We have found ourselves in the middle of a biosecurity alert. The “Great White Butterfly” appeared in Nelson a couple of years ago and apparently presents a serious threat to horticulture in the region. At the moment there is a team of 20 or so, scouring the neighbourhood looking for signs of the pest. Here’s what the caterpillars look like:
Our property was inspected two months ago. No sightings, but we were told what to look for and asked to remove where possible plants that the butterfly likes: brassicas and nasturtiums in particular. Recently we heard that infestations had been found in neighbouring properties above and below us on the Port Hills.
On the weekend we noticed a fresh patch of nasturtiums at the bottom of a neighbour’s section, in a spot which would be out of their sight. We called the hotline and the next day an inspector arrived. She examined everything carefully before removing any plants (and contacted the neighbour, of course):
Then she found some (the little guys shown in that first picture).
The next step was to remove all of the suspect plant material, without losing any of the larvae. It took quite a while.
Let’s hope the eradication efforts succeed. You can read more about the problem in these links: