SAN FRANCISCO (AP) — President Barack Obama's proposed budget would eliminate the nation's only program that regularly tests fruits and vegetables for deadly pathogens, leaving public health officials without a crucial tool used to investigate deadly foodborne illness outbreaks.

The budget plan the president sent to Congress Monday would ax the Agriculture Department's tiny Microbiological Data Program, which extensively screens high-risk fresh produce throughout the year for bacteria including salmonella, E. coli and listeria.

If samples are positive, they can trigger nationwide recalls, and keep tainted produce from reaching consumers or grocery store shelves.

Food safety advocates and a top-ranking U.S. Centers for Disease Control and Prevention official said the information also can help pinpoint foods tied to illness outbreaks, and would not easily be replaced by companies' internal tests or more modest federal sampling programs.

"It's the radar gun that keeps the industry honest and if that's eliminated, we don't have a program that will keep the industry in check," said Mike Doyle, director of the University of Georgia's Center for Food Safety, which works with the produce industry to improve safety measures on farms and in packinghouses. "This is really important because you and I eat that food and we don't want to get sick."

White House Office of Management and Budget spokeswoman Meg Reilly said the decision to cut the $5 million program was made after USDA decided it had limited impact. She said it also USDA determined it was not a good fit within its Agricultural Marketing Service division, which is partially funded by fees collected from produce growers.

"While food safety is a vitally important part of successfully marketing produce and other agricultural products, other federal and state public health agencies are better equipped to perform this function," USDA spokeswoman Courtney Rowe said in a statement.

Industry leaders from United Fresh Produce Association and other major trade associations have repeatedly pushed the government in recent years to get rid of the comprehensive testing program, saying it has cost growers millions in produce recalls and unfairly targeted farmers who aren't responsible for contaminating the food. They want the private sector to do more of its own testing, rather than allowing USDA to take random samples of fruits and vegetables at massive grocery store distribution centers, after produce has already left company control.

Last year, for instance, California firms recalled pre-packaged fresh cilantro and bagged spinach from the marketplace after MDP tests of random samples detected salmonella.

According to the CDC, nearly one-third of the major, multistate foodborne illness outbreaks in 2011 were caused by contaminated fruits and vegetables.

The 120,000 food samples the program has collected in the last decade have offered public health officials important clues when they are probing the source of food poisoning outbreaks, Dr. Robert Tauxe, the CDC's top food-germ investigator, said in an interview in October when the agency began offering the program's employees early retirement packages.

Last year, the program found lettuce and spinach contaminated with E. coli O157:H7, the strain most commonly responsible for food poisoning, and also started aggressively testing for listeria in cantaloupes in response to the nation's most deadly foodborne illness outbreak, in which 30 people died after eating listeria-tainted melons. In one instance in the last several years, a contaminated produce sample the program identified was later tied to an illness cluster, Tauxe said.

FDA Produce Safety Staff Director Samir Assar said in an October interview that while his agency also conducts targeted tests of certain high-risk fresh fruits and vegetables each year, cutting MDP would leave the regular testing of sprouts, tomatoes, cantaloupe and cilantro to industry and more modest state and federal efforts.

"I don't think this would be information that would be easy to replace," Tauxe said.

Rowe suggested the Food and Drug Administration, CDC and state agencies should collect similar data, but no agency reported having immediate plans to step in.

Ray Gilmer, a spokesman for the United Fresh Produce Association, said the industry also supported funding FDA to perform scientifically rigorous tests that would help to monitor public health.

FDA spokeswoman Siobhan DeLancey, however, said she could not speculate on whether FDA would set up a parallel program, or had the money to do so.

"We don't test produce," said Lola Russell, a CDC spokeswoman. "That's just not part of our mission."

State health departments are already facing tough choices as they try to come up with enough dollars to keep food safe after tens thousands of employees have been laid off in recent years. And the FDA has always been crunched for food safety dollars, receiving so little money for food inspections that some facilities are only inspected every five to 10 years. A new food safety law President Obama signed last year aims to increase the number of inspections in the United States and abroad, but emphasizes prevention rather than increased testing of foods.

Still, both the industry and government agree that tests alone won't keep the food supply safe from contamination.

Since the 2006 E. coli outbreak in spinach that killed three people and sickened more than 200, growers in California's lush Salinas River Valley have been trying out new farming and testing standards for leafy greens, some of which have since become national guidelines.

Nicknamed "America's Salad Bowl," the area grows much of the nation's lettuce, and the local industry collects reams of data about pathogens to improve their growing practices, said Hank Giclas of the trade association Western Growers.

Half a dozen major shippers are currently pooling their data about leafy greens and may share it with other businesses, the government and academic researchers in the future, Giclas said.

"It's possible that private sector testing could serve as a type of substitute. Industry has shown a willingness to share that information, so those are the kinds of things that we need to talk about," Giclas said.