emerge, like the Very Hungry Caterpillar in my favorite childrens' book, ready to eat whatever lies in its path. Small Whites will tunnel into the hearts of cabbages, so even if they're around in fewer numbers, a handful of larvae can still do serious damage to your crop.

Protecting Against Cabbage Whites

So how do we stop them from destroying our crops? Well, prevention is always better than cure, so the first step is to invest in some good, butterfly-proof netting. I've draped mine over hoops to make it easy to throw it back for weeding or harvesting, but you can lay it directly on top of the plants.

Small cabbage white caterpillar damage

Make sure the barrier is firmly held down at the edges, with no gaps that butterflies could squeeze in through – I prefer to use bricks rather than pegs, which tend to tear netting and shorten its life. Alternatively, burying the edges into the soil will make absolutely sure that there are no gaps.

You can use the Netting icons in our Garden Planner to mark on your plan where you need it in your garden. If you're not sure which of your crops are likely to be affected, use the Custom Filter button to show only brassicas in the selection bar, and group these together under your netting.

Cabbage Whites produce two broods per year (three in a favorable summer), so make sure to install the netting in spring and don't remove it until autumn. Even under netting however, regular inspection of leaves is essential. Hand-picking eggs and larvae off the plants can be laborious, but it is effective. Small White larvae are well-camouflaged, so make sure to check the ribs of leaves where they often hide. Growing red-leaved varieties of cabbage and other brassicas can make it easier to spot them.

Cabbage white butterfly

Cabbage White Predators

As any organic gardener knows, encouraging natural predators is a great way to control pest populations (and saves you having to perform grisly executions personally). Cabbage white larvae have a trick up their sleeves though – they accumulate mustard oil in their bodies from the food plant, which makes them unpalatable to most predators. Some birds will still eat them however, so it's worth providing feeders and nest boxes to encourage insectivorous birds such as house sparrows, goldfinches and skylarks into your garden.

Large White cabbageworms can fall prey to the larvae of Apanteles glomeratus, a parasitic wasp, which devours the caterpillar from the inside out, carefully avoiding the vital organs so the host continues to grow to full size. If you find any dead caterpillars with yellow cocoons next to them, it might be worth moving them among your brassicas so that the parasites will attack further generations.

Once fully grown, the larvae will move away from the food plants and make their way to somewhere sheltered such as a fence, shed wall, or tree trunk, and pupate for around two weeks in summer, or eight weeks for overwintering pupae, so it's a good idea to check these areas and remove any you find.

Surprisingly considering the devastation wreaked on my nasturtiums I didn't find a single pupa over the winter, but spiders seemed to have a feast on the larvae last year and I've seen butterflies caught in their webs this year too.

Despite the likelihood of total annihilation, I am growing nasturtiums again – hopefully their presence will distract the butterflies from trying to squeeze in under my netting and I'll enjoy a good crop of broccoli later this summer!

By Ann Marie Hendry.

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Comments

 
"my cabbage is attacked by very tiny flies...Black dots like. and also I saw someclusters of white dots like things and when I touched them they were like ashes :( what to do now....any home remedies?"
babra on Thursday 19 February 2015
"Hi Babra, I'm not sure what's affecting your cabbage I'm afraid (aphids perhaps?) but I'd recommend hand-picking all of them off (or use a jet from a hose to dislodge them) and then protect your plants with netting so insects can't get near them. I hope that helps!"
Ann Marie Hendry on Friday 20 February 2015
"thx ann for ur suggestion... I will try that :)"
babra on Sunday 22 February 2015
"Hi babra my names dave what u have on your cabbage is blackfly and white fly they suck the sap from the plant and stops it growing my cure is a spray bottle with a little dish soap thos will not harm the plant's and you will need to do this every three days hope this helps"
david on Friday 27 February 2015
"Thanks for a very interesting article on cabbage white butterfly. I intend to cover my young cabbages with a net but I wanted to ask you what experiences you have about the butterflies flying low...? I note that you put your netting right down to the ground. If I left a 15 cm gap at the bottom, do you think they would get underneath? Thanks again for a really informative web site! "
Sally on Tuesday 17 November 2015
"Hi Sally, sorry for this extremely tardy reply! The netting really does need to be right to the ground, with the edges securely weighed down or buried in the soil."
Ann Marie Hendry on Wednesday 18 May 2016
"What ever happened to using Sevin or Eight?? I always plant my cabbages where I can see them from the door, then when I see the butterflies, I sprinkle it. "
C.J. on Thursday 2 June 2016
"There have been a couple studies done about using upland cress as a dead end trap crop for the cabbage white. They prefer to lay their eggs on the upland cress, but then the caterpillars can't eat it so they die. This is the first year I've used it, but I haven't seen a tenth of the caterpillars I have in years past."
Sara (Zone 5) on Tuesday 28 June 2016
"I saw many cabbage whites laying eggs on my brassicas this year, but no caterpillars - I think they must have all been taken by the wasps which were constantly patrolling the garden."
John on Friday 16 December 2016
"There's a very good chance you're right John. What many people don't realise is that wasps feed meaty morsels to their young, and in doing so make an extremely valuable contribution to garden pest control."
Ann Marie Hendry on Friday 16 December 2016
"That's an interesting insight Sara. I believe upland cress is also known as land cress, and it's easily available from seed companies. I may have to try that - thanks for sharing!"
Ann Marie Hendry on Friday 16 December 2016
"Hi do you post to Australia? thank you David"
david on Sunday 12 March 2017
"Hi David, we don't sell any physical products. Our garden planning apps (click the Planner link in the menu bar at the top of the page) will work in Australia however."
Ann Marie Hendry on Wednesday 15 March 2017
"I wouldn't advise laying the netting directly on the plants, as the cabbage whites will just lay their eggs through the net onto the leaves of your brassicas, even sticking their abdomens through to reach a leaf just below or inside the net. It should be kept at some distance from the leaves in all directions on a frame of some kind."
John on Tuesday 2 May 2017
"Indeed John - I cut down yellow gas pipe to make hoops to drape netting over, and many people use the blue water pipe, which is very similar. Alternatively, any metal or wooden structure can be used as long as there are no sharp corners. For the simplest solution, use bamboo canes with flowerpots or burst tennis balls over the ends to stop the canes poking through the netting."
Ann Marie Hendry on Tuesday 2 May 2017
"When do cabbage white butterflies appear"
Keith Boden on Friday 23 June 2017
"I'm in Cornwall near St Ives. The last few years although I haven't seen butterflies I've found caterpillars on my brassicas throughout the winter. They look like cabbage white but are very large only one or 2 at a time. Will be getting netting and will keep it up year round. It's surprising how much damage just one or two of them can make."
Carol Ann on Saturday 24 June 2017
"Will need oil or diatomaceous earth help with these cabbage white butterflies?"
Deborah Butcher on Sunday 25 June 2017
"What time of year do cabbage whites appear? my netting is fit to burst now and i'm wondering should i remove it as the plants are already well established? Thanks"
Dom on Monday 26 June 2017
"1st Cabbage White Butterfly seeen in garden in Shenstone, Sth Staffs. 3rd July and another today 5th. Too late. Picked me first cabbage yesterday. Untouched by the little bu**ers!"
Keith Boden on Wednesday 5 July 2017
"Yes I see them now, loads of them and they are inside my netting (my netting is bursting at the edges...note to self, bigger netting next year!), im using a shoot to kill policy all over the garden...im making room for red admirals and the like!"
Dom on Wednesday 5 July 2017
"Hi Keith, that's interesting - I haven't seen them here yet, but I'm a bit further north than you, in the south of Scotland. Please do report any sightings of pests (and beneficial insects too) at www.BigBugHunt.com - we're working to create a pest prediction service which will use data provided by gardeners about when and where bugs are seen to advise when bugs are likely to appear in your area."
Ann Marie Hendry on Wednesday 5 July 2017
"Our nasturtiums are being eaten by a swarm of large cabbage catepillars We have courgettes in the same bed should we be worried about them ?"
Janet on Wednesday 26 July 2017
"The caterpillars of cabbage white butterflies will only feed on cabbage family plants Janet. This includes nasturtiums unfortunately. Your courgettes will be safe!"
Ann Marie Hendry on Wednesday 26 July 2017
"I nhave used a net to try and keep the cabbage whites at bay. I put poles aruond the crop then placed plastic milk bottles over these then the net. This prevents holes etc,"
Graham on Sunday 13 August 2017

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