The Environmental Protection Authority has enlisted the help of a moth and a beetle to get rid of a highly visible and widespread weed in the central North Island.

Considered a serious agricultural and environment pest in the central North Island Tutsan (Hypericum androsaemum) is a yellow-flowering shrub introduced into New Zealand as a garden plant in the 1800s.

The moth larvae which will help reduce the tutsan shrub. Photos: Supplied.

By 1924, tutsan had grown out of control 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.

The leaf eating beetle.

As a result, tutsan cannot be bought, sold, propagated, distributed or included in commercial displays.

Now the Authority has approved the use of two biocontrol agents: a moth and a leaf-feeding beetle to help in the fight to combat the weed.

A close up of the tutsan shrub.

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 damage the tutsan can do if left to its own device.

The leaf beetle larvae (Chrysolina abchasica), in large enough numbers, are capable of stripping the plant of its leaves says Environmental Protection Authority acting general manager of hazardous substances and new organisms Ray McMillan.

'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.

'Tutsan is a significant problem throughout New Zealand and is a threat to native plants and hill country farming.”

Ray says 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.”