Heather beetle won't let it be: TNP proposal

Ruapehu Bulletin, Volume 13, Issue 614, 28 November 1995, Page 1

Heather beetle won't let it be: TNP proposal

A beetle may be introduced to Tongariro Na tional Park to help fight the spread of heather, a weed that is taking over many parts of the park. The Department of Conservation has put a proposal to the Minister of Agriculture to release a beetle which depends solelyon heather for its survival. The proposal is the result of mere than 10 years of research on the heather problem and methods of controlling it. Heather (Calluna vulgarts, or ling heather) is the most widespread and invasive weed iyfJTongariro National Park World Heritage Area. "It is an ecological problem because it has hugely reduced the biomass of indigenous plants in tussock lands, alpine herb fields, frost flats and high water table sites," said Dr Harry Keys, advisory scientist for the Tongariro/ Taupo Conservancy. Dr Keys said the heather invasion interferes with the natural process of regeneration and succession and was threatening the viability of tussock land ecosystems in the area and hence threatening the largest and most diverse alpine ecosystem and landscape in the North Island. The diversity of native insects had already been reduced, potentially leading to at least local extinction of some species. As well, the distribution of special native plants, some of which are rare, is also threatened in the region. Field studies have shown that the invasion by heather is getting worse, and spreading to areas far beyond the national park. Heather has spread into the Moawhango Ecological Region, the Kaimanawa Range, Tongariro and Erua Forest and to land north, west and east of Lake Taupo. Within the park heather continues to spread in tussock lands, wet lands and above the bushline. At present heather is spreading beyond the central area of infestation at rates of up to seven kilometres per year, mainly in northerly and easterly direction. It is projected

that areas as far south as the Tararua Range, near Wellington and some poorer quality farmland may be vulnerable. DoC says careful and thorough research into the control of heather has been undertaken over the past 14 years and scientists and ecologists believe they have a good understanding of heather ecology and spread, its impact on native insects and plants, how it could be controlled, potential impacts of control and cost benefits. "We can see non-biological solutions to the problem being useful only for small areas of high natural or utility value. Introduction of a beetle (Lochmaea suturalis) which depends solely on heather is the only feasible solution," Turn to Page 2

Heather beetle won't let it be: DoC proposal

FROM PAGE 1 said Dr Keys. The beetle would initially be reared out of quarantine at Lincoln University before being released into natural areas of the central North Island. An impact assessment document has been released for public scrutiny as part of the approval process. Copies of document have-been sent to interest groups, government departments and producer groups including beekeepers and nurserymen. Locally, the department of Conservation is holding a public presentation to discuss the release of the heather beetle at the Whakapapa Visitor Centre on Tuesday, 5 December 1995 at 7.30pm. Submissions to the document are invited up to Friday, 15 December. The safety of the proposed biocontrol has been one of the most important aspects of the research carried out, said Dr Keys. There has been extensive testing to establish which plants the heather beetle will eat and can compete its life cycle on. These tests have confirmed the very narrow host plant range of the beetle. When such testing procedures were carried out in the past no unpredicted damage to non-testing plants were reported.

Dr Keys said that impacts on other plants are expected to be negligible. Laboratory tests showed that the beetle fed on some erica and empertrum species and one native species Pentachondra pumila, although more natural field studies have determined these species are not a risk. "We know from overseas experience that the beetle rarely occurs on cultivated or nursery heathers," Dr Keys said. "The beetle has never been recorded as a problem in plants or gardens". Other potential environmental and social impacts were not thought to be significant. The beetle would not become an environmental problem itself or have negative impacts on any native ecosystems or insects. The beetle is not poisonous and does not sting or bite. The beetle is not the final solution and it is understood that it would not eradicate heather completely. Considerable amounts of the plant would probably remain in the landscape. This means there would be less impact on beekeepers than popularly believed, says DoC, and herbicides would still be needed as a complementary form of control in selected areas of high conservation, ecological, recreation or utility value.