Mahmoud Solh, director-general of the U.N. International Center for Agricultural Research in the Dry Areas, said the Ug99 strain of wheat fungus, also known as stem rust, could soon affect farms in the Middle East, Central Asia, South Asia and East Asia, IRIN reported Thursday.

Richard Brettell, head of ICARDA's Biodiversity and Integrated Gene Management Program, said the most effective way of controlling the disease is to grow resistant varieties. "The problem is that almost all the wheat varieties grown in West and South Asia are known to be susceptible to Ug99," he told IRIN. "It will take time and coordination to replace them with resistant varieties."

An outbreak of stem rust in North America in the 1950s destroyed up to 40 percent of the spring wheat crop.