By 3 News online staff
The Department of Conservation has put a bounty on the heads of an ecological pest it wants dead.
DOC has issued a $10 reward for each great white butterfly caught in the Nelson region during the school holidays.
And the offer isn't just open to children; adults are also encouraged to catch and kill the butterflies and bring them in to claim their bounty.
Conservation Minister Nick Smith says the butterflies are a threat to endangered native cresses, as well as plants like cabbage and broccoli.
"To date they have only been found in Nelson/Tasman region, but we must do everything we can to ensure they don't become a permanent widespread pest."
They are mostly found in and around the Port Hills area of Nelson, but have also been found in Stoke and the Glen.
Female great white butterflies can lay as many as 750 eggs, so every butterfly killed potentially stops up to 750 more butterflies hatching, Dr Smith says.
DOC says the butterflies should be put in a jar or sealed plastic bag and stored in the freezer so they don't go mouldy. They can be dropped off to the department's Nelson office on weekdays between September 30 and October 11.
The bounty will only be distributed between these dates and for adult butterflies.
Great white butterflies can easily be confused with small white butterflies, but DOC says those are still considered garden pests.
The department would also like people to bring in small white butterflies to make sure they're not great white ones.
Though there won't be a reward for small white butterflies, those who bring them in will go into the draw for spot prizes.