Gunnera (Giant and Chilean Rhubarb, Gunnera tinctoria, G. manicata and all varieties) is a significant threat to cliff, wetland, and riparian ecosystems, spreading quickly by seed and rhizomes, and shading out native plants. It can also block drains, limit access to natural areas, and contribute to erosion.

The RPMP's eradication programme targets known infestations through regular treatment and monitoring. These coordinated efforts have reduced Gunnera at managed sites and continue to prevent its establishment at new locations.

The eradication programme focuses on early intervention to limit spread and protect high-value habitats.

Think you may have spotted Gunnera? Give us a call on freephone 0508 800 800.

Himalayan balsam (Impatiens glandulifera) is a fast-growing plant that produces up to 2,500 seeds per plant. Its seeds spread quickly by water and can stay viable for over 18 months. This allows it to establish along waterways, wetlands, forest edges, gullies, and other moist, sunny areas. The plant competes with native vegetation and can dominate stream banks, leaving them bare and prone to erosion over winter.

Horizons’ eradication programme targets the 20 known sites in the region, with regular monitoring and follow-up control.

New infestations are occasionally found, but the seedbank remains small and manageable, and ongoing work is maintaining progress towards eliminating the species across the region.

Think you've spotted Himalayan Balsam? Give us a call on freephone 0508 800 800.

The rook eradication programme in the region is on track to meet its goal of eradicating breeding rookeries and progressively contain or reduce rooks across the region by 2027.

Rooks are a serious pest for agriculture and horticulture as they can damage crops and reduce pasture productivity, leading to economic losses.

Horizons has reduced the number of active rookeries from 2942 in 2005 to 79 in 2025.

Only Horizons’ operators should undertake rook control. The best method of control is aerial treatment of nesting sites which requires access to treetops. Other methods of control risk disturbance and further dispersal of birds to new areas.

Progress has been driven by coordinated control efforts during breeding season, including aerial treatment of nesting sites, with year-round responses to sightings. Shared knowledge and collaboration with neighbouring councils have strengthened efforts.

Landowners/occupiers must report rookeries to Horizons’ pest animal team on freephone 0508 800 800 or email PCO@horizons.govt.nz. Control of rooks must be carried out by experienced operators – do not take any action to hunt rooks yourself.

Banana passionfruit (Passiflora tripartite (all varieties), P. tarminiana, P. mixta, P. pinnatistipula, P. x rosea) can affect the survival and distribution of indigenous plants and animals, as well as the sustainability of natural ecosystems.

It is a fast-growing vine that can have major impacts on native ecosystems. It forms dense growth that smothers plants and prevents natives from establishing.

Horizons manages banana passionfruit under a progressive containment mapped programme, with officers undertaking control in the active management zone.

The programme focuses on gradually decreasing the spread of the species and protecting high-value ecosystems.

Regular monitoring and control are carried out where budgets allow. Control can be difficult where access is limited, particularly in carbon forestry areas where pines are sensitive to herbicide.

Possums are a widespread pest in our region, affecting native plants and animals, agriculture, forestry, and can spread diseases including bovine tuberculosis, Giardia, Cryptosporidium, and Leptospira.

Horizons runs a large sustained control possum control programme, funded by ratepayers, and takes over new operations as OSPRI withdraws from land, where funding is available.

The programme includes 166 operations, over 210,000 bait stations, and more than 100,000 refills every year. Monitoring consistently shows possum numbers below the target of 10% residual trap catch, demonstrating that the programme is effective.

A recent social return on investment analysis showed that every $1 invested by Horizons delivered $1.63 in social benefit.

While some public conservation land remains untreated, and land-use changes or opt-outs can limit overall effectiveness, the sustained control programme shows how coordinated, long-term efforts can deliver measurable results for our region.

Angus’ farm in Taihape has been part of Horizons' sustained control possum control programme since 2012. By 2022, residual trap catch was 0.9%.

Native plants have flourished: dwarf mistletoe (Korthalsella clavata) is now abundant, young maire trees are fruiting heavily, and tōtara trees are showing new growth that was previously heavily browsed by possums.