Public asked to report pest butterfly

9 March 2012

The Ministry of Agriculture and Forestry (MAF) is calling on Nelson and Marlborough residents to help them locate any further infestations of an invasive butterfly discovered in central Nelson in May 2010.

The great white cabbage butterfly (Pieris brassicae) is regarded overseas as a serious pest of brassica crops. Brassica crops include; cabbage, broccoli, cauliflower, forage kale, swedes and turnips.

It also has the potential to affect New Zealand’s native brassica plants.

The butterfly was first discovered in New Zealand on a nasturtium plant in a private Nelson property in 2010. Since then approximately 50 other infested sites have been found, all within five kilometres of the original site.

MAF has been running a surveillance and treatment programme for the butterfly. The original infestation and subsequent infestation sites have been inspected and treated where necessary.

“The number of individuals at each site was small and would have been the result of a single batch of eggs laid by a female butterfly,” says MAF plant team adviser Bruce Philip.

“Despite the limited spread it is likely that a small breeding population of the great white cabbage butterfly exists in central Nelson. The butterflies are active at the moment and we urge people to call us if they think they have seen its eggs or distinctive caterpillars on brassicas or nasturtium plants.

“Pupae may also be found close to host plants on structures such as fences, poles and buildings. The adult winged butterflies are harder to distinguish as they look similar to the small white cabbage butterfly, which is very common in New Zealand.”

“Information from the public has helped MAF to prevent the spread of the white cabbage butterfly in Nelson. Further information will help us to locate and treat remaining populations and determine whether it is declining or spreading.

“This information will help MAF decide management options for this pest in the future”, says Bruce Philip.

While there is no evidence that the butterfly has spread, MAF is also asking Marlborough residents to report any sightings.

The great white cabbage butterfly hibernates over winter as dormant pupae.

To report suspected sightings contact MAF on 0800 80 99 66.

Photos of the butterfly, caterpillar and eggs are available on request.

ENDS

Media contact: Judith Hamblyn, Senior Communications Adviser, Ministry of Agriculture and Forestry, Ph 04 894 0161