The Great White Butterfly

The great white butterfly (Pieris brassicae) was first found in New Zealand in a Nelson city garden in 2010. It is a significant pest of brassica plants in numerous countries. It is far more destructive to plants than the common small white butterfly; its caterpillars feed in groups, rapidly reducing plants to a skeleton.

As well as being a menace in home gardens, the great white butterfly poses a threat to commercial brassica vegetable crops and endangered native cresses – it could cost the country millions of dollars to protect these from the pest butterfly if it became widespread. Threatened crops include forage brassica crops to feed farm livestock for New Zealand’s dairy and meat industries.

The pest butterfly could also have serious consequences for the survival of many of New Zealand’s 79 native cress species.

The Department of Conservation (DOC) is attempting to eradicate the pest butterfly while it is still within a relatively small area in the Nelson Tasman region to prevent it spreading further in New Zealand. The butterfly has been declared an unwanted organism in New Zealand under the Biosecurity Act 1993.

As part of the eradication programme, DOC field staff are searching home gardens for the great white butterfly caterpillars, eggs and pupae (chrysalises). Any found are removed by hand for scientific purposes and the plants they are found on are sprayed with an organic insecticide to ensure any eggs or caterpillars that may have been left are destroyed. Residents in most cases are consulted before any spray is used.

How You Can Help

  • Check your brassica plants such as cabbage, broccoli, cauliflower, rocket, mustard regularly for great white butterfly eggs and caterpillars and report any found to the Ministry for Primary Industries (MPI) Exotic Pest and Disease hotline 0800 80 99 66.
    • Nasturtium (Tropaeolum majus) is also favoured by the great white butterfly. We encourage Nelson Tasman property owners to remove nasturtium in their gardens to assist in eradicating the pest butterfly and also to avoid it attracting great white butterfly infestations.
    • Consider planting cover crops that don’t attract the great white butterfly to your garden. Mustard, a brassica and great white butterfly favoured plant, is often planted in autumn as a cover crop. We suggest planting cereal cover crops such as rye, oats and barley instead.
    • We also ask Nelson Tasman residents to catch and kill great white butterflies to prevent them from laying more eggs. Butterfly nets or tennis and badminton racquets can be used to catch the butterflies which should then be squashed.
    • If you are taking trailers, boats, caravans and campervans out of the Nelson Tasman region please check there are no great white butterfly pupae on board before leaving home. Any found should be reported to the MPI hotline 0800 80 99 66.
    • We also ask Nelson Tasman residents to refrain from moving vegetable garden waste, home grown brassica vegetables such as broccoli, cauliflower and cabbage and brassica seedlings out of Nelson or check it very carefully for great white butterfly eggs and caterpillars before doing so.

Identifying Great White Butterfly

The great white butterfly looks different to the small white butterfly though larger and with different black markings, however, the caterpillars, eggs and larvae are different.

The Great White Butterfly caterpillars and eggs are mostly found in groups while the small white butterfly caterpillars and eggs are mostly found singly.

GWB eggs web The Great White Butterfly's tiny, bright yellow eggs are usually in clusters of 30 to 100 and are mainly found on the underside of the leaves of host plants.
great white butterfly caterpillars on honesty photo Richard Toft web2 Very young caterpillars are tiny and yellowish, with a shiny black head. As the caterpillars grow, they become speckled black and greyish-green with three yellow lines along their bodies. Larger caterpillars have lots of noticeable pale hairs. Fully grown caterpillars are 50mm.

 Download the brochure below to help you to identify the Great White Butterfly:

Further Information

Read about the Great White Butterfly on the DoC website

Contact the great white butterfly eradication team, ph (03) 546 3147

To Report a Great White Butterfly Find

Call the Ministry for Primary Industries (MPI) Exotic Pest and Disease hotline 0800 80 99 66.