A world food supply crisis is leading some African immigrants in the city to send packages of food to family members back home facing rising food prices and empty shelves at the market.

Immigrants from Mali and Senegal in particular have found boxes of rice, sugar, and tomato paste are more appreciated than cash among relatives in their home countries, where the weak dollar now buys less and shortages have driven up the price of staples, particularly rice.

The crisis comes as farmers have begun selling crops to the biofuel programs of developed countries, while developing countries such as India and China have been consuming more rice as they become wealthier. The increasing sources of demand have left other consumers with less and have driven up prices, with the cost of rice increasing by more than 140% in 2008.

“They’re running out of rice and they’re running out of oil,” an immigrant from Dakar, Senegal, who works at the African Services Committee in Harlem, Ndeye Gueye, said.

Ms. Gueye, 26, is helping to provide for two families, her own and that of her husband, chipping in some of her earnings every few months along with other relatives here in New York. They buy 25-pound bags of rice and cans of condensed milk, tomatoes, and other nonperishables that can survive a long ocean journey.

“It may not be all of their nutrition, but it’s a little support,” Ms. Gueye said.

In countries such as Senegal, where traditional fish and peanut stews are served alongside jasmine rice from Thailand, consumers have been experiencing the rising prices for months.

Ms. Gueye’s older sister, Anta, 32, said that when she first sent a package about a year ago, as prices were first beginning to spiral upward, she was nervous about telling the shipper what it was. She told him it was clothing and shoes.

Now, sending dry goods by boat has become normal, she said.

The families buy a space in a container on a ship headed to West Africa for about $120 per 50-pound package, the Gueyes said. The trip takes about three weeks, and sometimes as long as a month.

The housing coordinator at the African Services Center, Aida Diallo-Diagne, said that at least four of her clients from Senegal and Mali have told her they have begun sending food home instead of sending traditional cash remittances.

“We have this extended family, so you have a first cousin, or a brother-in-law, everybody takes a turn,” she said. “If everybody chips in, you can buy a whole lot of rice.”

With the price of rice rising here as well, however, the new system of food remittances is increasing the strain on some families already struggling to provide for their relatives back home.

May Pioe, 34, who works at the Sunugaal Meat Market in Harlem’s Senegalese enclave on West 116th Street, said she is supporting 28 family members in Dakar after being sent to New York at age 13 as a child bride.

“We’re all doing it. There’s no point in sending money because the dollar is so low,” she said.

Ms. Pioe is divorced and has two sons in college, however, and she said the cost of providing for them and for her family in Senegal has become increasingly difficult.

“It’s taking so much out of our lifestyle here,” she said. “But I was a hungry as a child. I know what it feels like to go for three or four days without eating, so that’s what gives you the drive to do it.”

In the Sunugaal Meat Market yesterday, the stacks of 25-pound jasmine rice bags from Thailand stood mostly untouched, however. Most African immigrants, including Ms. Poie, are doing their shopping at wholesale stores like Costco and BJ’s, where prices are lower. But those stores have begun limiting the number of bags of rice shoppers can buy because of concerns about a panic.

A Pace University student and manager at the Senegalese restaurant Africa Kine, Allou Djigal, 34, is among many immigrants, including those from other Equatorial countries affected by the crisis, who say prices are too prohibitive to pay for both the rice and the shipping.

“I’ve heard about it, but it’s not worth it,” he said. “The prices are bad here, too.”

Miriam Bingoura, 50, of West Harlem, who provides for her parents and son in Guinea, said she has been sending rice, pasta, and tomato paste along with clothing and shoes by boat for a few years. She spends about $150 to send a barrel packed full of goods every few months, provisions her family now depends on, she said.

Ms. Bingoura recently stopped working because of an illness, however, and is not sure how she’ll continue to cover costs for herself and her family’s food.

“You come here to help them, but rice costs too much money,” she said.