SAN DIEGO -- Avocados are a $140 million-a-year crop in San Diego County, but local growers said they also attract thieves. Experts said avocado theft costs county growers $1 million dollars a year.

"It's a significant problem," said Charley Wolk, who's been growing avocados locally for more than 30 years.

Wolk told 10News in the last five years or so, he's seen the crime on a much larger scale.

"It used to be teenagers stealing a box of fruit for date money," he said.

Now, Wolk sees criminals hiring other people to do the illegal picking. Last February, he confronted two men picking avocados in one of the groves he manages. It turns out the men thought they had been hired legally. In fact, they had been hired to steal for a man named Gaspar Lopez, an employee of Wolk's

"If I hadn't stopped them, at the end of the day they'd have had 3,000 pounds of fruit," said Wolk.

Lopez pleaded guilty to felony grand theft on Friday.

Many of the avocado thefts happen at night, usually when there's a full moon for more light, growers said. During the day, thieves tend to hit on rainy days and Sundays. Growers said they choose rainy days because the leaves make less noise and Sundays because there are fewer people in the groves.

There are San Diego County Sheriff's Deputies with special training in dealing with agriculture crime, but it's tough to track. Groves are large and spread over a large area.

Wolk said avocado theft probably doesn't affect what consumers pay at the grocery store because there are plenty of avocados still available. However, the theft is very hard on growers.

"The grower can't take a tax deduction," he said. "He doesn't get anything other than he lost the fruit and lost the revenue."

The sheriff's department told 10News the thefts occur based on the price of the avocados; the higher the price, the more thefts they see.

Authorities said the stolen fruit is typically sold at roadside stands and small markets.