Biological battle against wild ginger

Biological and cyber warfare are two of the latest tools a multi-agency group is keen to employ to tackle a serious weed pest that has invaded thousands of hectares of Northland.

Wild ginger – originally native to Nepal – loves Northland’s warm and wet climate and its high rate of spread makes it an ‘ecosystem transformer’ that has already spread through at least 5000 hectares of the region.

Don McKenzie, Biosecurity Manager for the Northland Regional Council, says it’s a serious problem due to the way it takes over the forest floor and prevents native species from regenerating.

“As the canopy begins to die, wild ginger is the only plant that is left.”

That process is already well under way along parts of Northland’s extensive coastline and wild ginger – a hybrid of Kahili ginger and white ginger introduced in the 1860s as a garden plant – now also threatens some of the region’s most important native kauri forests.

The Stop Wild Ginger Stakeholder Group, whose members include the region’s local authorities, Department of Conservation, Landcare Research, forestry companies and supporting iwi, recently launched a multi-pronged campaign to provide a website and educate the public about the effects of wild ginger.

Small patches of wild ginger can be controlled through digging out by hand or by herbicides, but this is only suitable for areas under one hectare.

Herbicides also often can’t be used as dense bush (where most of the infestations occur) or forestry areas as it affects soil and plants around the treatment site.

Mr McKenzie says New Zealand needs to invest in smarter technologies, with the most effective and sustainable tool for the future likely to be a biological control agent.

“By using a natural predator of wild ginger we will hopefully be able to reduce this plant’s population down to manageable level.”

Officials think there is much more than the 5000 hectares of wild ginger they already know about in Northland and are asking for the public’s help to map all the sites.

n www.stopwildginger.co.nz

INVASION: Biosecurity Manager Don McKenzie is dwarfed by invasive wild ginger in the Helena Bay area near Whangarei.