There is another species of cabbage white butterfly, called the large cabbage white butterfly (Pieris brassicae). It is difficult to distinguish between them as the adults are very similar but their larvae are very different. The caterpillars of Pieris brassicae are black with prominent yellow stripes along the length of the body. They are spikier than the small white butterfly larvae and feed in clusters. There is usually more of them and therefore tend to do more damage.The caterpillars of Pieris rapae have short hairs all over and are pale blue-green with thin yellow dashes along the length of their bodies. They are more solitary than the large white and there tends to be less of them.
Adult butterflies have white wings with black tips. Males’ wings have one black dot and the females’ have two.
The eggs are pale yellow to yellow and look like upside down urns; elongated with vertical ridges.
Adult size: 50-55mm wingspan
Out and about
They are active in spring when larvae (caterpillars) have lovely new growth to feed on and then, of course, later when the brassicas (cabbages and broccoli) are growing. They seem to favour more temperate regions but will tolerate slightly warmer and cooler climates. Originating in Europe is has been introduced into China, North America, Australia and New Zealand.
Reproduction and Life cycle
The female lays single eggs on the underside of leaves. Usually two generations are produced over the warmer months but if conditions are right there could be another lot. The eggs hatch in about 7 days and take another three to four weeks to reach adulthood.
To deter
The white cabbage butterfly is territorial it is possible to trick them into thinking there are already butterflies on your plants.
- Place eggshells with the white side up around and on the plants
- Cut out butterfly shapes from white plastic and suspend them over the plants
- place netting over plants so that the butterfly can’t get to them
- Plant land cress (Barbarea vulgaris)- attracts the butterfly to lay eggs and kills the larvae when they eat it.
To control
To control caterpillars
- Bacillus thuringiensis (Bt) is available commercially. It is a bacterium which attacks the digestive system of caterpillars. It only affects caterpillars and is therefore harmless to other animals.
- Spinosad is another bacterium available commercially that also kills caterpillar eggs.
- Sift flour over leaves will kill caterpillars as it blocks their breathing pores and they suffocate.
- Sprinkle pepper on the leaves in the morning when they are still moist will deter
- A garlic tea laced with pepper as a spray will help
- Molasses spray
- Neem oil spray
- Place cardboard collars around seedlings as a physical barrier for cutworm
- Collect dead caterpillars after treating and blend them up then use this as a spray on other live caterpillars
- Pieces of raw potato and carrot will trap wire worm
- Keeping area clear from weeds will help with cutworm in particular as this eliminates areas for them to shelter
- Lightly digging the soil surface can disturb pupae and expose the cutworms for birds and other predators
Plants to repel
Plants to repel
Artimisias (daisy family) / Chamomile / Dill / Hyssop / Lad’s love / Mint / Oregano Rosemary / Sage / Spearmint / Tansy / Thyme / Southernwood / Wormwood
A border of these mixed together would be helpful
Plants to attract
Predators
Birds / Spiders / Predatory bugs / Beetles
Predators of the larvae are the same as for any caterpillar
Some ground beetles / Lacewings / Tachinid flies / Parasitoid wasps / Assassin bugs
Why they are a Pest
The white butterfly lays eggs on vegetables and their larvae love to eat the leaves. Although there doesn’t seem to be a lot of eggs or caterpillars around their voracious appetites cause a fair bit of damage to the leaves of crops if not dealt with early enough. They particularly like broccoli and cabbages.
