Sharing experience and approaches
An effective national strategy for combating wheat rust has four key components:
- Surveillance and rapid reaction plans
- Information sharing across countries
- Capacity strengthening – for government officials, extension services and farmers
- Participation in ongoing research programs to develop resistant wheat varieties.
A multi-faceted approach is needed by countries to combat wheat rusts. Immediate action to combat new rust races often means the use of fungicides. Reducing the cropping of susceptible mega-varieties across vast wheat growing areas is perhaps the best insurance policy against widespread rust damage.
Countries can consider policies to plant a range of resistant wheat types in their farming systems – greatly reducing the risk of emerging virulent rust types spreading over the entire area. A long-term plan includes continued investments in crop research. Countries can participate in international research efforts to continually develop wheat varieties that resist rust and other diseases.
Surveillance, preparedness and rapid reaction
Efforts in rust surveillance and research on breeding wheat for rust resistance are being stepped-up across developing countries but much more still needs to be done. Some effective approaches shared by agricultural planners at the ICARDA Symposium include the creation of national and regional wheat rust networks of scientists and agriculture extension specialists to provide early warning and information exchange on rust incidence in their area.
At the global level the Wheat Rust Toolbox created by Aarhus University in Denmark uses geographic information systems technology to map rust types and movements around the world. This data should be shared via the internet and the Rust Spore Global Wheat Rust Monitoring system set up by the FAO and the Borlaug Global Rust Initiative (BGRI).
This is complemented by the Global Rust Reference Laboratory, also at Aarhus, that is establishing itself as the international centre for rust type analysis and research. National and regional rust laboratories need upgraded skills and facilities to provide local early warning services at the field level. These local rapid reaction networks are vital to monitor new rust incidence and test rust races to advise on the spread of the disease and appropriate interventions.
Because rust can cover a lot of ground in 24-48 hours, these local networks are a vital first line of defense. Global databases may be updated several times a month. During certain times of the growing season, local action even requires daily information.
Diversified cropping strategies
Diversified cropping of wheat – avoiding the sowing of mega-varieties across large cropped areas – is another possible defense against wheat rust. In most areas of the Middle East, East Africa and South Asia, farmers have been planting the same varieties for 20-30 years. This practice is not advisable in a situation where the rust races are mutating and new ones are emerging much more rapidly than the past.
As it takes about 10 years to develop a wheat variety with new resistance – and no one knows when and where new rust races will appear – the most effective strategy to combat new rust races is to diversify cropping patterns, and have various types of rust resistant varieties readily available.
In practice, this means that farmers and their extension advisers need to realize that no single variety of wheat should form more than a quarter (or less) of their (or the national) crop.
In many low-income countries, despite growing pressures from rusts and rust epidemics, farmers are still reluctant to move away from the traditional wheat varieties (in some cases 40 years old) that they know and trust. This is because:
- Smallholder farmers are generally risk adverse
- New varieties don’t always meet local farmers’ needs or preferences
- There is limited information on their availability
- There is limited availability or access to seeds of new and resistant varieties.
With surveillance systems and communication of rust alerts must also come capacity strengthening of extension workers and farmers. Both groups need to be aware of the dangers of mega-cropping in today’s new rust environment. This includes being aware of the benefits of using new resistant wheat varieties – that may be new to them but have been tried and tested by researchers and farmers in other regions.
Breeding and seed solutions
Crop research – the breeding of disease-resistant wheat varieties – is the chief line of long-term defence for wheat crops against stripe rust. International efforts to develop new wheat varieties resistant to rusts are spearheaded by agricultural research centers such as ICARDA and CIMMYT, working closely with national research and extension programs and commercial breeders or seed companies. Disease resistance can be built into wheat, but the development cycle is typically about ten years (ten generations of breeding and testing resistance in a new variety) for new varieties to be released and made available to farmers.
Benefits from ‘slow-rusting’ wheat varieties
An alternative approach in wheat breeding is being pursued – breeding and deployment of slow rusting (or durable) adult-plant resistance (APR). This approach allows wheat to grow and yield acceptably alongside rust, with a low level of disease attack and minimal effect on yield and seed quality.
So far, some wheat varieties with various levels of APR to all three rusts have been bred. Progress has been made in understanding the genetic basis and genetic diversity of resistance to stripe, stem and leaf rusts. There is optimism among crop researchers that high-yielding wheat varieties with a high level of resistance to all three rusts could soon be a reality. In fact, triple rust-resistant (APR) varieties are becoming available that have 10-15% higher yields than presently popular varieties.
Use of fungicides
Fungicides can be the first line of defence against new varieties of wheat rust. In wealthier countries, fungicides are used on a large scale as a key part of the national food security strategy.
Lower-income countries cannot always afford the luxury of large-scale chemical treatment of fields affected by rust. But chemical interventions do provide a practical, rapid-response solution, for example, to stop local intrusions of new rust races – giving the authorities time to assess the races and multiply new resistant varieties.
In the high-income countries of Europe, Australia and the Americas, farmers can manage disease pressures in wheat production with fungicide applications. It’s a different story in the developing world. Many countries do not have the right fungicides registered to combat wheat rusts.
The logistical issues faced by low-income countries are how to provide small-scale wheat farmers with the right chemicals, on time and at an affordable cost. Other needs are the necessary sprayers, protective clothing, and knowledge for their use or relevant training. For fungicides to be effective you need information on disease onset to be shared widely and early – surveillance systems are needed.
Despite these hurdles, emergency fungicides are used where possible in developing countries. Examples include Ethiopia in 2010 when 30% of the wheat area was sprayed and over $3 million worth of fungicides were distributed. In Iran fungicides are registered, supplied and regularly used in emergency situations – under rust campaigns directed by the national plant protection organization.