Crop theft has long plagued San Diego's individual growers, but agriculture experts say all farmers could suffer losses if produce stolen from areas quarantined for Mediterranean fruit flies undermines efforts to contain the pest.

Fruit and vegetables stolen from farms during the night are often scattered around the region by morning, sold at unlicensed roadside stands or under the table to retailers, law enforcement officials said. If contaminated produce is moved outside the county's two quarantined areas, it could lead to a wide-spread Medfly infestation that agriculture officials say could cost the state $1.8 billion annually in lost crops, lost jobs and trade restrictions.

"Fruit theft is an ongoing problem; it happens every year, we hear about it all the time," said Eric Larson, executive director of San Diego County Farm Bureau. "But now we have Medfly, so instead of the potential victim just being the grower, the whole growing community is victimized if the fruit gets scattered and the flies spread."

State and federal agriculture officials quarantined 79 square miles in Fallbrook in November after agriculture officials discovered flies in area traps. Escondido's quarantine began in September after officials found flies, and that area was expanded when other flies were discovered outside its boundaries in December. The now 148-square-mile quarantine covers most of Escondido.

The quarantines restrict the movement of more than 260 fruits and vegetables from areas potentially affected by the flies, which can travel roughly 4 1/2 miles in their lifetime. While the quarantine is in effect, no one ---- not even home gardeners ---- is allowed to transport fruits or vegetables from property inside the boundaries until the produce has been treated and certified by county officials as safe to move and sell.

State agriculture officials said crop theft is a threat to Medfly eradication, but stopping it is not within the California Department of Food and Agriculture's purview.

"The responsibility for crop theft actually falls to law enforcement," said department spokesman Steve Lyle. "CDFA is concerned with any crop movement that occurs outside quarantine regulations. The risk of spread of any invasive species, including Medfly, increases with the frequency of illegal crop movement of all sorts."    

Fruit and vegetable theft in the county is difficult to quantify because partial crop losses are hard to estimate and proving theft is often as complicated as actually capturing criminals, law enforcement officials said. But farmers and law enforcement officials agree that it's a persistent problem.

"It happens every year," Escondido grower Chuck Hoppes said. "People steal from me, they steal from my neighbors. They got so bold last year they even went into the back yard."

Hoppes said he thinks the thieves are bold because they are confident that they won't be caught.

"I never call (police) because what are they going to do?" Hoppes asked rhetorically. "I mean, how do you lift fingerprints?"

"These are really hard crimes to prosecute," Deputy District Attorney Elisabeth Silva said of crop thefts. "If a load of avocados leaves the grove, it can be hard to prove that it was stolen and not picked."

Farmers can best protect themselves from theft with preventative measures such as building fences and planting thorny bushes around groves, said Jackie Cruz, a crime-prevention specialist with the San Diego County Sheriff's Department. Growers should also monitor groves daily and report any theft.

County agriculture commissioner Bob Atkins said additional fly discoveries such as the December capture outside Escondido suggest fruit is being moved from quarantined areas illegally, but he said the bigger problem is probably ignorance, not theft.

"When we’re talking fruit theft, it’s probably people who are going to do it commercially either on the street corner or packing shed and now you can't do that without documentation," Atkins said. "It can happen; I just don’t think it’s one of the biggest issues."

Hoppes agreed that theft might not be the biggest threat to the eradication effort, but said it's still a threat.

"Holes need to be plugged there," he said. "With this situation, it’s interesting how everything compounds."

Contact staff writer Morgan Cook at 760-740-3516.