Farm workers to pressure Stop & Shop

Since the Coalition of Immokalee Workers started campaigning for better wages and work conditions a decade ago, nine major food industry buyers — including McDonald’s Corp., Burger King Corp., Subway, and Whole Foods Market Inc. — have agreed to pay an extra penny per pound for tomatoes purchased from Florida tomato growers.

The farm workers are now touring five Northeast cities to visit large supermarkets, which they say contribute to low wages and poor working conditions on farms by using their bulk-purchasing power to drive down prices.

Stop & Shop, owned by Quincy-based Ahold USA, operates 130 stores in Massachusetts, and is one of four major chains — Ahold-owned Giant Supermarkets, Trader Joe’s Co., and Publix Super Markets Inc. — that the farm workers plan to target on their tour.

On Sunday, the farm workers said they were expecting 500 people to march from the Copley Square Stop & Shop at 1 p.m. to the Brigham Circle Stop & Shop.

“What we need is the voices of the supermarket industry committing to change things in a concrete way with the workers,’’ said Geraldo Reyes, a farm worker and organizer with the coalition, which launched the Fair Food Program, a social responsibility operation involving growers, buyers, and farm workers in an independent audit system that monitors labor conditions on Florida tomato farms.

Florida farmers lead the nation’s tomato industry, accounting for $520 million of the $1.3 billion industry. Yet farm laborers are among the lowest-paid workers in the United States, earning on average, an estimated $10,000 to $12,000 a year.

But if buyers agree to the penny price increase, it could add thousands of dollars to workers’ incomes. (Tomato prices fluctuate often because of a number of factors, including weather.)

If Stop & Shop signs on, it will purchase tomatoes exclusively from growers who follow the coalition’s code of conduct, which guarantees improved workplace rights and includes a zero-tolerance policy on forced and child labor.

A Stop & Shop spokeswoman said the workers should target growers — not supermarkets — for increased wages.

“It’s not our place to enter into direct wage negotiations with employees of our suppliers,’’ said Suzi Robinson of Stop & Shop’s New England Division. “We work with thousands of suppliers and it’s a basic business principle that we have to apply.’’

Still, Stop & Shop representatives met with the farm workers last year to learn about the conditions on Florida tomato farms and later adjusted their purchasing to only buy from tomato growers that complied with company standards.

Ahold USA says it requires that its suppliers treat employees fairly and to not employ forced or child labor.

Eve Weinbaum, director of the Labor Relations and Research Center at the University of Massachusetts Amherst, said even though Stop & Shop adjusted its purchasing procedures, it is still important it participate in the farm workers’ program because it establishes industry-wide standards for improved conditions.

“The only way conditions can get better in the field is if the whole industry agrees to play by the same rules. Otherwise, you have a race to the bottom for the cheapest labor, and the worst working conditions are rewarded,’’ Weinbaum said.

Whole Foods Market joined the program in 2008, becoming the only supermarket chain agreeing to the farm workers’ purchasing guidelines and paying the additional penny per pound for tomatoes.

“The agreement has allowed us to sell Florida tomatoes knowing that we have responsible, transparent sourcing in place,’’ said Karen Christensen, a regional vice president at Whole Foods.

Since the Fair Food program started, farm workers say their working conditions have improved considerably.

Workers can take breaks under shade on extremely hot days, a benefit that is not required by law and in the past was not allowed by farm managers.

“When it comes to the agricultural industry, this program brings changes that entitle workers to new rights that never existed before,’’ Reyes said.