Four months after the first nationwide rules on organic food went into effect, they appear to have made little difference to consumers, retailers and producers.

The U.S. Department of Agriculture regulations — and its green-and-white "USDA organic" seal — were supposed to replace a patchwork of state and industry rules, giving consumers confidence that the food they bought was, in fact, organic.

But shoppers at a Whole Foods store in Maryland recently greeted the seal with a shrug — if they noticed it at all.

Consumer Joan Sechler, who has been buying organic food for about five years, said she has seen the new USDA labels on some produce, such as navel oranges.

But she said California laws were strict enough already.

At the store, bags of baby lettuce and containers of ice cream are labeled by California Certified Organic Farmers. Texas carrots are labeled by Quality Assurance International and Oregon almond butter by Farm Verified Organic.

Other products, such as Horizon Organic low fat organic eggnog, carry the USDA seal, which identified them as "100 percent organic" — containing only organic ingredients — or "organic" — containing at least 95 percent organic ingredients.

Products labeled "made with organic [ingredient]" must be between 70 percent and 95 percent organic and cannot use the USDA seal.

But shopper Ironda Campbell was not aware of the new USDA rules, though she has been buying organic for years. She said she worries about genetically modified food, but that she might not take the new nationwide labeling rules into consideration when buying groceries.

"It would make a difference if they're more stringent," she said.

Whether the new rules have had any effect on sales is difficult to determine. Results from surveys of organic retailers will not be available until late spring, said Katherine DiMatteo, executive director of the Organic Trade Association.

But the changes, which took effect Oct. 21, have made little difference to producers.

"Even if I did decide not to be certified in the future, it would not change my farming practices at all," said Mike Pappas, owner of Eco Farms in Lanham. He is certified because he has to be in order to call his herbs and greens organic, but does not use the USDA seals.

Each certified business can choose whether to use the new USDA seal, the state's seal or no seal, said Valerie Frances, coordinator of the Maryland Organic Certification Advisory Committee of the Maryland Department of Agriculture. She said she did not think any of the around 90 Maryland farmers certified under the USDA's rules were using the new seals.

Since most of the state's farmers sell their products locally, the nationwide seals make more sense for those with national or international markets, she said.

Each ingredient of an organic product must be organic itself.

Therefore, if someone in Maryland wanted to import an ingredient from another state, the ingredient would have to meet Maryland's organic standards. With the new nationwide rules, people no longer have to check the regulations of other states, Frances said.

The main effect of the new rules has been administrative, said Erroll Mattox, who has been an organic farmer in Hebron for nearly a decade.

The rules have not changed the way people farm, but they have changed the business side because they require an "adequately documented history" of what you do, he said. To be certified, farmers' production methods and record keeping must meet requirements set by the USDA.

Pappas said the biggest effect of the new organic rules has not been in the production of food but in its marketing — the word "organic" is now a sales term.

"It's a way for big agribusiness to get into the organic business," he said.

But Campbell wants the labels to mean more than that, because she wants to know what is in her food. As she scooped rice from a bulk bin into a plastic bag one weekday evening, Campbell said she sometimes worries that it is hard to tell exactly what a product contains because of genetically modified technology.

"They're combining fish with tomatoes and doing something with corn," she said.