Wasp wipeout humming along Cable Bay walkway
Wasp control along a popular trail north of Nelson is in full swing, ensuring walkers can still get a buzz out of the outdoors.
As autumn takes hold, the sound of cicadas has dissipated, leaving the hum of bees and wasps to compete with birdsong as the dominant voice in the bush.
The german wasp (Vespula germanica) and common wasp (Vespula vulgaris) have been described as New Zealand’s most abundant and devastating invertebrate pests.
New Zealand has some of the highest densities of german and common wasps in the world, thanks to mild winters, plenty of available food, and a lack of natural predators.
Wasps are a major problem in beech forests, where they consume massive amounts of honeydew.
This week, work continued on controlling the wasp population in the Cable Bay walkway, which is located on hilly terrain and farmland between Glenduan and Cable Bay.
The work is being carried out by staff from Ku¯ma¯nu Environmental, a division of Nelson-based asset management company Nelmac, which is involved with projects such as weed and pest control as well as track cutting.
The company manages wasp baiting projects around the Cable Bay walkway and Hackett areas of the region, in conjunction with Department of Conservation.
The meat-based poison Vespex, containing 0.1 per cent fipronil, is placed in wasp stations at 50-metre intervals along the 8-kilometre Cable Bay track, which is lush with ma¯nuka and beech vegetation.
Ku¯ma¯nu senior ranger John Whibley said the poison was similar to that used in flea treatment of animals. Only wasps are attracted to the Vespex. ‘‘It’s the rate of mix that’s important. If it’s too strong, the wasp will die before it gets back to the nest; too weak and the poison will have too little effect,’’ he said.
By autumn, the wasps have moved from a carbohydrate-based diet to a protein-based one.
Whibley said the wasps had been more active and aggressive since the beginning of April. ‘‘At this time of year, when it feels quite cold in the morning, that’s when they’re looking to get the protein and that’s when this bait comes into its own.’’
Initially, an audit takes place to ascertain the population and ensure the wasps have switched from a carbohydrate to a protein diet and are therefore attracted to the bait.
‘‘They’ve really come on to the protein in this area in the last couple of weeks. Before that, they failed the audits so there wasn’t enough wasps around – but now there is.’’
If that’s successful, the bait is then put out and left for a few days. As it is not toxic enough to kill the wasps straight away, they take it back to the nest. ‘‘Word gets out and more wasps come back – you should get a whole nest collapse within a day or so.
‘‘They’ll come from a fair way to find it, but ideally you want to have a network of stations in place. You don’t actually have to find the nest because they’ll find the bait.’’
Whatever bait has not been taken is removed from the site between three and eight days later, while stations are cleaned and reused the following year.
Whibley said the bait work should have a positive impact on visitors’ enjoyment of the high-foot-traffic area as well as on bird and bee life.
Wasp Wipeout is a partnership between Conservation Volunteers New Zealand, DOC, Stuff Ltd, the Tasman Environment Trust and councils, with the aims of reducing Vespula wasp populations and spreading awareness of the threats caused by these species.