Steep declines in many Asian currencies against the U.S. dollar mean that food importers in the region are unable to reap the benefits of benchmark grain and oilseed prices that have plunged to multi-year lows in recent months on U.S. exchanges.
Weaker local currencies are slowing demand for wheat, corn and soybeans as price-sensitive Asian buyers make only hand-to-mouth purchases, taking fewer cargoes even as global production hits record highs.
Japan, the world's top corn importer, has seen the yen drop around 14 percent against the greenback since September, while the rupiah in Indonesia, Asia's biggest wheat buyer, has lost about 11 percent.
"Overall there is a feeling of bearishness (on market prices), but when importers look at prices in their domestic currencies, it is not the same as they are still paying more," said a grains trader who declined to be identified.
"The buyer is not covering longer-term and this is really bearish for prices as exporters will end up with large unsold stockpiles."
World corn output is estimated at a historic high of 991.3 million tonnes in the year 2014/15, the U.S. Department of Agriculture has said.
Chicago wheat futures have gained just 2 percent in dollar terms since lows marked in October, while in rupiah value the market is up 10 percent.
Corn has risen 30 percent in yen terms during that period, although the market is up 19 percent in dollar value. Despite these gains, corn prices are less than half their 2013 high of $8 a bushel.
U.S. dollar strength is also causing a shift in trade flows across Asia.
"Even Thailand and the Philippines which are dedicated importers of U.S. wheat have reduced purchases and are looking at other origins," said a second trader.
"The U.S. share is gradually decreasing in the Japanese market because the higher dollar is eroding its competitiveness," said Nobuyuki Chino, who runs trading firm Continental Rice Corporation in Tokyo.
"In 2014, 80 percent of corn came from the United States, but in 2015 I expect the U.S. share to drop to 70 percent."