Bio lure smells end for redbacks

Weta a winemaker’s bugbear Chemicals based on pheromone produced by female showing promise as bait to entice males into traps

It’s a conservation conundrum: what to do with a potentially threatened native species that’s been making a pest of itself? The endemic bug, formerly known as the Cape Campbell ground weta, has proven a nuisance for winemakers in Marlborough’s Awatere Valley because of its fond taste for grape vine buds. On warm dark nights, at the time of year when the buds are bursting, the weta crawl out of their burrows in the vineyards and feed on the swelling buds. Lincoln University researcher Jerry Nboyine, who works in

Acunning new weapon could spell the end for one of our most feared and unwanted pests. The venomous Australian redback spider, characterised by the red strip across its swollen black abdomen, is found in several areas in Central Otago and New Plymouth, and its spread to other regions has remained a constant biosecurity worry.

Its incestuous nature means it can breed more freely than other species, and its thick web has helped it get past Customs checks.

But it’s more notorious for the toxic venom that a single bite can deliver to a person unlucky enough to encounter one.

“One in three bites comes with a severe reaction, but even mild reactions aren’t that mild,” Otago University researcher Stacey Bryan said. the collaborative BioProtection Research Centre, said one year vineyard owners lost a third of their annual yield in a few weeks. “The buds are also relied upon to produce the following year’s yield — so without having any canes to lay down for the next year, it causes a lot of panic.” If they were dealing with a recognised pest, winemakers might combat this threat with pesticide. Mr Nboyine said it wasn’t known whether these weta were threatened as their conservation status was unclear. Mr Nboyine has been

“They’ve been described to me as feeling like you’re going to die for a period.”

They also pose a worrying and growing threat to endemic species they prey on.

Ms Bryan has observed them predating 10 native species, including the nationally endangered Cromwell chafer beetle and the McCann’s skink — the first time redbacks have been recorded attacking skinks since the spiders were discovered here in 1981.

She was concerned what this could mean for the endangered Otago and grand skinks, found throughout Otago, if redbacks became rampant.

Working with Canterbury Museum arachnologist Dr Cor Vink and other colleag- working with vineyard owners to find ways of minimising the impact of the insects, which has included tying plastic sleeves around the vine bases to prevent them climbing up to the buds. But that method was expensive, as the plastic tore and soon needed replacing. “We want to make sure that we prevent vine damage without killing the insects, which is an unusual challenge,” he said. “Early data are showing that simply sowing tasty broad beans between the vine rows can tempt the weta away from the vines. ues, Ms Bryan has developed a new biological control that could potentially stop their spread — and perhaps even wipe them out in New Zealand altogether.

It lies in two chemicals identified by Dr Vink, which were suspected to be the active ingredients in the pheromone that female redbacks laced their webs with to attract males.

“So my job was essentially to first see if males were attracted to these chemicals, and to see if we could make a biological control out of them,” she said.

Her experiments found that while the chemicals weren’t powerful enough to eclipse the attraction of the females’ natural pheromones, they could still equal it — meaning at least half the males could be lured to their deaths in traps.

“So it still needs a bit of tweaking for us to get a superstimulus, but we are three quarters of the way there.”