Cabbage white butterfly: detection & control

Is the caterpillar of the large cabbage white poisonous? What are the ways to treat this pest? Learn everything you need to know about the cabbage white butterfly in this article.

The diet of the cabbage white (also called large cabbage white) consists primarily of the leaves of headed cabbage, cauliflower, green cabbage, kohlrabi and various other cabbage varieties that we prefer to end up on our own plates. Although the butterfly is beautiful, do not be fooled by its looks, it really is not a pleasant visitor in the vegetable garden. This article contains detailed information on cabbage white butterflies for you to effectively prevent and combat cabbage white infestation.

For a start we will have a closer look at the cabbage moth in general: What they look like, how they develop and if they are poisonous. Then, we will go into detail about effective treatment measures such as household remedies, chemical products and natural methods.

Cabbage white butterfly: profile

The following table describes the different stages of cabbage white butterfly life cycle and other cabbage white butterfly facts such as, its appearance and the damage pattern.

Are the cabbage caterpillars poisonous?

When munching on cabbage plants, the cabbage white caterpillars absorb various substances, such as mustard oil glycosides, which are poorly tolerated by humans. The caterpillar’s metabolic processes however break the substances down transforming them into toxic substances such as isothiocyanates. They can irritate mucous membranes and have negative effects on the production of thyroid hormones. Due to the isothiocyanates the caterpillars are also inedible for many predators. The caterpillars themselves are immune to the substances. For humans, the substances are only toxic in large amounts. Touching (and possibly even eating) the cabbage white caterpillars is as harmless as eating cabbage. Even eating cabbage, humans produce various slightly toxic metabolic degradation products themselves.

Tip: What is the difference between the large cabbage white (Pieris brassicae) and small cabbage white butterfly (Pieris rapae)? At first glance they look very similar. The main differences lie in their habitat, diet and feeding behaviour. Unlike its larger relative, the small white butterfly eats through the leaves and reaches the inner core of the plants. Among cabbages it devours various other crucifers, leeks, capers, iberis and rocket. Due to the broader food spectrum, small cabbage white is somewhat more widespread than the large white butterfly, whose diet is more restricted, sticking strictly to cabbage plants. However, since damage and control are largely the same with both species, no distinction is made in the following.

Development of the cabbage white butterfly

In temperate climate, two to four generations occur every year, the first butterflies fly between April and June, the last in October at the latest. After laying the eggs, it takes about 14 days for the caterpillars to hatch. The small caterpillars then make their way over to the leaves of the forage plant. The main damage usually occurs in June and July. After three to four weeks of eating, the caterpillars pupate. The last generation hibernates in this form.

Preventing a cabbage white infestation

An infestation can be prevented by taking some simple precautionary measures:

1. Plant mixed crops instead of one variety of cabbage (which is more likely to be infested).
2. Maintain crop rotation in your garden.
3. Plants with a strong scent drive pests (including the cabbage white) away from the garden bed. Thyme, mugwort, aniseed, tansy, sage, peppermint, tomatoes and extracts from these plants are great pest repellents.
4. Supporting native wildlife reduces the likelihood of a pest infestation. Many songbirds prey on the butterflies, while native ichneumon wasps parasitize on the caterpillars and eggs.
5. Look for eggs under the leaves of the potential forage plants as soon as you spot the white butterflies in your garden. Early recognition will prevent a heavy infestation.
6. Collecting eggs and caterpillars manually can be a simple treatment if the infestation is small.
7. Protect the vegetables with nets before the butterflies first fly in spring. The size of the mesh should not exceed two millimetres and the nets should not have any holes.

Tip: If you missed the time of the first flight of the butterflies, you can still use the nets to partially shield the plants. But, additionally, collect any eggs or caterpillars and also use other methods of treatment.

Getting rid of cabbage white butterflies

You can combat the cabbage white butterfly with household, chemical or natural products.

Natural control of cabbage white butterflies

There are two possible ways to treat cabbage white butterflies naturally. One way of treatment is using beneficial organisms; another possibility entails the bacterium Bacillus thuringiensis. As a general rule, the earlier the methods of control are implemented, the less damage is done to your plants. And the longer you wait the more the caterpillars eat themselves into the inner part of the cabbage where you cannot reach them with any sort of pest management. Therefore, it is vital to start treatment immediately.

There are several species of beneficial insects that can be used to combat cabbage butterflies. The white butterfly parasite Cotesia glomerata preys on caterpillars, preferably of the Pieris brassicae species as it is specialised on large cabbage white. The small cabbage white butterfly has an arch nemesis of its own: Cotesia rubecula. Both of the parasitic species are used by professionals to control cabbage white butterflies but are unfortunately hardly available to private users. Nevertheless, they are insects native to Europe attracted by the smell of cabbage. Therefore, by making your garden as insect-friendly as possible, you will promote beneficial organisms that will help you in the battle against pests.

Then there are beneficial insects which instead of targeting caterpillars parasite on the eggs such as the ichneumon wasps of the genus Trichogramma. They for example prey on cabbage butterfly eggs and they are commercially available. The Trichogramma species lay their own eggs close to those of the butterflies. The wasp larvae hatch from their eggs, then feed on the contents of the butterfly eggs.

Note: Unfortunately, the use of parasitic wasps in the field is often not efficient. The small wasps migrate, are driven away by strong winds or eaten by other insects and birds. However, using them in greenhouses has proven to be significantly more effective.

Insecticides based on Bacillus thuringiensis are impressive natural agents to use in the field. The bacterium comes in a water-soluble powder that upon mixing with water can be used as a spray. The spray is applied to the forage plants of the cabbage white. Repeat the treatment if the plants grow or it rains. So what does this product do exactly? The bacterial spores are absorbed by the caterpillars when they feed. The intestines of the butterflies contain certain enzymes that unfold toxic abilities of the bacterium. Importantly, the bacterium only works against cabbage white butterflies, and therefore, other non-target species are protected.

Household remedies against cabbage white butterflies

Unfortunately, in case of a serious infestation, household remedies are not enough to salvage your cabbage harvest. For this reason, we recommend using preventative measures at an early stage, as described above. Since butterflies and caterpillars occur during the entire growing season, you can protect your plants with preventative and natural methods described above throughout the whole cultivation period.