In balance: the cabbage white butterfly

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.

Cabbage white are considered by gardeners pests of brassica, or the cabbage/mustard family.

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 there’s 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 world’s 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.