Molesworth Station

New Zealand’s biggest farm, the 180,787 hectare Molesworth Station, is part of a vast, mountainous landscape in the northern South Island high country. It is one of the last large farmed areas where possums and other vectors of bovine TB are still being brought under intensive control.

Molesworth is the focus of a nine-year programme of targeted possum control and wildlife surveillance, beginning winter 2017.

Current Operational Progress

Operation Hectares Status Further information
Upper Awatere Molesworth
- Ground control
27,900 Completed for 2019/2020

Molesworth TMA Notice

Bush Gully Aerial 21,500 Proposed for May 2021


Tarndale Aerial 40,000 Proposed for May 2021


Map of Molesworth Control Areas

Molesworth Control Areas 450w


This large high-altitude property was originally excluded from the official pest control programme under previous National Pest Management Strategies that were initially focussed on the reduction of infected herds.

Between 2011 and 2016 the TB programme focussed on keeping infected herd numbers as low as possible while proving TB freedom was possible in large scale possum habitat. During this period, Molesworth Station entered into a 50/50 partnership arrangement with the TBfree New Zealand to undertake local wild animal control on the station. The targeted control work has achieved significant reductions in the number of TB infected animals within the herd.

With the plan to eradicate TB from NZ by 2055, it is essential to implement a substantial TB management programme for the Marlborough/Canterbury high country to achieve this eradication goal. In addition to the programme on Molesworth Station, extensive work is being undertaken within the Clarence Reserve to the north east

OSPRI has worked in partnership with Landcare Research to determine the relative effectiveness of aerial 1080 baiting strategies to reduce both possum abundance and TB levels in wildlife in high country landscape on Molesworth Station.

TB Freedom at Molesworth

As OSPRI manages disease eradication through its TB Management Areas in other parts of New Zealand, a customised two-pronged approach will be used at Molesworth. 

Pest Control Programme

Molesworth Station will be split into large blocks for the purpose of implementing a rolling pest management programme to achieve full coverage over three years. The rolling cycle works in with the station farming practices, makes efficient use of a constrained budget, and ensures that recreactional users have as much access and time as possible to visit the station. Ground-based possum control and aerial distribution of possum baits will be used, with proposed activities communicated and consulted upon as they are designed.

Disease Management Programme

TB tests are designed to measure an animal's immune response. The primary test is a skin test, with follow-up blood tests used in most cases. TB testing for the Molesworth cattle herd will include blood testing the replacement stock. This will be extended to other stock as the pest management programme is implemented.


A farm the size of Molesworth – a landlocked, mountainous area roughly the same size as Stewart Island – presents challenges for people farming and visiting the station. Among them:

  • The country’s highest altitude public-access road makes clear access weather dependent
  • As a working farm, stock management and timing are necessary considerations
  • It’s a popular area for deer, pig and gamebird hunters
  • The rivers and mountains are popular for tramping, mountain biking, fishing and river rafting.

Hunting on Molesworth

Hunting is restricted in Molesworth as it is both a recreation reserve and a working farm, and there is a 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. OSPRI consults annually on its pest control operations.

Reducing deer by-kill during Molesworth possum control

Deer are not the target of our possum control operations but deer deaths are anticipated even with the use of deer repellent bait. The last Molesworth aerial operation, which took place in Acheron East in 2017, resulted in unexpectedly high non-target deer by-kill. A number of factors contributed to the high number of deaths including the use of non-deer repellent bait. Population surveys after the operation show that population recovery has begun and could be expected to be back at its previous level within 6–7 years.


New deer repellent baits suitable for use in high country environments have now become available. Deer repellent bait will be used over the entire operational area in 2020 to improve deer survival rates. Deer repellent is added to both prefeed and toxic baits. We are also seeking to reduce by-kill of deer through operational changes.


TB Management Area factsheets available here. Factsheets on various aspects of TBfree programme activities include:


Byrom A, Nugent G, Yockney I, Poutu N, Whitford J, McKenzie J, Shepherd J, Porphyre T 2007. (R-80629) Cost-effective control of Tb in the Northern South Island High Country (NSIHC): Identifying the habitats and vector species requiring control. LC0708/033. 85p. Read it here.

Porphyre, T., McKenzie, J., Byrom, A. E., Nugent, G., Shepherd, J., & Yockney, I. (2014). Spatial prediction of brushtail possum (Trichosurus vulpecula) distribution using a combination of remotely sensed and field-observed environmental data. Wildlife Research, 40(7), 578-587. Read it here.

Nugent, G.; Whitford, J. Yockney, I.J.; Cross, M.L. 2012. Reduced spillover transmission of Mycobacterium bovis to feral pigs (Sus scrofa) in New Zealand following population control of brushtail possums (Trichosurus vulpecula). Epidemiology and Infection 140: 1036–1047. Read it here.

Nugent, G.; Whitford, J. 2008. Animal Health Board Project No. R-10652 Relative Utility of Tb Hosts as Sentinels for Detecting Tb. Landcare Research Contract Report: LC0708/032. 38 Read it here.