Molesworth Station is New Zealand’s largest working farm, spanning 180,787 hectares in the mountainous landscape of the northern South Island high country.

With over 30 years of continual infection, the Molesworth cattle herd is the longest-standing TB infected herd.

Current operational progress

OperationApprox. hectaresStatus
Acheron East62,500Proposed from October 2022
Tarndale and Bush Gully68,000Operation complete 2021
Saxton Strip Sow6200Operation complete 2021
Severn Low Sow5400Operation complete 2021
Yarra / Five Mile7700Operation complete 2021

Map of Molesworth control areas


Before 2017, the TB programme focussed on keeping infected herd numbers as low as possible while trying to prove TB freedom was possible in a large-scale possum habitat.

During this period, Molesworth Station entered into a 50/50 partnership arrangement with TBfree New Zealand to undertake local wild animal control on the station. This work achieved significant reductions in the number of TB infected animals within the herd.

The plan is to eradicate TB from New Zealand by 2055, so we need to implement a substantial TB management programme for the Marlborough/Canterbury high country to achieve this.

TB freedom at Molesworth

Our national milestone of TB freedom in livestock by 2026 means we are taking a multi-pronged approach to eradicating TB in the cattle herd and possum population on Molesworth Station. We will do this through:

  • herd TB testing of all age groups annually
  • TB surveillance at slaughter
  • farm and stock management practices to monitor TB risk
  • pest management — control and surveillance
  • research and innovation.

Our objectives are:

  • Molesworth Station cattle herd reaches TB free status by June 2023
  • possums at Molesworth Station are TB free by June 2027.

Pest Control Programme

Molesworth Station is divided into blocks for possum control work. We achieve full coverage every three years.

Due to the mountainous nature of the environment, aerial methods of pest control ensure full coverage, and best use of time and resource.

Successful trials of aerial low sow baiting

In June 2021, we trialled two new approaches to aerial baiting.

  • Severn Trial Area — we treated 4,868 hectares with 50% less bait (1 kilogram per hectare). We used standard broadcast methods, so achieved complete coverage.
  • Saxton Trial Area — we treated 4,356 hectares with 60% less bait (0.8 kilograms per hectare). In this case we applied bait at 2 kilograms per hectare in 30-metre-wide strips, with non-treated gaps of 100 metres between strips.

Both trials achieved 100% poisoning of possums with lower sowing rates shown to be effective in dryland habitat where bait easily reaches the ground.

Due to the success of the trials in this high country environment it will be a method that we use for future aerials here and in the Northern South Island high country.

Hunting on Molesworth

Hunting is restricted on Molesworth as it is both a recreation reserve and a working farm. We need to balance the requirements of both.

Red deer, chamois, goats and pigs are found on the station, and hunting is restricted at times, such as during the annual goose hunt.

We consult annually on our pest control operations.

Reducing deer deaths during Molesworth possum control

Deer standing in grassy areaAccidental deer deaths occur during our possum control operations, even with the use of deer repellent bait.

The 2017 aerial operation in Acheron East resulted in unexpectedly high deer by-kill. A number of factors contributed to the high number of deaths, including use of bait that didn’t repel deer.

New deer repellent baits suitable for use in high-country environments are now available. In the recent 2021 Molesworth aerial operation, we focused on improving deer survival rates by:

  • adding deer repellent to prefeed and toxic baits
  • trialling different aerial timing and sowing methods.

Research papers

High effectiveness of deer-repellent Prodeer 1080 possum bait in the northern South Island high country — (R-1005) Morriss, G, Yockney, I, Nugent, G. 2021.