The Department of Conservation is urging the public to kill butterflies.
Not all butterflies, but specifically the great white butterfly that is condemned as a pest and it wants eradicated from the Nelson-Tasman region.
DOC's call to kill comes in anticipation of a spike in great white butterfly numbers as they emerge from pupae in the autumn.
" ‘Kill the butterflies please', is what we're saying now," says DOC Motueka area manager Martin Rodd. "It sounds harsh but it's crucial to stopping their spread. We need to destroy the butterflies before they lay their eggs."
DOC says butterfly nets or sports racquets can be used to catch the butterflies, which should then be squashed.
It says the great white butterfly poses a major threat to commercial and home brassica crops and to native cresses. The adult great white butterfly looks similar to the small white butterfly, though about twice the size. Its caterpillars and eggs are mostly in clusters whereas the small butterfly caterpillar is mostly found singly.
Mr Rodd said people should not be concerned about killing the smaller but similar looking white butterfly by mistake, as it was also a garden pest.
It seems residents are happy to join the killing campaign.
Dozens of people had phoned over summer, many with positive identifications of caterpillars and eggs, which had since been destroyed, he said.
"We still want people to report findings of eggs and caterpillars to the Ministry for Primary Industries hotline - 0800 80 99 66 - but now we really need people to catch and kill the butterflies if we are going to have a good chance of eradicating it."
The butterfly was first found in Nelson city, and a single dead caterpillar was found in Upper Moutere two weeks ago, 20 kilometres beyond the known range of the great white butterfly.
"This find reinforces why it's so important for residents in Tasman, as well as Nelson, to keep a look out for eggs, caterpillars and butterflies," Mr Rodd said.
The tiny, yellow eggs and caterpillars are found in clusters on host plants particularly nasturtium, honesty and brassica vegetables such as broccoli and cabbage. The caterpillars are very small when young and in later stages they are speckled black and greyish-green with three yellow lines along their bodies.
Work to remove uncontrolled nasturtium plants, a breeding favourite with the butterfly, has also been done.
Nelson residents should report patches of wild, uncared-for nasturtium to DOC's Nelson office, 03 546 9335, or email email@example.com
Should Nelson schools offer compulsory classes on sexual consent for teenagers?Related story: (See story)