Tutsan Action Group Update
Progress in the battle against the invasive weed tutsan
The Tutsan Action Group was formed in 2007 in the central North Island as a committee of farmers, local council and DOC, to make applications for the search, evaluation, breeding and release of a biocontrol agent. Farmers suffer loss of income estimated to be worth millions of dollars a year.
In total the group raised $1.35 million and the search turned up two control agents in Eastern Europe, which were imported in 2014 and evaluated. The money was raised from contributors including the Ministry for Primary Industries’ Sustainable Farming Fund, Horizons and other regional councils, Landcare Research, Ruapehu District Council, Department of Conservation, Treescape/Kiwirail, territorial authorities, Maori-owned enterprises, forestry, community groups and more than 150 farmers.
Biological control of the invasive weed tutsan is showing considerable promise. Two specialist insect species were imported from Georgia in Eastern Europe by Landcare Research. They are a leaf-tying moth (Lathronympha strigana), which attacks the stems, shoot tips and seed pods of the plant, and a small leaf beetle (Chrysolina abchasica), which attacks the foliage. Both have been in containment at Lincoln since 2014, and appear to be highly damaging to tutsan plants, but not related native plant species. The Environmental Protection Authority approved the release of the moth and the beetle in 2016. Thirty releases took place between January and March in the central North Island, around Taumarunui. There will be more releases next summer, plus surveys to see if the control agents have taken hold and spread.
Tutsan (Hypericum androsaemum) came from southern and western Europe, introduced as a garden ornamental in the 1800’s. It is part of the St John’s wort family. It is a small (under 1.5m) evergreen shrub with fragrant leaves that turn red in autumn. It has yellow flowers and produces round red berries that ripen to black and contain cylindrical or curved seeds. It produces many, long-lived, well-dispersed seeds, tolerates semi-shade, hot or cold temperatures, high to moderate rainfall, any damage and any grazing, but that is rare because livestock do not like it. It spreads through birds, machinery, human activity and possibly possums, and soil and water movement. It invades regenerating sites and forms dense stands, preventing establishment of native seedlings. It colonises disturbed forest and shrubland, low-growing habitats, tussockland, bare land, and rocklands. By 1924 it had grown out of control and has been a growing threat to hill country farming since the 1950s.
Tutsan exists all over NZ but is a significant problem in parts of the central North Island, where it forms extensive patches that threaten agricultural, forestry and conservation land.
Unpalatable to stock, hard to kill and shade-tolerant, tutsan is particularly prevalent in areas where the land has been disturbed by the likes of forestry. It is easily spread by birds, mowers, machinery, and soil and water movement. Common seed sources include roadsides, conservation and wasteland, old gardens and forestry.
Recent research into tutsan populations in NZ has shown that the plant here has two distinct genetic types – one that grows in the North Island and another in the South Island. The North Island plants are not being controlled by the North Island rust anymore, whereas it appears that the other rust type is currently keeping the South Island plant populations under control.