Japan's largest technology firms have shut down dozens of factories that produce an array of microchips and consumer electronics products, including computers, cameras and popular smart phones.
"It's a very dire situation right now," Fujitsu spokesman Scott Ikeda said.
Toshiba shares fell 17% on Monday on the Tokyo exchange, while Fujitsu slumped more than 6%.
Among the sectors most affected is the $18-billion market for so-called NAND chips — the small data-storage units that fit into smart phones and tablet computers and allow users to store video, music and photos. Japan, and specifically Toshiba, account for about 35% of the world's production of NAND chips, according to research firm IHS iSuppli.
The chips can be found inside hot consumer devices such as the recent iPad 2 tablet, as well as Apple Inc.'s iPhone and Motorola Inc.'s Droid X smart phone.
"The major impact on Japan's semiconductor production is not likely to be direct damage to production facilities, but disruption to the supply chain," iSuppli analyst Dale Ford said in a note to investors Monday.
Japan's disaster-struck northern region, though relatively undeveloped in terms of industrial production, is one of the nation's leading areas for rice production, and Japan as a whole is one of the world's largest importers of corn and wheat.
Speculation that demand for imported grains would rise in Japan drove up corn, wheat and soybean futures in the U.S.
California Department of Food and Agriculture Secretary Karen Ross said Japan was a key export market for farmers in the state, particularly for specialty crops such as blueberries, cherries and pomegranates. She warned a gathering of grape and fruit growers Monday that the state's farmers probably would see a "disruptive" effect on their business.
There seemed to be a small silver lining in the disaster's aftermath. Oil prices fell slightly over the weekend after a long run-up in the face of unrest in the Middle East.
But concerns grew that the disaster in Japan could drive up fuel prices in the long term, in turn cooling a boom in domestic farm exports.
Stocks fell sharply Monday in Japan, where the Nikkei index slumped 6.2%, compared with only moderate losses in most of the rest of the world.
The Dow Jones industrial average slid almost 150 points early on, but recovered late in the day to close down 51.24 points, or 0.4%, at 11,993.16. Stocks fell 0.9% in Britain, 1.3% in France and 1.7% in Germany. Stocks in Hong Kong rose 0.4%.
Among U.S. companies, luxury goods makers, insurers and utilities tied to the nuclear energy industry were among the losers.
Companies specializing in other forms of energy, such as coal to solar power, were big winners as investors bet that they could gain from a potential backlash against nuclear energy because of the unfolding disaster at the Fukushima reactor.
Insurance stocks fell as investors worried the industry could be on the hook for big payouts.
AIR Worldwide, a disaster research firm, estimated that initial insured property and casualty losses could reach as much as $35 billion. Other analysts put the number at nearly twice that level. Aflac Inc. and Genworth Financial Inc. each fell 3%.
"It will take some time before we have any inkling of how much this will cost," said Sam Stovall, chief investment strategist at Standard & Poor's Corp. "Right now investors are fearing the worst and acting accordingly."
Times staff writers Andrea Chang, Walter Hamilton, P.J. Huffstutter, Hugo Martin and David Sarno contributed to this report.