By Amor Yahyaoui

n Eritrea, farmers face frequent drought but also a rainy season that can produce severe disease incidence in their vital cereal crops. To limit the potential damage they have devised an indigenous method which dovetails neatly into the concept of integrated disease management.
        In 1999 Eritrea, which borders the Red Sea between Egypt and Ethiopia, had the usual low rainfall and early drought. Then in August came humid and warm conditions that enhanced foliar disease development.
        ICARDA observations in fall of 1999 revealed many potentially harmful foliar diseases enjoying optimum conditions for their development. The endemic and most severe cereal diseases were leaf rust (Puccinia recondita) on wheat, as well as a number of foliar diseases on barley. The most severe foliar diseases of barley were found to be net blotch (Pyrenophora teres), spot blotch (Bipolaris sorokiniana), and scald (Rhynchosporium secalis). But not to be outdone, other barley diseases present included bacterial leaf streak (Xanthomonas transluscens) and septoria (Septoria passerinii).
        Left uncontrolled, these diseases hit crop yields badly. However, Eritrean farmers have developed a unique wheat-barley crop mixture called Hanfetse that contributes greatly to the reduction of disease levels.
        Integrated disease management (IDM) programs normally use differing control methods. It is not unusual to find that, although cultural practices, fungicide combinations, multilines, plant population variations, or varietal mixtures are often advocated for disease reduction, farmers in practice seldom use them.
        In Eritrea, however, Hanfetse is commonly used by farmers to deal with both drought and foliar diseases. In dry seasons, the barley in the mixture ensures that some production is obtained even when, as often happens, the wheat fails to grow properly. During rainy seasons the wheat makes use of the moisture and not only gives better yields but also protects the barley, keeping it upright. Invariably, mixing the two shows better yield performance than growing these crops singly. 
        The major benefit comes from the effect on foliar diseases of growing these crops in mixture. In Eritrea, farmers favor bread wheat, but because the available local bread wheat cultivars are so highly susceptible to leaf rust, they can suffer up to 80% loss when grown alone. The local barley cultivars are tall and susceptible to lodging and to many foliar diseases.
        In a Hanfetse crop, lower disease incidence was recorded both on experimental sites and in farmers' fields, and good yields obtained in both cases. Less rust develops on the mixture due to the dilution effect caused by the barley. Rust spores are wind-borne and can spread very rapidly over large areas. When they fall on barley leaves in the mixture, they fail to reproduce and there is a direct reduction of the rust inoculum and consequently a lower infection rate for the wheat plants.

        Likewise, there is a similar effect for barley and its specific foliar diseases such as scald, net and spot blotch. These are stubble-borne and are normally splash-dispersed by wind and rain but over short distances and usually within the primary source of inoculum. However, these pathogens fail to infect wheat plants, bringing another major reduction in inoculum level and in disease incidence. So, both crop species in the mixture are protected from the heavy infection of their respective diseases because the foliar cereal pathogens are highly specific. In other words, a wheat rust pathogen does not infect barley, and barley pathogens do not cause diseases on wheat.
        Hanfetse is widely grown in Eritrea. The mixed grain is used for traditional 'angera,' a flat bread usually made solely from the grain of teff (Eragrostis abyssinica).
        Of course, the technique has its drawbacks as well as further potential. Although total Hanfetse production is adequate compared to that from the individual crop species, its productivity remains very low. A major problem of this mixture system is the wide maturity range in the Hanfetse crop. The wheat cultivars available to the farmers are late whereas the barley cultivars are early maturing. Farmers are obliged to cut the Hanfetse crop when the wheat is still green to avoid over ripening and shattering of barley.
        This useful indigenous knowledge could be exploited and improved with the introduction of new germplasm from the wide range to which ICARDA has access in its gene bank. Plant breeders could help create a De novo Hanfetse crop that mixes hull-less barley with awnless bread wheat. The components of such a blend will have a closer maturity range, better nutritional quality, and higher yield potential.
       In this way Hanfetse will realize its true potential and Eritreans can go on enjoying the delights of angera.

Dr Amor Yahyaoui is Senior Cereal Pathologist at ICARDA.