Yes, a farmer has a simple duty under the Health and Safety in Employment Act (HSE Act) to warn authorised visitors of any work-related, out-of-the-ordinary hazards that may cause them serious harm.

A farmer is not required to warn visitors about natural hazards on the farm, such as bluffs, landslides, rivers, swamps or wasp nests. Nor is the farmer required to warn visitors about hazards from normal every-day farming activities.

Unauthorised Visitors
A farmer is not liable if anyone comes on to their land without permission and suffers harm, whether from a work-related hazard or for any other reason.

Authorised Visitors
A farmer is not liable for any injury to an authorised visitor, as long as the farmer has warned the visitor of any hazards arising from work on the farm, which the farmer knows could harm that person, and which a visitor wouldn't normally expect to encounter. For example, hazards arising from tree felling, blasting, earthmoving machinery or pest control operations.

An authorised visitor is anyone who comes on to a farm with the farmer's express permission and includes people who come for leisure or recreation. It also includes people who are legally authorised to be on the property, but only where they have given the farmer oral notice of their visit. Such people include employees of TransPower, Department of Conservation and local authorities.

A farmer need only give a verbal warning about the hazard, at the time they grant permission to go on the land. If a group of people is involved, it's sufficient to give the warning to a representative of that group.

Paying Customers
The duty changes if people pay to use a farmer's land for any purpose, or are there to inspect goods offered for sale. In this case the people become customers, and the farmer has a full duty to take all practicable steps to ensure that they are not harmed by any hazard arising on the farm. Examples are where people pay to use the farmer's land for camping, horse trekking or fruit picking, or where a tour operator pays for tourists to visit a scenic site on the farmer's land.

Other Persons
A farmer also has a full duty to others such as employees, contractors and persons who are in the vicinity of work taking place. But the farmer is only responsible for hazards within their control.