Undated file photo shows the flowering almond trees on a farm in Modesto, California, the United States. In the US, almonds production is mainly concentrated in California with an output of 916,000 tons in 2011/12, about 11 percent of which were exported to China. (Xinhua)

Workers sort almonds at an almond processing plant in Modesto, California, the United States, on March 19, 2013. In the US, almonds production is mainly concentrated in California with an output of 916,000 tons in 2011/12, about 11 percent of which were exported to China. (Xinhua/Yang Lei)

Farmer Dick Braden walks past facilities at his almond processing plant in Modesto, California, the United States, on March 19, 2013. In the US, almonds production is mainly concentrated in California with an output of 916,000 tons in 2011/12, about 11 percent of which were exported to China. (Xinhua/Yang Lei)

A worker labours in the field on an almond farm in Modesto, California, the United States, on March 19, 2013. In the US, almonds production is mainly concentrated in California with an output of 916,000 tons in 2011/12, about 11 percent of which were exported to China. (Xinhua/Yang Lei)

A farmer displays a green almond on a farm in Modesto, California, the United States, on March 19, 2013. In the US, almonds production is mainly concentrated in California with an output of 916,000 tons in 2011/12, about 11 percent of which were exported to China. (Xinhua/Yang Lei)

Shelled almonds are seen at an almond processing plant in Modesto, California, the United States, on March 19, 2013. In the US, almonds production is mainly concentrated in California with an output of 916,000 tons in 2011/12, about 11 percent of which were exported to China. (Xinhua/Yang Lei)

A worker walks past facilities at an almond processing plant in Modesto, California, the United States, on March 19, 2013. In the US, almonds production is mainly concentrated in California with an output of 916,000 tons in 2011/12, about 11 percent of which were exported to China. (Xinhua/Yang Lei)