BRUSSELS — Europe's farmers are staring at their fields and worrying that with people confined to their homes, and their home countries, crops may wither on the vine this year.

Farms across Western Europe are deeply dependent on Eastern Europeans who travel for work during the growing season. Yet with lockdowns in place as agriculture wakes up from its winter slumber, German asparagus may start rotting in the field and French strawberries may suffer from a lack of tending.

European countries say they have enough food, for now. But there are concerns about what could happen if the crisis drags deep into the growing season, as well as fears for the livelihoods of their farmers.

Some countries are trying to mobilize their own citizens into the fields — even those whose ordinary jobs involve little dirt under the fingernails. German leaders set up a vast database to try to encourage students and teachers to go rescue the asparagus crop, which usually starts hitting stores in the second half of April. French leaders have called for furloughed city dwellers to head to the countryside.

“Work in the fields has to be done, and for it to be done, there’s a need for manpower,” French Agriculture Minister Didier Guillaume said last week, declaring a “need for national solidarity so that we can all eat.”

He said French farms were missing 200,000 workers, and he asked “waitstaff in restaurants, receptionists in hotels, hairdressers and those who aren’t active anymore” to sign up for farm duty. “A shadow army,” he called it.

German, Spanish, Belgian, Italian and British authorities have issued similar calls.

Under normal circumstances, workers can crisscross the European Union with nary a passport check, and citizens can work in any European Union country without special permits. But in the era of the coronavirus, nation-states suddenly matter again. Most E.U. nations have asked their citizens to stay at home, border checks have been resurrected, and nonresidents have been barred from many territories.

Food experts and policymakers say the biggest immediate challenges to food supplies are related to the barriers that are now making it hard for produce to reach grocery stores — not growing the food in the first place. And they say that globally, there will probably be enough food for everyone this year, even if production takes a hit in certain regions. But they warn that the decisions leaders are making about closing borders and restricting movement could hit a fragile system.

“As countries combat the coronavirus pandemic, they must also make every effort to keep the gears of their food supply chains moving,” U.N. food chief Qu Dongyu said Monday. “Restricting trade is not only unnecessary, it would hurt producers and consumers and even create panic in the markets.”

The E.U.’s executive branch, the European Commission, has urged member states to treat seasonal laborers as critical workers. But the commission doesn’t have the power to override national policies.

In Germany, authorities have banned seasonal workers over fears they would bring the coronavirus with them. The impact of that decision is being felt on Udo Hertlein’s farm in Bavaria, where white asparagus stalks are starting to peek out of long rows of deep, piled earth, heralding the beginning of spring. Germany prides itself in its delicate white asparagus, and restaurant menus are given over to white stalks with ham, hollandaise sauce and butter potatoes from late April until June. But the Romanian field hands who typically help harvest the asparagus can’t get into the country.

Hertlein said he’s desperately looking for help and has posted ads with farming associations, with job agencies that connect employers to asylum seekers or unemployed locals, and on a new German government website.

That site, which launched last week, has already attracted more than 41,000 listings from farmers seeking help and workers offering their services. But the German Ministry for Food and Agriculture estimates there are 300,000 missing farmworkers in Germany right now. And there is little certainty about whether they can get enough people in the field.

Among those who have posted on the government site in search of work is Wolfgang Grabis, a 58-year-old Berliner who usually earns money transporting art for the city’s galleries, which are now closed.

“I’m a very flexible person,” said Grabis. “Work is there to be done,” he said. “It doesn’t matter what kind it is.”

Hertlein said he’d be open to temporary workers without farm experience.

“If they can fill in for one or two months, we’ll definitely hire them,” Hertlein said. He said he could delay harvesting the asparagus for a while by leaving in place a protective layer of foil. But the season comes to a halt by the end of June.

In France, a government-supported online jobs board lists requests for tractor drivers, wine growers, cheesemakers, carrot sorters, tree planters and more — most with job start dates that are “as soon as possible.”

“Everything is bit messy now,” said Olivier Dumont, a farmer in southern France who grows lettuce, peaches, strawberries and 10 kinds of apricots. “For those whose paperwork was not completed before the confinement started, they are stuck in their countries.” He said he was missing about a quarter of his workers.

Across a newly relevant border in southern Belgium, Stéphane Longlune, 52, who grows asparagus, tomatoes and strawberries, said four of the five Romanian field hands he had hired this season had gotten tangled up with border issues this month and were still at home in Romania. Usually he has six workers during harvesting season, which began last week, he said. Now he has half that.

“I should be able to sell my products, but the real problem is having enough workers,” he said.

With restaurants closed under coronavirus restrictions, European farmers may be able to divert some of their produce into supermarkets, helping to avert potential shortages. But that requires inventing new customers on the fly — and it also depends on workers in the fields.

Policymakers said they were concerned that even local workers were staying home because of illness or fears about developing covid-19.

“If some Belgian workers are confining themselves, are sick or cannot show up to work, it already represents up to 15 percent of the workforce of some sectors,” said Willy Borsus, the vice president of Belgium’s French-speaking Wallonia region, who is the top official for agriculture and economic issues there.

Italy, with the worst health crisis, may also face the biggest farming challenges. The country’s largest agriculture association, Coldiretti, has been issuing dire warnings about the state of crops. About 370,000 workers travel to Italy every year to help with agriculture, the association said, representing about a quarter of all the manpower poured into the fields. Italian authorities have intervened to allow workers who are currently inside the country to stay longer. And they have relaxed other regulations to make it easier for the extended families of farmers to work together on the fields.

The association warned in a statement: “The risk is that the European Union will lose food self-sufficiency this year and its role as the world’s leading exporter of food.”

Luisa Beck in Berlin contributed to this report.