Thefts from South West farms cost £8.3m
Thefts from farms in Cornwall, Devon and Somerset cost £8.3m in 2010, insurer NFU Mutual says.
In its rural crime survey, the theft of power tools - such as chainsaws, electric drills and lawnmowers - topped the list of items targeted, it said.
Quad bikes came second, followed by fuel such as diesel and heating oil.
It added that the results showed the countryside continued to be difficult to police and attitudes towards security sometimes remained relaxed.
Theft prevention advice
Ken Doig, from the NFU in Bridgwater, Somerset, said: "Highly organised thieves don't just target tractors and farm machinery.
"They can also make money from items like quad bikes and power tools that can be stolen and sold on in the blink of an eye."
Devon and Cornwall Police advises locking or immobilising vehicles and equipment when it is not in use, and avoiding leaving machinery in isolated locations or fields where it could be removed without attracting attention.
Machinery and tools should be kept locked away, but also visibly marked.
Owners should also keep a list of tools, together with serial numbers in case they needed to be identified later, the force added.