A Canterbury irrigation specialist fears the thieves targeting large pivot irrigators for their copper wiring may end up getting themselves killed.

Farms with pivot irrigators across Canterbury have been targeted by thieves stripping copper wire from the expensive equipment to sell.

The large irrigators worth thousands of dollars, run on three-phase 400 volt power, with the cables targeted by thieves found on the tallest part of the machine - about 3 to 4 metres above the air.

Irrigation specialist Waterforce's Rangiora branch manager Andrew Panasiuk said the thefts were a relatively new development but had been happening on and off since December last year - police were aware and looking into it.

He said many of the irrigators are operated remotely or on automatic timers - meaning there's no warning before they turn on or move.

"We're now entering a phase where the machines are running and if these thieves continue, they're gonna get a shock - literally - and you know someone could get killed.

"They're taking their lives into their own hands. They're walking out on these machines 3 or 4 metres above the air - presumably in the dark.

"It's very dangerous the work that they're doing. Like I say, it's very easy for someone to get killed with this voltage we're that we're talking."

One farmer RNZ spoke to, who didn't want to be named, said he felt "anxious" and "angry" over the thefts.

Having been targeted himself, he said it was frustrating. He was still working with making an insurance claim so didn't know the final cost of the repairs.

"They're integral to what we do," he said.

"The inconvenience is one factor, the cost of replacing the cable is another.

"But the real problem for us looms in the fact that here in Canterbury we simply can't grow grass through summer if these irrigators aren't running every day."

The farmer said other input costs for fuel and fertiliser had already increased, and feed was likely to too with El Niño conditions looming. He said this put margins under further pressure.

He'd increased security measures on farm, and was talking to other neighbours as well as police about the incident.

"We're just going to have to make it as hard as possible."

Panasiuk said it was an expensive process repairing the damage - not just for the replacement costs, but also labour and down time while the irrigator is out of action.

For farmers, he said it was worth checking irrigators they haven't used in a while - and they should consider having an anti-theft system turned on.

"A lot of these sites are quite remote. We have seen a good number of these sites accessible from public land - so roads that back onto farms."

He urged farmers to stay vigilant and report any thefts to police.

"These lowlives are around and they are targeting these machines.