Among the items disappearing are sheep, The Washington Post reported.
"They want our sheep," said Andrew Allen, 46. He recently lost 45 head of sheep worth more than $6,000.
Allen is one of nearly two-dozen farmers to fall prey to sheep rustlers over the past year.
Insurance and farm unions said the crime wave began when global food prices started rising, the newspaper said. Grain prices have set record highs since 2008 and meat prices, particularly for lamb, also surged.
Because of scaled-back production in places like New Zealand, a farmer now gets about 35 percent more per pound for lamb than in 2008.
"I'd see people parked at the roadside and looking at the lambs, and I'd chat with them, quite proud of the sheep myself," said Paul Taylor, 31. His farm in High Legh, a small village in northwest England, was rustled of 100 sheep worth $16,000. "Nothing is innocent anymore. Now when people drive past, you take their license plate numbers down."
Farmers are also reporting the theft of more machinery. Because the price of grain is at record highs, farmers in Russia and elsewhere are looking to produce more products, opening the door for equipment thieves taking advantage of the situation.
"There is no doubt that this is directly related to food prices," said Tim Price, spokesman for the National Farmers Union Mutual, Britain's largest agricultural insurer. "The prices went up, and so did the thefts."