Beekeepers on New South Wales' far south coast say a poison attack has caused a major blow to their livelihoods.

Police say 750 hives worth an estimated $150,000 were sprayed with an unknown poison on three properties at Batemans Bay.

The damage was reported to police by beekeepers on Monday.

Police say most of the bees in the hives died in the attack, and the honey was also rendered inedible.

Beekeeper John Casey says more than 200 hives were destroyed on his land and the attack is a major blow to his livelihood.

"You have to start again. You have to make up new material and start from scratch again, or buy bees in," he said.

Mr Casey says the loss will affect production for at least a year.

"Heaps of dead bees out the front of the hives and all over the ground, and there's about nine bee farmers that have had bees destroyed by it," he said.

"We'll start in about five weeks time to go to Mildura and the almonds, which means a loss of income, and you've got to suffer the loss of income off the honey production then."

He says it appears a pesticide was used, but the state's Environmental Protection Authority (EPA) is carrying out tests on the land to confirm what poison was used.

Anyone with information is asked to call Batemans Bay Police Station or Crime Stoppers on 1800 333 000.