Federated Farmers is calling on farmers to be vigilant following four suspected arson attacks near Ashburton.
The Fire Service says the fires - in trees, hay bales and a paddock - began just after 4am southeast of the South Canterbury town on Saturday.
Grain and seed chair for Federated Farmers mid-Canterbury, David Clark, says the fires are creating needless work for local fire fighters "on needless wanton destruction".
He says such fires could leave the community very vulnerable in a true emergency if resources were tied up or in the wrong location.
Federated Farmers says farmers should watch out for suspicious vehicles and activity, especially at dusk or during the night.