Canterbury farmers are pointing the finger at activist groups - as vandals hit several farms at the weekend.

A farmer in Hororata's looking to replace 30 tires worth $500 each on his irrigation system, after a vandal drilled holes in them.

Meanwhile, at a dairy farm in Leeston, someone's turned on a tap of a vat - draining more than 50,000 litres of milk.

Federated Farmers dairy spokesperson, Chris Lewis, suspects the incidents might be linked.

"Unless they're pretty sick and mindless and think it's a big joke, obviously it's very targeted."

Lewis said some people might think terrorising people and vandalising their gear is the new way of getting their message across.

"People who think of themselves as green environmentalists turn themselves into vandalists".