The white cabbage butterfly is a pretty little thing, but it can be very harmful for your garden.
Heading into the colder months of the year, you may spot small white butterflies weaving their way through your garden. While they are quite nice to spot, as is any butterfly, a white cabbage butterfly could mean your garden is at risk of damage.
It actually comes down to two different species, a moth and a butterfly, that are very similar in their looks and eating habits. They are both introduced insects, and are major pests for plants in the Brassicaceae family. It is not uncommon for both pests to occur on the same plants at this time. These two are both named after the food that they love to eat:
- Cabbage Moth (Plutella xylostella – species, Plutellidae – family)
- Cabbage White Butterfly (Pieris rapae – species, Pieridae – family)
These two winged wonders usually appear just in time for the winter vegetables to sprout. However, it’s not the fully grown butterflies you have to worry about, but the caterpillar it is beforehand. Let’s go through how to spot which one is which, and how to prevent them from ruining your garden.
What is a white cabbage butterfly?
Cabbage White Butterflies (Pieris rapae) have creamy white wings that are whiter on the upper sides and more yellow underneath. Their tell-tale sign is a black spot (or two black spots for females) on their forewing. Their wingspan can grow up to 45mm.
The eggs of this insect are pale yellow, oval and have distinct longitudinal ridges, while larvae are green in colour, with faint yellow stripes down the back and along each side.
What is a white cabbage moth?
The white cabbage moth (Plutella xylostella) is also known by another common name, the ‘Diamondback Moth’. This is because of its distinct diamond pattern on their wings. This is what makes it easy to tell the two insects apart from each other.
Cabbage moth eggs are also similar to that of cabbage white butterfly, with pale yellow, oval eggs. Cabbage moth larvae however, have certain characteristics, like curling into a horseshoe shape or hanging from a silken thread, which can help you identify it.
Which plants are impacted by white cabbage moths and cabbage butterflies?
Plants in the Brassicaceae family including:
- Broccoli
- Cabbage
- Cauliflower
- Canola
- Radishes
- Turnips
- Stock
- Alyssum
- Nasturtium
- Wild Mustard
- Wild Radish
- Shepherd’s Purse
How to protect your winter vegies from cabbage moths
Just as these two insects are slightly different in looks, they are also different in the way that they eat up your plants. Cabbage white butterfly larvae will initially chew small holes in leaves before growing larger and damaging more of the plant.
They tend to create irregular holes in outer leaves and the heads of broccoli and cauliflower, and if there are many of them, they can even strip the leaves back to the main vein.
Cabbage moth larvae, on the other hand, will feed leaves as soon as they hatch. They usually like to infest brassica head more than the butterfly larvae does as well.
Although different in damage, the prevention for these insects is the same, and mainly involves keeping a close eye on your broccoli, cauliflower and cabbage. Other pest control steps you can take include:
- Killing any weeds: removing brassica weeds like wild mustard and shepherd’s purse means that there’s a less likely chance of a cabbage moth or cabbage butterfly infestation in your vegie patch. This can be done simply by pulling weeds or spraying a general weedkiller.
- Setting up netting: using a fine mesh or netting over your plants that can be affected by cabbage moth or cabbage butterfly means that these insects will not even get the chance to lay their eggs.
- Remove plant material: caterpillars love any leftovers, and thrive in messy garden beds. A great way to reduce cabbage moth and butterfly infestation is by simply keeping everything clean and tidy.
- Remove caterpillars by hand: of course, if eggs have been laid and not removed in time, the best thing to do is get down and dirty and remove the caterpillars yourself.
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