Threats

Threats include the arrival of new invasive species into New Zealand, which are a threat to our environment. These invasive species can include plants, animals, insects, birds, fish and diseases. Some recent examples include, scrambling lily (Geitonoplesium cymosum), devils tail (Polygonum perfoliatum), devil’s fig (Solanum torvum), painted apple moth (Teia anartoides), eastern banjo frog (Limnodynastes dumerilii), fire ant (Solenopsis invicta), argentine ant (Linepithema humile), lesser banded hornet (Vespa affinis), southern saltmarsh mosquito (Aedes camptorhynchus), gum leaf skeletoniser (Uraba lugens), marron (Cherax tenuimanus) and gudgeon (Gobio gobio).

Scrambling lily was first found in the Auckland region in October 2000 growing in an area of native bush on the North Shore. Scrambling lily is native to many countries of the Pacific rim, it is a fast growing climber, with wiry stems that wind around and can strangle the trees it climbs. In May 2001 a second site was found on Waiheke Island, at Rocky Bay. Declared an unwanted organism in May 2001, initial sites were removed late May and areas around these sites were surveyed. Two small infestations were found and treated near the initial site. Each year the sites are surveyed by ARC Biosecurity staff and any seedlings or plants found are treated.

Devil’s tail (Tearthumb) was first discovered in March 2000 in Market road Epsom. A serious weed in a number of places overseas it has the potential to be a major agricultural and environmental weed in New Zealand. Devil’s tail is a fast growing annual vine with numerous curved, sharp prickles on the leaves. The plant was declared an unwanted organism on 27 June 2001; the initial site has been cleared with surrounding properties surveyed with no further plants found to date.

Devil’s fig was found growing in a Taupaki nursery in August 2000 during a general surveillance inspection by Biosecurity Officers. This was the second record of this plant found growing in New Zealand. Plants found were destroyed, as devil’s fig is a serious weed in some parts of Melanesia and Australia. Devil’s fig is a shrub growing 1–3 metres high with prickles present on stems and leaves, the plant originates from the West Indies.

A number of freshwater marron crayfish and gudgeon fish were discovered at a West Auckland commercial premises and at a pond at South Head in 2005. At both sites the ponds were drained and the gudgeon and marron were destroyed by Biosecurity Officers. Both the marron and the gudgeon pose a significant threat to native freshwater species such as koura and small native fish and are classified as Unwanted Organisms under the Biosecurity Act. Biosecurity New Zealand, ARC and DoC, worked in collaboration to establish if there were any further populations in the region and to eradicate them.

In 1999 eastern banjo frogs were discovered at Mt Albert and Baker stream in the Waitakere ranges. Banjo frogs pose a serious biosecurity threat to New Zealand’s insects and native frogs, and have been classified as unwanted organisms. All frogs, tadpoles, froglets and eggs found at these sites were destroyed by Biosecurity Officers. Detailed surveys, monitoring and a publicity campaign were carried out throughout the region. Other possible breeding sites were surveyed and monitored with no evidence of banjo frogs found during these surveys.

Contributer:
Greg Hoskins

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