KANSAS CITY — Many farmers in the United States have sprayed their wheat crops with fungicide to help protect their stands from diseases such as rust that may thrive during wet years, but producers in less developed parts of the world are being urged to step up their vigilance.
The Food and Agriculture Organization of the United Nations (F.A.O.) warned that wheat yields in North Africa, the Middle East, West and South Asia, where 30% of global wheat output is concentrated, may be negatively affected by wheat rusts during the currently wetter-than-average growing season.
“The favorable growing conditions for wheat are also good for the rust diseases that affect wheat, so when there is good precipitation for wheat, that is also when wheat rusts will be able to best thrive and proliferate,” said Fazil Dusunceli, a specialist in wheat rusts in the F.A.O.’s plant production and protection division.
The most recent Weekly Weather and Crop Bulletin from the U.S. Department of Agriculture highlighted the occurrence of notable precipitation in the Middle East and monsoon conditions in Central India and other parts of South Asia.
Mr. Dusunceli added that prevention in the form of rust-resistant cultivars was the best approach because fungicide sprays may mitigate the disease effects, but only if they are caught early.
He said monitoring and surveillance needed to be increased especially in eastern African countries such as Ethiopia and Kenya, where favorable rains likely have increased the presence of rust diseases, which may wipe out an entire crop if they attack in early stages of the growing season.
Reports of potentially serious outbreaks of yellow rust have been made in Central and West Asia and North Africa.
“Cool and wet conditions have persisted in many countries from Morocco to Bhutan,” said the International Maize and Wheat Improvement Center and the International Center for Agricultural Research in the Dry Areas, both F.A.O. partners.
Yellow (stripe) rust has been reported on susceptible varieties in parts of Afghanistan, Azerbaijan, India, Iran, Iraq, Morocco, Pakistan, Turkey and Uzbekistan. Unlike in 2010, a widespread epidemic has been avoided because of the introduction of resistant cultivars, chemical control and warming weather, the F.A.O. said.
Despite these factors, monitoring for rusts in some countries is typically weak and reporting times are slow. In an effort to cut reporting times, the F.A.O. recently launched a pilot mobile phone surveillance system in Turkey.
“The information is now instantaneous,” Mr. Dusunceli said, “and it is now funneled directly into a database housed in the Agriculture Ministry.”
Wheat rusts manifest as yellow, blackish or brown colored blisters on whet leaves and stems, containing millions of spores. These spores infect the plant tissues and hinder photosynthesis.
Over time, wheat rusts may evolve into new strains that are more virulent and damaging to wheat crops, the F.A.O. said.