Cabbage Butterflies in your Vegetable Patch
Written by Helen Holman
Have you noticed holes appearing in the leaves in your vegetable patch? This is most likely being caused by a green caterpillar which is the larvae of the White Cabbage Butterfly, a not so popular garden pest.
While this unsightly damage upsets the aesthetics of your garden, it also means your yield is lower as you’re sharing your greens with these ravenous critters!
The White Cabbage Butterfly is about 40mm in size with white wings that have a black corner spot. You may have seen them fluttering around your yard, they are quite pretty to look at and the butterfly itself is not harmful to your veggies – it’s their larvae that do all the damage. They are attracted to your brassicas, which include plants of the cabbage and mustard family such as pak choi, turnips, broccoli, kohlrabi and brussel sprouts just to name a few. The butterfly lays its eggs on the underside of the leaves, and once hatched the caterpillars go straight to work eating your greens.
Here are a few tips on how to organically manage these pests in your garden.
Netting your beds
One of the easiest methods is preventative action – before the butterflies have a chance to lay their eggs – restrict their access. You can do this by constructing a frame and netting your garden beds, this allows sunlight and water into your garden but restricts the butterflies from accessing your veggies.
Constructing a frame is easy – you can either purchase pre-made garden frames or you can just as easily make your own. An easy DIY frame can be constructed with a few wooden garden stakes, and some lengths of polypipe. Hammer a stake into the ground on each corner of your garden bed. Measure and cut two lengths of poly pipe that can be threaded over the top of the ends of two stakes, to form two large arches at each end of the bed – then simply throw the net over.
There are lots of different nets available on the market – the best variety have finer holes and are bird friendly.
Cabbage butterfly caterpillars are easy to identify, they are small and green, and they can be found on the leaves that have visible damage including holes and rough edges. Most typically they are found on the underside of the leaf. Simply remove by pulling the caterpillar off and discarding in your compost bin, or feeding to your chickens.
Cabbage Butterfly eggs are an oval shape and are small and pale in colour. They are most commonly laid directly onto on the underside of leaves, and can be found by turning and inspecting the leaves of your brassicas. Eggs can be picked off or squished before they hatch.
Planting sacrificial decoy plants will help in the deterrence of Cabbage Butterflies from your brassicas. Nasturtiums are a great plant that grows voraciously that can be used to attract the butterflies, and once caterpillars emerge the entire plant can be removed and discarded.
Some strong-smelling herbs such as rosemary, sage and lavender can be planted among your veggies to deter the butterflies from laying their eggs on your brassicas.
Butterfly-shaped decoys can discourage butterflies from settling on your veggies. They are territorial creatures and avoid laying their eggs in the vicinity of other butterflies, so a decoy butterfly can be enough to send them elsewhere and away from your garden.
A more targeted method for pest management is using a spray. Eco Oil and Eco Neem are both a great organic and environmentally friendly solution for managing Cabbage Butterfly larvae. These both use an oil to target the caterpillar, and are veggie-safe with no withholding period.
It’s important to remember that once you have spotted Cabbage Butterflies in your garden to try one or more of the steps above remain in top of their population control. If left to their own devices their larvae can quickly form an army that will turn all your brassicas into skeletons!