Dec. 1, 2015
The New Zealand Environmental Protection Authority (EPA) seeks submissions on an application to introduce a moth and a leaf-feeding beetle as biological control agents. If approved for release, the moth Lathronympha strigana and the leaf-feeding beetle Chrysolina abchasica would be used to help control the weed tutsan (Hypericum androsaemum), which is threatening hill country farming.
The application, from the Tutsan Action Group, is made under the Hazardous Substances and New Organisms (HSNO) Act 1996.
Tutsan is a small perennial, semi-evergreen shrub that grows to 1.5 metres high. It has pale yellow flowers and red fruit and was probably introduced as an ornamental garden plant prior to 1870. By 1924 it was known as a weed, but it is only since the 1950s that it has been seen as a real threat to hill country farming.
Tutsan can be found from Kaitaia to Stewart Island and its effects are worst in the central North Island where it is becoming more abundant. It also affects conservation values, competing successfully with native vegetation in vulnerable places like stream margins and regenerating scrub.
Current control options available for tutsan are limited and expensive. Biological control agents, i.e. the moth and beetle, are self-dispersing and can locate isolated host plants that are otherwise difficult to access. The aim is to decrease the vigour of growing plants through the introduction of the biological control agents’ interaction with the plants, limiting the ability of the weed to persist in existing sites, and/or directly reducing the amount of seed available for dispersal to new sites.
Several potential control agents that could work together have been identified for the control of tutsan. This application proposes to introduce two agents, the moth Lathronympha strigana and the leaf beetle Chrysolina abchasica. The larvae of the moth feed on the leaves and stems of the tutsan plant in spring and inhabit the fruit, consuming the seeds inside. The leaf beetle larvae browse on the leaves, and in large enough numbers cause defoliation.
Tutsan belongs to the family Hypericaceae, which contains four native species. The host range testing, carried out by Landcare Research, is presented in the application and suggests that native plant species will not be at significant risk if these biological control agents were released. There are 14 other exotic Hypericum species present in New Zealand. Some may be susceptible to incidental damage, but damage is unlikely to be economically or ecologically significant. No other adverse environmental, economic, cultural or social effects are considered significant.
The public are invited to make submissions on the application to the EPA. The submissions period opens on 1 December 2015 and closes on 10 February 2016.