The Environmental Protection Authority (EPA) has approved a moth and beetle to help stamp out tutsan, or Hypericum androsaemum). which is 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.
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.
Ray McMillan, the EPA’s Acting General Manager of Hazardous Substances and New Organisms, says 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.
The application to use these agents was made by the farmer-led Tutsan Action Group.