hen discussion on a crop disease reaches the Prime   Minister's Office, mere concern has turned into a serious problem. So was it with faba bean necrotic yellows virus which was responsible for the devastation of the faba bean production in Egypt in 1992, and again in 1999 for considerable losses.
        However, thanks to collaboration between ICARDA and Egyptian researchers, and financial support from the European Union (EU), hopes are high that the 90% losses will not be repeated and that the Prime Minister can rest easy, at least on this issue of crop protection.

        The joint team of scientists started experiments aimed at finding ways and means to reduce the chances of virus infection of faba bean plants in the field. As there were then no faba bean cultivars resistant to FBNYV infection, experimentation focused on identifying cultural practices that could lead to reduced virus spread. Investigations conducted at Sids Research Station in Middle Egypt for three years (1995-1998) showed that the elimination of virus-infected plants (roguing), by pulling them out by hand, reduced further spread of the virus inside the field. This was because, after arriving in the host crop, the aphids colonize the plants and breed. The subsequent generations pick up the virus from the infected plants, if it is still present, and continue the spread of infection as they move around between plants.
        In addition, the scientists evaluated different sowing dates. It was found that a delay (10-15 days) in sowing the crop until early November led to reduced virus spread. Infection was still present at low levels but the peak of aphid movement was taking place before the plants were fully developed as attractive hosts. Early October planting, by comparison, led to heavy infection levels three to four weeks after aphids flew into the newly-emerged crop.
        Since virus infection is brought into the faba bean crop through aphids, experiments were also conducted to find out what was the minimum number of pesticide sprays necessary and at what growth stage they should be applied to reduce virus spread. Two sprays with the systemic aphicide pirimicarb at a concentration of 0.2%  (Pirimor) in December and January gave a significant reduction in FBNYV spread.
        Alternatively, and based on experimentation at ICARDA research station at Tel Hadya, Aleppo, Syria, it was demonstrated that when faba bean seeds were coated with imidacloprid (Gaucho) at the rate of 2 g per kg of seeds, FBNYV spread was reduced from 28% in plots with untreated seed to 1.6% in plots with treated seeds. Seed treatment with an appropriate pesticide is less costly than pesticide sprays, and can provide protection for up to two months and is less likely to harm beneficial insects.
        However, since the level of infection varies from year-to-year depending on the extent of the inoculum pool and on the weather-dependent activity of aphids, the insurance of a seed treatment may not be the best route for many farmers who prefer a wait-and-see approach. The collaborating scientists have shown it is possible to bring virus infection down from the 70-80% level to just 5-10% by integrating mid-November sowing with the early removal of any virus-infected plants,

        Faba bean is the major food legume crop in Egypt, and its dry grain provides the main source of protein for most of the population. Grain production is affected by a number of diseases caused by either fungi or viruses, but in 1992 local advisers were puzzled by a new disease which was decimating plants, particularly in Middle Egypt. The ICARDA plant virologist, who was attending a conference in the country, was able to visit affected fields and take samples of infected plants. These showed the cause was a virus not previously identified in Egypt. Young leaves of infected plants showed interveinal chlorosis and yellowing, and were cupped upward. When infection occurred early in the season, faba bean plants were severely stunted and killed prematurely.
        Further sampling in 1993 confirmed that faba bean necrotic yellows virus (FBNYV) was indeed the culprit, being spread by aphids. In all likelihood, the disease had been present at low levels in Egypt for some time but had not previously shown itself in quite such devastating magnitude. FBNYV is considered the most economically important disease-inducing agent to the faba bean crop, especially in Middle Egypt. It is also economically damaging in the Jordan Valley and in coastal areas of Syria and Turkey where winters are sufficiently mild to sustain the aphid population.

        This virus disease can reach epidemic proportion in Egypt, causing considerable losses, as happened in 1992 and 1999 when some faba bean growers were faced with complete crop failure. As a result, many Egyptian growers were reluctant to plant nutritionally-vital faba bean crops in subsequent years.
        Because of the seriousness of the disease, and to reduce the losses caused by it, intensive efforts were made by the Agriculture Research Center in Egypt, in collaboration with ICARDA through its Nile Valley and Red Sea Regional Program based in Cairo, with financial support from the EU, to develop measures both acceptable to farmers and without adverse effects on the environment.
        The virus causing the disease is introduced to the crop through plant-sucking aphids such as the pea aphid (Acyrthosiphon pisum) and the cowpea aphid (Aphis craccivora). The aphids acquire the virus when feeding on virus-infected summer legumes such as cowpea (Vigna unguiculata) or French bean (Phaseolus vulgaris) or a large number of virus-infected leguminous weeds, which are part of the natural habitat along the irrigation canals and between fields in Egyptian agricultural land.
        Middle Egypt is characterized by a mild winter where temperatures rarely fall below 5°C. Accordingly, aphids can actively move from such hosts and fly into the faba bean fields in October-December. They introduce the virus into faba bean plants when they start feeding on them. The virus is contained in the saliva of the aphid and transmitted while feeding takes place.

and the use of two systemic aphicide sprays in December and January. The success of this integrated virus disease management scheme in minimizing disease losses on experimental farms was such that the approach is now being taken to farmers' fields.
        Parallel to these investigations, the collection of faba bean germplasm in the ICARDA gene bank was examined in 1998/1999 to identify faba bean genotypes resistant to FBNYV infection. Preliminary results showed that a few genotypes which originated from Ethiopia, Greece, Libya, Morocco, Russia and Turkey were highly resistant. It is still too early to say definitively that there will be fully-resistant varieties. However, if such resistance is confirmed after evaluating these genotypes under Egyptian environmental conditions, then breeders in Egypt will have useful sources of resistance for use in developing faba bean cultivars, both adapted to local conditions and resistant to FBNYV infection.
        The availability of an adapted resistant variety might then permit the establishment of an integrated management option without the use of insecticides, or at least it could reduce the number of sprays. This would minimize costs to growers and risk to the environment.

Dr Khaled M. Makkouk is Acting Leader of the Germplasm Program at ICARDA. Drs Latif Rizkallah, Samia Mahmoud and Mamdouh Omar are all Senior Scientists at the Agricultural Research Center, Giza, Egypt.