Offenders have targeted fuel and equipment on farming properties in the Clutha and Gore districts.
In a statement, Sergeant Tim Coudret, of Southern District Police, said he wanted people to help police by reporting suspicious behaviour.
"If you see something, say something.
"Look around you and let us know if you notice something, or someone, out of the ordinary."
Suspicious or illegal activity should be reported by calling 111 immediately, if it was happening now, or via 105 if it was afterwards.
"Update your inventory of farm equipment, including model and serial numbers.
"Lock up, even if you’re still on the property, and call 111
if you see something happening."
There were crime prevention actions people could take to secure homes and buildings, Sgt Coudret said.
He recommended people keep an eye out, reduce the risk of theft, keep in touch with neighbours and report anything suspicious.
"If it looks dodgy, it probably is dodgy. No matter how minor, we want to know."
