Cabbage White Butterflies

Dirty Nails has some fine, healthy young specimens of purple sprouting broccoli. They were planted out at the end of May and now stand around a foot (30 cm) in height with thick stems and juicy, broad leaves. The pigeons have been deterred by lines of string crisscrossing over them between sticks and, dangling on canes, takeaway cartons that move and make a noise in the breeze. Rabbits are having an occasional nibble, but mercifully not doing any serious damage yet.

The big thing that Dirty Nails looks out for on all his brassicas from now onwards is butterfly damage. Two butterflies lay their eggs on purple sprouting and other members of the cabbage tribe: the large and small white. They are on the wing now, sniffing out their favourite food-plants.

The large white lays its tiny yellow eggs in clusters that are easy to detect on the underside of leaves. When the caterpillars hatch they eat their egg-cases and then start tucking into the leaf. At this stage they tend to feed together. As they grow they quickly spread out over the whole plant and can devastate it to the point of being a skeleton. The caterpillars are yellow and black.

The small white lays its minute eggs singly on the underside of the leaf. Its caterpillar is small and green. It takes some looking for. They are a particular problem on cabbages because they start feeding at the heart and then eat their way outwards.

Dirty Nails makes time at least twice a week to have a thorough hands-on check of his brassicas. He gently rubs out patches of eggs with his thumb, but will not squash the caterpillars once they have hatched. Instead, he uses a fine paintbrush to remove them into a jar and relocates them elsewhere in the garden, onto nasturtiums which they also love. He grows nasturtiums specifically for this job. This is a time-consuming task but it gives Dirty Nails real pleasure to be outside looking for caterpillars and listening to birdsong on a peaceful summer evening.

Natural History In The Garden: Blackbirds

Keep an eye out for blackbirds congregating on the lawn this month, in groups of half a dozen or more. Members of the thrush family, the handsome males are glossy black with bright orange-yellow beaks and eye rings. Females are a duller brown.

Blackbirds like to hop, skip and jump over the turf, watching and listening for invertebrate movement. They will stand still and cock their heads, keeping a keen ear out for the faint rustle of earthworm activity, before pouncing and stabbing the ground, then tugging out a tasty morsel. A blackbird whose beak is dripping full with worms may well be feeding a newly fledged youngster nearby.

Vegetable Snippets: Large White Life Cycle

Clouds of white butterflies mixing together above the cabbage patch, rising and falling in delicate dance, like bubbles of fizz in a glass of lemonade, used to be a far more common sight in our towns and gardens before the widespread use of insecticides put paid to vast numbers of these infuriating but beautiful insects. In the vicinity of suitable food-plants where chemicals are shunned or not used at all, the wildlife-friendly grower may be treated to the spectacle of a gathered knot or three of these charming customers, bobbing and weaving as they pass across his little piece of heaven, doing what they’ve always done, lending a delicious ‘scene from yesteryear’ taste to the garden landscape.

They are amazing creatures, make no mistake. Large whites develop from egg to adult, experiencing a change known as ‘complete metamorphosis’. On the wing in April and May, having survived the winter as a chrysalis tucked away somewhere sheltered and safe, they mate. She lays batches of yellow eggs on the underside of brassica leaves, and in two weeks a mass of tiny caterpillars emerge with only one thing on their minds - to eat! This they do, non-stop, through June, growing quite large and distinctive.

When ready, the satiated caterpillars sneak away to hole-up in a handy crevice or woody cabbage stalk, to pupate. Forming a chrysalis to protect themselves during this most incredible transformation, they completely rearrange their bodies both inside and out, and emerge in July as the familiar cabbage white to wreak more havoc on the veg plot. A second generation of youngsters may prove more damaging than the first, and this lot generally over-winter in a chrysalis to commence the process again when early-summer next comes around.

Natural predators of the large white include starlings, which scoff lots of these pests as caterpillars, and wasps which snatch them as food for their grubs. Spiders also do a fine job of snaring the adults, paralysing them, and then sucking their bodily juices dry.