Japanese butterfly takes flight
Honshu white admiral pupa
New Zealand’s newest butterfly, the Honshu white admiral (Limenitis glorifica), has established well near the Coromandel Peninsula and is starting to spread its wings in other regions where Japanese honeysuckle (Lonicera japonica) is a target weed.
The butterfly was first released near Paeroa, in the Waikato, in November 2015 and the population has continued to thrive there. After initial difficulties trying to rear the butterflies in captivity, suddenly there has been great success. “We tried almost everything to get the butterflies to mate, including handpairing them and releasing them in a purpose-built butterfly house, but never got fertile eggs,” said Quentin Paynter, who has been leading the project. “Because we couldn’t get them to mate in containment, we had to import field-collected adults from Japan that had already mated and release their progeny and hope for the best. Luckily this worked and the butterfly became established,” said Quentin.
“We returned to the release site in the spring of 2016 to harvest butterflies for redistribution,” he said. “The plan was to collect mated adult females from the field and use their offspring for redistribution, but Chris Winks decided to keep a few larvae, rear them through to adults and release them in one of our shade houses at the Tamaki Campus in January 2017,” Quentin said. Amazingly, the conditions in the shade house were conducive to mating, resulting in an astonishing number of caterpillars that chewed through large quantities of Japanese honeysuckle plant material.
“Due to logistics and staffing resources, we decided to shift the butterfly rearing operation from Auckland to Lincoln. But no-one really expected that we would have a glasshouse full of butterflies quite so quickly,” said Hugh Gourlay, who has been managing the rearing. “It was an amazing sight, and quite a few of the staff from around the campus came over at lunchtime for a stroll through the glasshouses and an ‘out of office’ experience,” Hugh said.
As a result of this success, 12 more releases in other regions of New Zealand have been made this summer. Hugh and colleagues sent out approximately 60,000 mid-sized caterpillars on cut plant material for regional councils to release. “All going well, we should have populations establishing in Nelson/ Marlborough, Wellington, the Bay of Plenty, Taranaki and other parts of the Waikato,” said Hugh. More butterflies will be reared for release next summer.
Japanese honeysuckle remains one of the most widespread weeds in New Zealand and grows especially fast in the warmer conditions found further north. “The caterpillars hibernate amongst the plants during the winter months and can withstand cold temperatures in their native range in Japan, so we don’t think they will be restricted to the North Island,” said Quentin. “It is really a matter of placing them where they are needed most at this stage,” he added.
The other agent being released to control Japanese honeysuckle is the longhorn beetle (Oberea shirahatai), which attacks the stems of the plant. “Rearing this agent has also had its challenges,” said Hugh. This beetle has a long life-cycle and seems to take 2 years as a rule to complete development. Mass-rearing of this agent is therefore very time-consuming and expensive, so the plan is to rear enough beetles to establish them at two field sites, from which they can be harvested and redistributed to other sites in the future.
As a step towards this goal, the first field release of the stem beetle was made at a site in the Waikato this autumn. Holes were drilled into Japanese honeysuckle stems and the larvae inserted inside and then plugged with vaseline. More beetles will be released over time, including adults, as numbers permit. As well as rearing some beetles for the field releases on whole plants at Lincoln and Auckland, which is a very slow process, we are attempting to rear larvae on a highly nutritious artificial diet, to try to speed up development. “At present, this approach is looking quite promising and we have around 300 beetle larvae in tubes of diet in a controlled temperature room at Lincoln, which is set up to simulate winter conditions,” Hugh explained. “We are hoping they will pupate and emerge as adults ready for a field release next summer.”
This project is funded by the National Biocontrol Collective. Read more about the white admiral and watch a video at: www.landcareresearch.co.nz/about/news/snippets/hittingback-at-japanese-honeysuckle
CONTACT
Quentin Paynter – paynterq@landcareresearch.co.nz
Hugh Gourlay – gourlayh@landcareresearch.co.nz