OSPRI’s TBfree programme is continuing to innovate and improve its operational effectiveness with the successful trialling of aerial low sow baiting and deer repellent bait at Molesworth National Park.

This winter at Molesworth and adjoining private land, the animal disease management agency completed two 1080 aerial operations over 70,000 hectares and the outcomes were excellent for possum control and deer survival in the high-country environment.

Manaaki Whenua - Landcare Research carried out trials which involved the radio-collaring of possums and feral deer for tracking purposes to evaluate bait efficacy.

A new deer repellent was spread across the entire treatment areas. This performed well and was effective in minimising feral deer mortality following the aerial 1080 operations.

From the data collected and analysed:

-100 percent of radio collared possums were eradicated using three different techniques: standard broadcast, low sow broadcast and low strip broadcast

-95 percent of radio collared deer survived the standard broadcast trial

-Researchers also observed 358 non-collared deer within the treatment area, 351 were alive, 7 dead.

"The trials undertaken with Landcare Research at Molesworth are insightful and the results are especially positive. The possum control work was timed to coincide with the start of winter when food is scarce and to enable quicker detoxification of the repellent baits," says OSPRI Research Manager Dr Richard Curtis.

Currently, 1080 aerial control is the most effective tool for achieving nationwide TB eradication in cattle and deer herds by 2026. It has biodiversity benefits by reducing possum, rat, and stoat numbers, and is proven to be particularly effective in aerial baiting programmes for controlling possums - the main vectors (transmitters of TB in cattle and deer) over larger areas of forest or rough terrain like Molesworth.

OSPRI engaged beforehand with deer hunters and recreational groups, Molesworth Station, New Zealand Game Council, Department of Conservation[DoC] and landowners, to minimise disruption to farming and recreation from TBfree operations.

Dr Curtis says, "We’re aware that wild deer and hunting are valued by many people and we’re confident that the results of this deer repellent trial at Molesworth will demonstrate that we can balance the necessary possum control and reduce impacts on the immediate environment.

"You can never rule out feral deer mortality following an aerial operation, but with greater numbers of deer surviving, this will ensure a rapid population recovery throughout Molesworth."

Aerial bait sowing innovation

Aerial bait sowing trials over 9,000 hectares at Molesworth & adjoining private land has potential to reshape how OSPRI undertakes TBfree operations in the future.

In an alternative approach to improve efficiency of 1080 aerial control, the volume and density of aerial sow baits was modified.

A ‘strip sowing’ technique in the Saxton block, and a ‘low sow’ broadcast approach in the Severn block were trialled, and this has provided a 65 percent and 50 percent reduction in toxins respectively.

These techniques are expected to be more cost effective than standard 2kg per/hectares per broadcast and still achieve the necessary possum control target rates.

Both trials achieved 100 percent poisoning of possums with lower sowing rates shown to be effective in dryland habitat where the environment supports good access to bait.

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