Cabbage white butterfly: detection & control
Is the caterpillar of the large cabbage white poisonous? What are the ways to treat this pest? Find all the answers in this article.
The diet of the cabbage white (also large cabbage white) butterfly 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 plates. Although the butterfly is beautiful, do not be fooled by its looks, it really is not a pleasant visitor in the vegetable garden. The insatiable caterpillars will easily decimate whole garden beds full of cabbage, so an effective remedy is frequently sought after. We have compiled all the important information on cabbage white butterflies for you, so that nothing stands in the way of effective prevention and control.
Cabbage white butterfly
First, we will get to know the butterfly a little closer, so that it is clear what this species looks like. After that, the article provides information on the development and toxicity of the cabbage white. Then, we will go into detail about effective treatment measures including using household remedies, chemical products and natural methods.
What does cabbage white butterfly look like?
The following table describes the different stages of development of the cabbage white, its appearance and the damage pattern.
|Taxonomy||Family Pieridae, Genus Pieris|
|Origin||North Africa to Northern Europe|
|Forage plants||Various cruciferous plants (Brassicaceae), which include our cultivated cabbage varieties, rarely other plants|
|Eggs||Bright yellow, on the underside of the leaves of the forage plants|
|Caterpillars||Green and yellow, with patterns of black spots; body is short and hairy, not more than 4 cm long|
|Butterflies||White and light yellow in colour, wingspan maximum 6.5 cm, the tip of the fore wings has a black mark; diurnal, pollinate various wild and garden plants|
|Pattern of damage||Plant corrosion occurs; in case of strong infestation, skeletonization of whole leaves|
|Pupae||Attached to the stems or leaves of plants|
Are the caterpillars poisonous?
When eating cabbage plants, the caterpillars of the cabbage white plant absorb various substances that are poorly tolerated by humans in large quantities, such as mustard oil glycosides. These are digested during the metabolic processes of the caterpillars and toxic substances such as isothiocyanates are produced. These irritate mucous membranes and have negative effects on the production of thyroid hormones. The caterpillars of the cabbage white butterflies contain these isothiocyanates, making them inedible for many predators. The caterpillars themselves are immune to these substances. For humans, these substances are only toxic in large amounts. Touching (and possibly even eating) the caterpillars of the cabbage white is just as harmless as eating cabbage. Because even when we eat cabbage, various slightly toxic products occur when they are degraded by our metabolic processes.
Tip: What is the difference between the large cabbage white and small cabbage white butterfly? The large cabbage white butterfly (Pieris brassicae) and the small cabbage white butterfly (Pieris rapae) are at a first glance very similar. The main differences lie in their habitat, diet and feeding behaviour. Unlike its larger relative, the small cabbage white eats through cabbages and reaches the inner core of the plants. Other than on cabbage plants, it prefers to forage on various other crucifers, leeks, capers, iberis and rocket. Due to the broader food spectrum, the small cabbage white butterfly is somewhat more widespread than the large cabbage white butterfly, whose diet is more restricted. The large white butterfly sticks more strictly to cabbage plants. However, since damage and control are largely the same with both species, no distinction is made between them in the following.
Development of the cabbage white butterfly
In temperate climate zones, 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:
- Plant mixed crops instead of one variety of cabbage (which is more likely to be infested).
- Maintain crop rotation in your garden.
- 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.
- 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.
- 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.
- Collecting eggs and caterpillars manually can be a simple treatment if the infestation is small.
- 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; other possibility entails the bacterium Bacillus thuringiensis. As a general rule, the earlier the methods of control are implemented, the less damage will be done to your plants. A possible additional obstacle is that the caterpillars of the small cabbage white also eat their way inside the cabbage heads and from a certain point are no longer accessible. Therefore, it is vital to start treatment immediately.
There are several species of beneficial insects, that can be used in the battle against cabbage butterflies. First, the white butterfly parasite Cotesia glomerate preys on the caterpillars of the large cabbage white. This predatory insect prefers the species Pieris brassicae above all else. 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. However, both of the beneficial insects are native to Europe and are 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.
The ichneumon wasps of the genus Trichogramma target the eggs of the both cabbage white species. Various species of the predatory wasps are commercially available. The Trichogramma species lay their own eggs close to those of the butterflies. The wasp larvae, that hatch from their eggs, then feed on the contents of 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. If the plants grow or it rains, the application should be repeated. And how exactly do these products work? The bacterial spores are absorbed by the caterpillars when they feed. The intestines of the butterflies contain certain enzymes, that unfold the toxic abilities of the bacterium. Importantly, the bacterium only works against cabbage white butterfly, and therefore, other non-target species are protected.
Chemical control of cabbage white butterflies
The gardening market offers various chemical products that are recommended to use against cabbage white in the home garden. Many commercially available agents use the active substance azadirachtin, which comes from the neem tree and is harmful to various insects – most of which are beneficial insects. Some products contain pyrethrin that is also detrimental to beneficial species. Other products, which are also often approved for home gardens, contain cyhalothrin which is deadly to bees. We assume that no responsible garden owner wants to pollute their garden with any of these toxins, so we will stop right here.
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 the preventative and natural methods described above throughout the whole cultivation period.