This is the VOA Special English Agriculture Report.

Farmers in Afghanistan already struggle with the effects of drought and years of conflict. Now there is worry about a new threat headed in their direction in the wind -- a fungus that destroys wheat crops.

The disease is a form of stem rust named for its discovery in Uganda ten years ago. Ug99 is now in one of Afghanistan's neighbors, Iran. The disease kills wheat plants by robbing them of water and nutrients. Stem rust produces reddish-brown spots on the stems of infected plants. The weakened stems break easily.

The world's last major outbreak of stem rust took place in the nineteen fifties. Agriculture -- excluding opium production -- represents about one-third of the Afghan economy. But agriculture employs eighty percent of the country's workers. And almost all Afghan farmers grow wheat to feed their families or to sell.

Afghanistan has a population estimated at almost thirty-four million people. Mahmoud Solh directs the International Center for Agricultural Research in the Dry Areas, or ICARDA, in Aleppo, Syria. He says it took a few years for Ug99 to show its destructive power.

Then, in Kenya, it destroyed from twenty to eighty percent of wheat crops. And before long, he says, winds carried the disease from Kenya to Ethiopia. Ug99 has also affected Sudan and more recently has moved into Asia, spreading to Yemen and Iran.

Mahmoud Solh says the disease now threatens Afghanistan and South Asia. But he also calls it a global threat to food security. Most of the commercial kinds of wheat are at risk from Ug99, he says. These include varieties grown in the United States, Canada and Europe.

The expert urges Afghan farmers to tell agriculture officials immediately if they suspect stem rust in their fields. He says the fields will be treated to kill the fungus and to stop it from spreading. Farmers will get new seeds that resist Ug99.Researchers have developed these seeds for the conditions in Afghanistan.

Organizations of village farmers are working to expand the supplies of the improved seeds. They are receiving guidance from ICARDA and money from international groups.

The goal is to replace at least ten percent of Afghanistan's wheat fields with the new seeds each year. The effort will begin with areas along the border with Iran.

And that's the VOA Special English Agriculture Report.