Moth and beetle join forces in the fight against tutsan

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.


Potential biocontrol agents against Tutsan are settling into containment

Landcare Research scientists are investigating two small European insects as potential biocontrol agents against the pest plant Tutsan (Hypericum androsaemum).

Tutsan is a significant pest in parts of the Central North Island because it forms extensive patches that take over agricultural, production and conservation land. It is unpalatable to stock, hard to kill, and shade tolerant and is particularly prevalent in areas where the land has been disturbed by the likes of forestry – much like gorse and broom does.

It can be spread by birds and possibly possums as well as soil and water movement and common seed sources include roadsides, farms, wasteland, old gardens, and even roadside mowing. It has been estimated that the cost to land values and cost of production losses due to Tutsan is up to $30 million each year.

Hugh Gourlay from Landcare Research recently travelled to Georgia in Europe to collect specimens of a leaf-feeding beetle (Chrysolina abchasica) and a fruit, leaf and stemfeeding moth (Lathronympha strigana) that are known to attack Tutsan.

Continue reading