Over the years the Harvest farm shop has had all sorts of visitors from the animal kingdom including a goldcrest bird, duckling, a frog and various moths and butterflies. Today in the shop we had 2 visitors from the local world of insects, winged cousins, a small cabbage white butterfly and a close relative of butterflies, a poplar hawk moth.
The impressive hawk moth was brought into the shop for an identification by a friend of Harvest and the butterfly emerged from the batch of kale delivered this week.
There are about 59 uk butterfly species but there are an incredible 2500 species of uk moth with the hawk moths being amongst the largest.
A few caterpillars of both butterflies and moths can cause some damage to leafy crops, It is the time of year when cabbage white seek out members of the brassica family on which to lay their eggs. There are 2 cabbage white butterfly species which are considered pests of brassica, the small white and large white. Gardeners and growers are most familiar with the large white as they lay numerous eggs which hatch out into greenish caterpillars, these eating machines can render a cabbage, kale or cauliflower looking like a skeleton, In most cases the damage is brief and the plants recover fully after the caterpillars pupates.
Organic and agro-ecological farmers and gardeners do not use chemicals such as powerful pesticides which also harm friendly wildlife and the health of the soil, instead they build good soil health and provide habitats and wildlife corridors for nature and the many predators of pests, particularly encourage parasitic wasp which seek out their caterpillar prey, the cabbage white caterpillar and lay their eggs on them. The wasp larvae hatch and begin to feed on the hosts insides of the caterpillar avoiding its vital organs until it is ready to morph into an adult wasp when it eats its way out and pupates. The predated caterpillar will never reach the butterfly stage so helping to keep things in balance.
The female cabbage white locates the brassica host food plant to lay its eggs by tasting for the mustard taste of the plant with its feet often flitting to a few cabbage plants together to choose a site to lay its eggs. Brassica planted with other plant species in a polyculture can confuse the cabbage white and reduce potential damage. If the cabbage plant is established and healthy, it will fully recover after being decimated by caterpillars. Gardeners who want to avoid any damage to the cabbage patch often use a physical barrier such as netting or enviromesh to keep pests off. Beware tho, netting can be lethal for other wildlife such as hedgehogs who will easily get entangled in netting and die.
Another predator to the cabbage white caterpillar is the less known carnivorous spiked shieldbug, the bug devours its victims by sucking out its body juices through its spiked mouth part.
Moths and butterflies are a vital food source for bats. Moths, butterflies and caterpillars are eaten by many other animals including other insects, spiders, frogs, birds, toads, lizards and mammals such as bats, hedgehogs & shrews. It may come as a surprise that the large cabbage white butterflies have evolved to be toxic to most birds and this is why robins, blackbirds etc leave them alone so this is why the parasitic wasp is an important predator.
As with almost all garden friends, one of the best habitats for wildlife is a patch of undisturbed, unmown nettle patches, all the better if theres a pile of rotting logs among it.
One butterfly which often gets mistaken for a cabbage white is the orange tip butterfly which appears in the spring. The food plant of the orange tip caterpillar is the pretty meadow flower the cuckoo flower. The male has the bright orange tips to its wings where this species gets its name from but the female has plain black and white wings.
So much of the natural worlds ecosystems have been damaged by industrial farming and the over use of chemicals that insects have been in decline, Harvest Workers Coop only work with farmers and producers who farm organically without chemicals and without artificial fertilisers and who care for the environment.
Protecting Against Cabbage Whites
Since it’s always better to prevent than to treat, the first thing we should do is invest in some high-quality, butterfly-proof netting. To make it simple to throw it back for weeding and harvesting, I’ve draped mine over hoops.
Make sure the barrier is securely fastened at all edges, with no openings for butterflies to pass through. Bricks work better than pegs, which have a tendency to rip netting and reduce its lifespan. As an alternative, burying the edges in the ground will ensure that there are no gaps at all.
The Garden Planner’s Netting icons allow you to indicate on your plan where you need netting in your garden. If you’re unsure which of your crops will be impacted, group your brassica crops under your netting by using the Custom Filter button to display only brassicas in the selection bar.
Since cabbage whites can have up to three broods in a good summer, it is important to install the netting in the spring and leave it in place until autumn. Even under netting however, regular inspection of leaves is essential. Although laborious, picking eggs and larvae by hand from the plants works well. Because small White larvae are well-camouflaged, be sure to look under leaves’ ribs, where they frequently hide. It can be simpler to identify them if you grow red-leaved varieties of cabbage and other brassicas.
Encouragement of natural predators is a great way to control pest populations, as any organic gardener knows (and saves you from having to perform grisly executions personally) However, cabbage white larvae have a trick up their sleeve: most predators find them repulsive because of the mustard oil they store in their bodies from the food plant. However, some birds will still eat them, so it’s worthwhile to have nest boxes and feeders in your garden to attract insectivorous birds like skylarks, goldfinches, and house sparrows.
The parasitic wasp Apanteles glomeratus can feed on large white cabbageworms. Its larvae eat the caterpillar from the inside out, taking care to avoid the host’s vital organs so the host can grow to full size. It may be worthwhile to move any dead caterpillars with yellow cocoons next to them among your brassicas so that the parasites will attack subsequent generations.
It’s a good idea to check these areas and remove any larvae you find because once fully grown, they will move away from the food plants and make their way to somewhere sheltered, like a fence, shed wall, or tree trunk. There, they will pupate for about two weeks in the summer or eight weeks if they are overwintering.
Considering the destruction done to my nasturtiums, it surprised me that I didn’t find even one pupa over the winter. However, spiders seemed to feast on the larvae last year, and this year I’ve also seen butterflies entangled in their webs.
I’m planting nasturtiums again, even though I know they will probably be completely destroyed. Hopefully, their presence will deter butterflies from trying to crawl under my netting so I can harvest some nice broccoli later this summer!
By Ann Marie Hendry.
The orange tip butterfly, which emerges in the spring, is one that is frequently confused with a cabbage white. The lovely cuckoo flower, found in meadows, serves as the orange tip caterpillar’s food source. The female of this species has plain black and white wings, but the male has bright orange tips, which are the source of the species’ name.
Moths and butterflies are a vital food source for bats. Many other animals, including other insects, spiders, frogs, birds, toads, lizards, and mammals like bats and hedgehogs, eat moths, butterflies, and caterpillars. The large cabbage white butterflies are poisonous to most birds, which may surprise you. As a result, robins, blackbirds, and other birds avoid them, making the parasitic wasp a crucial predator.
The less well-known carnivorous spiked shieldbug is another predator of the cabbage white caterpillar. It eats its victims by drawing blood from their bodies through a spiked mouthpart.
While there are only about 59 species of butterflies in the UK, there are an astounding 2500 species of moths, with hawk moths being some of the largest.
Instead of using harsh pesticides and other chemicals that damage wildlife and the soil, organic and agro-ecological farmers and gardeners build healthy soil, create wildlife corridors and habitats for nature, and support a variety of predators that prey on pests, including parasitic wasps that search for and lay their eggs on the cabbage white caterpillar, their main prey. When the wasp larvae hatch, they feed inside the caterpillar, avoiding its vital organs, until they are ready to transform into adult wasps and pupate. Since the predated caterpillar will never mature into a butterfly, things will remain balanced.
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.
The Small White butterfly has been introduced to North America, Australia, and New Zealand (sorry, guys!), where it is commonly referred to as the imported cabbageworm. Both butterflies are widely distributed throughout Britain and Europe. If it’s any comfort, I learned that the Small White is not as voracious a feeder as the Large White when I saw six healthy nasturtiums 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 theyre around in fewer numbers, a handful of larvae can still do serious damage to your crop.
FAQ
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