Pieris brassicae, commonly called the large white or large cabbage white butterfly, is one of the most widespread and damaging pests of brassica crops across Europe, Asia, and parts of North Africa. Adults are easy to spot in flight thanks to their broad, creamy-white wings tipped with black, and their gregarious caterpillars can strip a cabbage plant to bare ribs within days. Despite its familiarity, the species has a surprisingly complex biology involving seasonal migration, temperature-sensitive diapause, and chemical defenses that make it harder to control than many gardeners expect.
How to Tell the Large White From the Small White
The large white is frequently confused with its close relative, Pieris rapae, the small cabbage white. The most reliable visual difference is size: large whites have a wingspan of roughly 55 to 65 mm, while small whites typically span about 40 to 50 mm. Beyond wingspan, the black markings at the wing tips of P. brassicae are heavier and extend further along the forewing margin. Females of both species carry two dark spots on each forewing, but in the large white these spots are bolder and more conspicuous. Males of P. brassicae have only faint spots or none at all, while the wing-tip markings remain distinctive.
At the chemical level, the two species differ in their mating signals. Male large whites produce a wing pheromone called brassicalactone, a macrolide compound that females detect with their antennae. Small whites, by contrast, use a related but structurally smaller compound called ferrulactone. When researchers applied each species’ pheromone mixture to freshly emerged males, mating success increased compared to untreated males, confirming that the compounds serve as genuine aphrodisiacs rather than mere chemical curiosities.1Chembiochem. Aphrodisiac pheromones from the wings of the small cabbage white and large cabbage white butterflies, Pieris rapae and Pieris brassicae These chemical differences help explain why the two species do not interbreed even when they share the same cabbage patch.
Eggs, Larvae, and Pupae
Female large whites lay their eggs in clusters of 20 to 100 on the underside of brassica leaves, a habit that immediately distinguishes them from small whites, which lay single eggs. The pale yellow, ribbed eggs darken slightly before hatching, usually within a week under warm summer conditions. Temperature plays a decisive role in how quickly every stage develops. Research on populations in Kashmir found that eggs need a minimum temperature of about 10°C to develop at all, while larvae can grow at temperatures as low as 5°C. Pupae require at least about 8°C.2Crop Protection. Temperature-driven development, survival, and phenology modelling of Pieris brassicae in Kashmir Valley: implications for pest management That difference matters practically: early-season caterpillars can keep feeding during cool spells that would stall egg development entirely.
Young larvae are pale greenish-yellow and gregarious, feeding side by side in conspicuous groups. As they grow through five instars, they become more boldly patterned with black spots and yellow stripes. This coloring is a warning signal. When disturbed by a predator or parasitoid, the caterpillars regurgitate semi-digested plant material loaded with glucosinolates, the pungent defensive chemicals found in brassica leaves.3PubMed. Growth and reproductive costs of larval defence in the aposematic lepidopteran Pieris brassicae This regurgitation response is quick and effective enough to deter many generalist predators, though it comes at a metabolic cost to the caterpillar.
Fully grown larvae leave the host plant to pupate, often on walls, fences, or sheltered overhangs some distance from where they were feeding. The chrysalis is angular and mottled gray-green, anchored with a silk girdle. Whether the pupa enters dormancy or produces an adult within a few weeks depends on the day length the caterpillar experienced while growing.
Diapause, Dormancy, and How Day Length Controls Generations
Most butterfly guides describe diapause as a simple switch: short days trigger winter dormancy, long days keep the insect developing. The large white does not work that cleanly. Researchers found that P. brassicae can measure fine differences in night length across a broad range, roughly 5 to 13 hours of darkness. Longer nights push a higher proportion of individuals into diapause, but even relatively long summer days can tip some caterpillars toward dormancy, and relatively short autumn days do not guarantee that every individual will diapause.4Journal of Insect Physiology. Quantitative measurement of photoperiods and its significance for the induction of diapause in Pieris brassicae (Lepidoptera, Pieridae) This graded response helps the species hedge its bets in unpredictable climates.
Once in pupal diapause, the insect must survive months of cold. Overwintering pupae accumulate sorbitol, a sugar alcohol that acts as a cryoprotectant. Concentrations build from autumn through about December and then decline through spring. During the peak sorbitol period, pupae tolerate cold well despite never becoming truly freeze-tolerant; their supercooling point hovers around minus 23 to minus 25°C all winter.5Physiological Entomology. Physiological aspects of diapause and cold tolerance during overwintering in Pieris brassicae The practical upshot is that P. brassicae pupae can survive harsh European winters tucked against a garden wall, emerging the following spring ready to breed.
In the warmest parts of its range, the species faces the opposite problem. Populations in southwestern Iberia, south of the Pyrenees, undergo a summer diapause or aestivation, pausing development during the hottest, driest months when host plants are scarce. This summer dormancy appears geographically stable and does not occur in northern European populations.6European Journal of Entomology. The occurrence of summer diapause in the large white butterfly Pieris brassicae (Lepidoptera: Pieridae): A geographical perspective
Migration
Large whites are genuine migrants, not just local fliers blown off course by wind. In northern Europe, populations are typically bivoltine, producing two generations per year. Studies comparing populations across the continent found that the developmental fate of the caterpillars determines flight direction. In northern Germany, caterpillars that entered pupal diapause produced adults that flew northward the following spring, while non-diapausing pupae from the summer generation gave rise to adults that migrated southward. In multivoltine southern populations, the pattern was different: the second generation maintained the same flight direction as the overwintered generation.7Ecological Entomology. Geographic comparison of seasonal migration events of the large white butterfly, Pieris brassicae
A particularly interesting case was found along the northern coast of Spain, where the sea acts as a barrier that seems to force an adapted migration pattern: the spring generation flies southeastward, and the summer generation reverses course to the northeast.7Ecological Entomology. Geographic comparison of seasonal migration events of the large white butterfly, Pieris brassicae These mass movements can bring sudden influxes of egg-laying females into regions that had few butterflies earlier in the season, which is one reason “cabbage white plagues” seem to appear overnight in some years.
Host Plants and Where Females Choose to Lay
The large white attacks virtually all cultivated brassicas: cabbage, cauliflower, broccoli, Brussels sprouts, kale, and kohlrabi. It also feeds on nasturtiums, wild mustards, and other plants in the family Brassicaceae. Females tend to prefer younger, more vigorous plants for egg-laying, but this preference does not always translate into better performance for the resulting caterpillars. Research on Brussels sprout and a wild relative found that differences in plant chemistry, particularly glucosinolates, sugars, and amino acids, were more pronounced between tissue types (leaves versus flowers) than between younger and older developmental stages of the same plant.8PubMed Central. Oviposition Preference for Young Plants by the Large Cabbage Butterfly (Pieris brassicae) Does not Strongly Correlate with Caterpillar Performance In other words, a female laying on a young plant is not necessarily giving her offspring a nutritional advantage, and the mismatch between oviposition preference and larval success is an ongoing puzzle in the ecology of this species.
From a gardener’s standpoint, the takeaway is simple: any brassica in your plot, young or old, is a potential target. Monitoring should cover the whole crop, not just the newest transplants.
Biological Control and Its Limits
The parasitoid wasp Cotesia glomerata is probably the most widely discussed natural enemy of cabbage white caterpillars, and gardeners who spot clusters of small yellow cocoons on or near dead caterpillars are seeing its handiwork. But the relationship between C. glomerata and P. brassicae is more complicated than the textbook version suggests. In Japan, where P. brassicae is a relatively recent arrival and the local wasp populations are adapted to parasitizing the small white, researchers found that C. glomerata females actively avoided large white caterpillars. Even when wasps inserted their ovipositors into P. brassicae larvae, none successfully laid eggs.9Ecological Research. Response of the wasp (Cotesia glomerata) to larvae of the large white butterfly (Pieris brassicae) The gregarious feeding and vigorous regurgitation defense of large white caterpillars likely contribute to this avoidance.
Even where C. glomerata does successfully parasitize P. brassicae, the benefit to the crop is not always straightforward. Parasitized caterpillars continue feeding throughout most of their development; the wasp larvae consume their host from the inside but do not kill it quickly. Testing whether parasitism actually reduces leaf damage, researchers found no clear reduction in herbivory from parasitized versus unparasitized caterpillars.10Journal of Applied Entomology. Parasitism of the herbivore Pieris brassicae L. (Lep., Pieridae) by Cotesia glomerata L. (Hym., Braconidae) does not benefit the host plant by reduction of herbivory Parasitized caterpillars still chew through plenty of leaf before the wasp larvae emerge. For gardeners counting on wasps alone to save the cabbage harvest, this is a reality check.
Another biological option targets the pupal stage. The pupal parasitoid Pteromalus puparum lays its eggs inside the chrysalis, and the emerging wasps kill the pupa before the butterfly can develop. This parasitoid was mass-reared and released as part of the New Zealand eradication campaign (discussed below) to attack pupae that were difficult to find and remove manually.11New Zealand Plant Protection. Mass rearing Pteromalus puparum on Pieris rapae to assist eradication of Pieris brassicae from New Zealand
Microbial and Biorational Options
Bacillus thuringiensis (Bt) is the most common microbial insecticide used against caterpillars, and it works well against large whites. Interestingly, naturally occurring Bt bacteria already living on brassica leaf surfaces can cause significant mortality on their own. When newly hatched P. brassicae larvae fed on Chinese cabbage leaves colonized by wild Bt, about 35% of the caterpillars died within 72 hours. The bacteria then multiplied roughly 50-fold in the cadavers, potentially creating a reservoir for further infection of other caterpillars nearby.12Journal of Invertebrate Pathology. Effect of Bacillus thuringiensis naturally colonising Brassica campestris var. chinensis leaves on neonate larvae of Pieris brassicae Commercial Bt sprays deliver much higher doses than natural leaf populations, so their kill rates are correspondingly greater. Timing the spray to hit young larvae just after hatching is the key to getting good results, since older caterpillars eat less leaf surface relative to their body mass and may ingest a sublethal dose.
Neem-based products offer another biorational approach. Laboratory and field trials have tested several neem formulations against P. brassicae and found that they work on multiple fronts: females lay fewer eggs on treated leaves, larvae that do hatch stop feeding and often drop off the plant, and direct contact reduces egg survival. In one set of laboratory trials, nine-day larval survival on neem-treated leaves ranged from roughly 18% to 51% depending on the formulation, compared to untreated controls.13Crop Protection. Toxic effects of neem-based insecticides on Pieris brassicae (Linn.) Field trials have echoed these results, with neem seed oil reducing larval populations more effectively than some synthetic pyrethroids.14Advances in Entomology. Comparison of Efficacy of Synthetic Pesticides with Botanical Extracts under Field Condition on Cabbage White Butterfly (Pieris brassicae) Because neem acts partly by deterring egg-laying, it is most useful when applied before butterflies arrive in large numbers rather than after the damage has started.
Granulosis viruses specific to P. brassicae (PbGV) represent yet another avenue. These naturally occurring baculoviruses infect and kill caterpillars without affecting other organisms, and laboratory bioassays have confirmed high virulence against second-instar larvae. Adding phagostimulants, substances that encourage feeding, to the virus formulation can improve uptake by the caterpillars. Early field results suggest that PbGV has potential as a sustainable alternative to chemical sprays, though it has not yet been commercialized at scale.15Egyptian Journal of Biological Pest Control. Synergistic effect of naturally occurring Granulosis virus isolates (PbGV) with phagostimulants against the cabbage butterfly, Pieris brassicae (L.) for its eco-friendly management
Practical Garden-Level Management
For home gardeners and small-scale growers, the most effective strategy is a combination of physical exclusion and timely intervention. Fine-mesh netting draped over brassica beds before the spring flight prevents females from reaching the plants to lay eggs in the first place. The mesh needs to be sealed at soil level; any gap large enough for a butterfly to enter will be found. Because large whites lay eggs in clusters, a quick visual check of the undersides of outer leaves every few days during flying season catches problems early. The bright yellow egg batches are easy to spot and can simply be crushed by hand.
If caterpillars have already established, hand-picking the gregarious groups is practical on a garden scale. Their habit of feeding together in the early instars means you can remove dozens in a single pass. A Bt spray timed for the first-instar stage is effective if hand-picking is impractical, and it breaks down quickly in sunlight, posing minimal risk to pollinators. Neem sprays add an egg-deterrent layer but work best as a preventive application before heavy egg-laying begins.
Crop rotation and removing wild brassicaceous weeds such as charlock and hedge mustard from field margins can reduce the local reservoir of host plants. However, given that migrating females can arrive from hundreds of kilometers away, local habitat management alone will not prevent infestations in high-pressure years.
The New Zealand Eradication
Perhaps the most dramatic chapter in the recent history of P. brassicae played out in New Zealand. In May 2010, the large white was discovered in the Nelson region of the South Island, the first time the species had been detected in the country. New Zealand has 83 native species of Brassicaceae, 81 of which are endemic and found nowhere else on Earth, and many are already threatened by habitat loss. The prospect of a voracious new herbivore added to those pressures prompted an aggressive response.16PubMed Central. Eradicating the large white butterfly from New Zealand eliminates a threat to endemic Brassicaceae
DNA analysis of the Nelson population found three mitochondrial haplotypes, two of which matched sequences from Spain, Romania, Pakistan, and Germany, suggesting a European or western Asian origin but not pinpointing a single source.17New Zealand Plant Protection. Mitochondrial cytochrome c oxidase subunit I sequence variation in New Zealand and overseas specimens of Pieris brassicae (Lepidoptera Pieridae) The population had spread over about 100 square kilometers, mostly through urban residential gardens.
An initial containment effort began immediately, followed by a full eradication campaign launched in November 2012. The campaign combined public engagement (including a short-term bounty for confirmed sightings), systematic garden-by-garden searches, removal of host plants, ground-based insecticide spraying targeted at eggs and larvae, manual searching for pupae, netting of adults, and mass releases of Pteromalus puparum pupal parasitoids reared in the laboratory.16PubMed Central. Eradicating the large white butterfly from New Zealand eliminates a threat to endemic Brassicaceae The last detection of P. brassicae in New Zealand occurred on 16 December 2014, and the species was officially declared eradicated on 22 November 2016, roughly four years after the eradication attempt began and six and a half years after the original detection. It was the first butterfly species ever to be eradicated from a country.16PubMed Central. Eradicating the large white butterfly from New Zealand eliminates a threat to endemic Brassicaceae
The success hinged on several factors that would be nearly impossible to replicate in Europe or mainland Asia. The population was geographically confined and relatively small. New Zealand’s island isolation meant no ongoing immigration from neighboring regions. The campaign had strong public cooperation: residents opened their gardens for searches and reported sightings. And critically, every life stage was targeted with a specific tool, from Bt and insecticides for eggs and larvae to hand-netting for adults and parasitoid releases for the hard-to-find pupae. The case stands as a proof of concept for insect eradication when early detection, public will, and geographic containment align.
Why the Large White Is Harder to Manage Than the Small White
Gardeners sometimes lump all cabbage whites together, but P. brassicae poses distinct challenges. Its egg-laying in clusters means a single female can deposit 50 or more eggs in one spot, creating an instant outbreak zone. The caterpillars’ gregarious behavior amplifies the damage: while a lone small white larva might chew a modest number of holes, a colony of large white caterpillars working the same leaf skeletonizes it rapidly, then moves en masse to the next. The regurgitation defense makes the larvae less palatable to many generalist predators, and as discussed above, even specialist parasitoids adapted to the small white sometimes fail against P. brassicae.9Ecological Research. Response of the wasp (Cotesia glomerata) to larvae of the large white butterfly (Pieris brassicae)
The migratory habit adds another layer of difficulty. Even if you eliminate a local population, a migratory wave can repopulate a field in a matter of days. In parts of northern Europe, the most damaging generation is often the second one, bolstered by immigrants from farther south. Monitoring flight activity and coordinating control timing with regional butterfly-recording schemes, where available, can help growers anticipate these surges rather than react after the caterpillars are already established.