The Otago Regional Council has sounded a note of caution over the effectiveness of new aerial rabbit poisoning methods being trialled in Central Otago.
The council and Landcare Research are investigating ways to reduce both the cost of rabbit control and the amount of 1080 poison used.
Staff and contractors last week carried out "pre-feeding" on Bendigo station in readiness for a "toxic drop" in about a fortnight.
Instead of blanketing the land with bait, the experiment involves dropping bait in "swathes" up to 125m apart. This reduces the flying time required and the amount of 1080 used.
However, council senior field adviser Peter Preston, who has been working on rabbit control for about 30 years, cautioned recently it was too soon to be certain the new method would be as effective as the old.
"This is not proven yet. It is only theoretical."
Last month, the Landcare scientist involved in the work, Dr Dave Latham, told the Otago Daily Times five experiments were done last year - reducing by as much as two-thirds the amount of toxic bait being used.
Dr Latham said then: "We do not see that there is anything that we have done that does not work as well as current practice."
However, Mr Preston said while last year's trials looked "reasonably promising", there were a few anomalies, a few gaps in the information, a few things that weren't quite right.
"So, obviously, it needs to be ongoing for a number of years to prove the theory."
Mr Preston said a kill rate of 95% was needed to have a long-term effect on the rabbit population.
"If we have, for instance, a situation where we halve the cost but we only get a 90% kill, that would probably not be a good thing because we would need to be carrying out control at a more regular interval than we perhaps would have been if we had done a conventional treatment."
The trial also involves Cluden Station.
