Upping the ante on ants

Invasive and potentially destructive ants have been discovered in more than 12 sites in Marlborough.

Ant survey co-ordinator Mike Bell said two pest species, Argentine and Darwin's ants, were found in a survey last summer.

Both species, which are easily spread and highly invasive, could potentially threaten the viticulture and horticultural industries if populations got out of hand.

If they landed on any of the Department of Conservation protected islands in the Marlborough Sounds, home to threatened native species, the effects could be disastrous.

Before the survey they were known to live in Marlborough, but there was no information on distribution or abundance.

The survey found Darwin's ants, first seen in Blenheim in 2001, were located in one site each in Seddon and Renwick and six sites in Havelock and well established in Blenheim and Picton.

The more destructive Argentine ants were found in one large site in Blenheim and a small Picton site.

They are one of the most invasive and problematic species and worldwide the species is listed in the top 100 invasive pests list.

Both species are known to invade homes and fridges, and some people are sensitive to their bites, although they are not poisonous.

Commissioned by the Marlborough District Council, the study was carried out by forest management company Te Ngahere Ltd.

During the survey about 1200 baited pottles were set out across Ward, Seddon, Blenheim, Picton, Renwick, Havelock, Rai Valley, Okiwi Bay, French Pass, and D'Urville Island.

Another 40 samples were collected from private homes.

Mr Bell said a three-phase survey was under way to find out the exact extent of the ants' infestation.

Results from that survey will be presented to the council's environment committee late next month.

- The Marlborough Express