An investigation in an aerial drop of 1080 that killed eight cattle in the King Country in September 2018 has found that the Department of Conservation breached one of its operating procedures.
The DOC pest control operation was conducted over the 1400ha Mapara Wildlife Reserve, 35km southeast of Te Kuiti.
The livestock got into the area via an insecure fence - something the farm owners dispute - and ate the poison.
The inquiry by the Environmental Protection Authority found that DOC did not advise the cattle's owners, Mark and Paula Stone, of a decision to exclude a pocket of bush that they had given consent to include in the operation.
The EPA said however that the breach wasn't a factor in the cattle deaths.
The Stones' property borders onto the DOC land.
The EPA is recommending a better consultation process for 1080 drops, including providing more clarity for operators and landowners and better mapping.
It wants DOC to provide better information about how 1080 behaves once spread in terms of bioaccumulation and biodegradation.
The EPA also wants improvements to information, particularly for farmers, regarding withholding-periods, caution periods, before cattle are allowed back.
In September 2019, the Stones were critical of the delay the investigation was taking and said they were thinking about taking legal action.
In the months before the 1080 operation, DOC gained permission from the Stones to extend its operation onto 65ha if bush on their land.
Two months after the incident, the EPA decided it was appropriate to independently investigate.