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 catch and kill great white butterflies to prevent them from laying more eggs. Then contain them -a jar is ideal- and ring the MPI Hotline 0800 80 99 66
- 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
Visit www.doc.govt.nz and search for great white butterfly.
Contact the great white butterfly eradication team, phone (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.