Wheat rust diseases remain a constant but neglected threat

13 June 2013 – FAO is calling for countries in the global ‘wheat belt’ to step up monitoring and prevention for wheat rusts – fungal diseases that do especially well in particularly wet seasons. Yields could be affected across North Africa, the Middle East into West and South Asia, which account for more than 30 percent of global wheat output and nearly 40 percent of total land area dedicated to wheat planting.

“The favourable 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,” says Fazil Dusunceli, Agriculture Officer in FAO’s Plant Production and Protection Division, a specialist in wheat rusts.

"The ideal approach to prevent the rusts is to grow the right cultivars which are resistant to rust diseases. This minimizes the disease risks. In case of sudden epidemics, fungicide sprays can help to mitigate the effects of the disease, but only if they are caught at an early stage,” Dusunceli adds.

Wheat rusts manifest themselves as yellow, blackish or brown colored blisters that form on wheat leaves and stems, full of millions of spores. These spores, similar in appearance to rust, infect the plant tissues, hindering photosynthesis and decreasing the crop’s ability to produce grain.

Imminent risk still in East Africa, highland areas

Dusunceli underlines that monitoring and surveillance should be stepped up for rusts especially in East Africa in Ethiopia and Kenya, where the growing season is underway and rains have been favourable. If wheat rusts strike on susceptible varieties at an early stage, he said, almost the entire crop can be lost.

“Although in lowlands in warmer areas the crop has fully matured or has been harvested, in highland areas and more mountainous regions, including Central and West Asia, there is still a risk of outbreaks, but there is still time to reduce the losses from yellow rust especially,” Dusunceli notes, since the crops at higher altitudes and lower temperatures are still maturing.

According to a joint alert on www.rusttracker.org issued by the International Maize and Wheat Improvement Center (CIMMYT) and the International Center for Agricultural Research in the Dry Areas (ICARDA), both FAO partners, “Conducive climatic conditions for rusts, especially yellow rust, are resulting in potentially serious outbreaks in the CWANA [Central and West Asia and North Africa] region. Cool and wet conditions have persisted in many countries from Morocco to Bhutan.”

According to the report, especially yellow (stripe) rust has been damaging on susceptible varieties in some parts of Afghanistan, Azerbaijan, India, Iran, Iraq, Morocco, Pakistan, Turkey and Uzbekistan. A widespread epidemic similar to one in 2010 has nevertheless not occurred, thanks partly to the progressive introduction of resistant cultivars, chemical control and warming weather conditions.

However, in some locations disease severities increased to high levels requiring fungicide applications.

In Pakistan, there was a marked increase in reports of high (above 40 percent) and moderate (above 20 percent) severity for all three types of rust diseases, but the effects of yellow rust were most pronounced, appearing in 53% of the surveyed fields.

In Afghanistan, yellow rust appeared in the East, North and Northeast zones at the end of March. Incidence and severity increased on susceptible crops until the last week of April, but warmer weather is expected to curtail further disease spread.

In Morocco, stripe rust was widespread in almost in all areas: 40% of fields surveyed registered a 50% or more severity, requiring fungicide applications.

Prevention, early warning and rapid response key

Using resistant cultivars and early intervention are the key principles of controlling wheat rust diseases, but monitoring for rusts on the ground is typically weak and likewise the reporting times are slow in many countries.

In an effort to cut reporting times, Dusunceli says, FAO recently launched a pilot mobile phone surveillance system in Turkey, using smart phone and SMS reporting technology. A key point is the fact that the task of reporting has been assigned to agricultural extension officers, who in their daily work would normally be visiting wheat fields in each district on a regular basis.

“The information is now instantaneous,” says Dusunceli, “and it is now funneled directly into a database housed in the Agriculture Ministry. That data will give institutions the knowledge and early warning signs needed to react quickly.”

Wheat Rust Disease Global Programme and partnerships

FAO has been running a global programme since 2008 to provide policy and technical support to the concerned countries in collaboration with CIMMYT, ICARDA, IFAD and Cornell University in the context of the Borlaug Global Rust Initiative. Emphasis is placed on prevention, by encouraging the development and planting of resistant cultivars, use of certified seed, rapid seed multiplication, training of farmers, strengthening surveillance and emergency response capacities and international cooperation.

Wheat rusts, like other pathogens, over time can evolve into new strains that are more virulent and damaging to wheat crops. Ug99 is one such strain of stem rust, which emerged in Uganda in 1998-1999. It has since spread beyond East Africa as far as Iran and the worry is that most of the wheat varieties across nearly the same swath of East Africa, West and South Asia are susceptible to this virulent strain. Similarly the Yr 27 virulent strain of yellow rust caused significant losses across the same region from North Africa into West and South Asia during the serious epidemics in 2009 and 2010.

Wheat rusts must be closely monitored as part of a global collective effort. To achieve sustained and improved productivity in wheat, increased investments are needed to support regional and international collaboration efforts to support integrated disease management in the regions often at risk of wheat rust epidemics, specifically in East and North Africa, the Near East and Central and South Asia.