But two weeks ago, Cyclone Nargis did away with all that. The storm’s timing could not have been worse. Tens of thousands of farm families lost their draft animals, their rice stocks and their planting seeds. Now the harvest is in doubt as well.

“I think we’re going to miss it, we’re going to miss the harvest,” said Hakan Tongul, deputy country director for the World Food Program in Myanmar. “Time is short.”

Mr. Tongul and other international aid experts with long experience in Myanmar fear the cyclone has disrupted the seasonal cycle of life in the Irrawaddy Delta, once one of the world’s most fertile and important rice-growing regions.

Delta farmers lost 149,000 water buffaloes, said Brian Agland, the country director for CARE, and it will be impossible to replace them in time for the plowing season. Instead, CARE and other aid groups will likely be buying what the locals call “iron buffaloes” — small red tractors made in China that go for about $1,000 apiece.

Huge deliveries of new rice seeds are needed, too. Thailand is the likely source for new seeds, Traditionally, delta farmers have used seeds from the rice they grew the year before.

New livestock — pigs, ducks, chickens and fish fingerlings in addition to buffaloes — and seeds are among the priority items for aid groups working in rural development in the delta. “The agricultural cycle is so critical,” Mr. Agland said Thursday. “We’ve got to avoid a hunger gap, and we’ve got very little time.”

On Thursday, the government’s count of the dead rose nearly 5,000, to more than 43,000, with 27,838 missing, The Associated Press reported. The International Federation of Red Cross and Red Crescent Societies has estimated the death toll at between 68,833 and 127,990, The A.P. said.

United Nations agencies and international relief groups held an emergency, closed meeting Thursday afternoon to plot strategies for getting the delta farmers back to their farms and back to work

“They’re restricting, they’re hiding, they’re not allowing us to import, almost nothing,” Mr. Tongul said. “I need 50,000 tons of rice to feed people for the next six months. I’ve got 3,000 on hand. This is what keeps me awake at night.”

Many delta farm families who have lost their homes and livelihoods have sought shelter in Buddhist monasteries, old buildings or schools.

The government has been trucking internally displaced persons to military-run refugee settlements far from their farms. The farmers, the aid agencies say, need to get back to whatever is left of their farms in order to rebuild houses — even rudimentary ones — drain waterlogged paddies, and get on with the plowing-and-planting schedule.

Unless they can do that work, international aid groups in Myanmar say the country will need another 50,000 tons of rice six months from now, Mr. Tongul said.

The Yangon River, which was blocked by sunken ships and storm debris, finally reopened Thursday afternoon, an encouraging development for relief officials. It means that larger shipments — especially of rice — can now be delivered by boat into the port at Yangon if the government loosens its restrictions on imports.

The World Food Program got thousands of high-energy biscuits into the south, but the agency has heard that some of the biscuits have been stolen, or replaced with cheap crackers. , Mr. Tongul said. He said that the United Nations has launched an investigation into the matter.

On Thursday, The A. P. reported, Myanmar’s junta warned in a state radio address that legal action would be taken against people who trade, hoard or misuse international aid for cyclone survivors.

Heavy rains continued to drench Yangon and the delta Thursday, further complicating aid deliveries as bridges and roads wash out. Trucks have so far been used to get most of the aid from the capital region to the delta, and groups like Save the Children, World Vision and CARE have had some success in delivering food into the south.

But many townships and villages deep in the delta are still largely out of contact, and it is likely the death toll will jump once counts in those areas can be taken, regional experts say.

“We’ve been using small boats and motorbikes to get to places,” Mr. Agland said, “and we’re finding villages where 200 people used to live, and now there’s 5 or 10.”

Missing, Mr. Agland cautioned, did not necessarily mean dead.

“For example, there have been a lot of lost kids reported, but we’re also finding groups of kids on their own” in rural, storm-damaged areas, he said.

“The death toll is quite high, and I don’t know if we’ll ever find out the real number. The focus now is stopping more deaths, and keeping the number from growing.”