New Zealand EPA approves moth and beetle against tutsan

The New Zealand Environmental Protection Authority (EPA) has approved a moth and beetle to help stamp out tutsan, a highly visible and widespread weed in the central North Island.

Tutsan (Hypericum androsaemum) is considered a serious agricultural and environmental pest in the central North Island. The yellow-flowering shrub was introduced into New Zealand as a garden plant in the 1800s, but had grown out of control by 1924 and has been a growing threat to hill country farming since the 1950s.

It thrives in the central North Island, particularly around stream margins and regenerating scrub. In some areas, such as the Waikato, landowners work with their regional councils to control the weed. Although it’s not toxic, livestock will not eat it and removing it is time consuming: even minor infestations require intensive effort and herbicides are usually used to control or reduce larger infestations. As a result, tutsan cannot be bought, sold, propagated, distributed or included in commercial displays.

Now the EPA has approved the use of two biocontrol agents: a moth and a leaf-feeding beetle to help in the fight to combat the weed. The larvae of the moth (Lathronympha strigana) feed on the leaves and stems of the plant in spring and burrow into the fruit, consuming its seeds. The leaf beetle larvae (Chrysolina abchasica), in large enough numbers, are capable of stripping the plant of its leaves.

“Using biological control agents, or nature’s enemies, is a cost-effective way of targeting and reducing the impact of pest plants such as tutsan without resorting to chemicals,” says Ray McMillan, EPA’s Acting General Manager of Hazardous Substances and New Organisms.

“Tutsan is a significant problem throughout New Zealand and is a threat to native plants and hill country farming. Landowners and regional councils have limited resources to control pest plants and using natural fixes, like the moth and beetle, can be an effective way of managing an invasive pest. They are self-dispersing and can seek out isolated plants that are otherwise difficult for landowners to find or access,” said Mr McMillan.

“Using biological control agents as part of their weed management strategy will provide a cheaper alternative for landowners and councils. And releasing two biological control agents with complementary feeding habits increases their effectiveness. If they both establish successfully and disperse widely they’ll increase the chance of success of the biocontrol programme,” said Mr McMillan.