ICARDA Annual Report 2001

An integrated pest management (IPM) approach is one in which farmers use the most efficient combination of options to protect a crop from insects and diseases. Employing a range of options, such as host plant resistance, biological control, suitable agronomic practices, and habitat management, allows chemical control to be reduced and strictly targeted, benefiting human health and the environment. In 2001, ICARDA scientists continued to gather knowledge and information on current pest and disease threats throughout the CWANA region. Further studies on natural enemies of sunn pest, an insect that attacks wheat and barley crops, revealed interesting possibilities for biological control. Pilot sites were established in Egypt and Morocco to identify and validate 'best bet' IPM options for these locations. An integrated disease management package was developed to protect chickpea from fungal attack by ascochyta blight.

Cereal growing areas in Central Asia and the Caucasus (CAC) are particularly susceptible to pest and disease attack as they are characterized by large-scale monoculture of a limited number of wheat and barley varieties. The prevailing climate is also conducive to the spread of disease. The most common diseases observed in 2001 in Azerbaijan, Kazakstan, Kyrgyzstan and Uzbekistan were yellow rust, tan spot, powdery mildew, scab, leaf rust, root rot, Septoria tritici, Septoria nodorum, and common bunt on wheat; and leaf rust, scald, net blotch, barley stripe, smuts, and powdery mildew on barley. The frequency of occurrence of the most prevalent diseases showed a common trend across the region (Fig. 9).

Yellow rust (Puccinia striiformis f.sp. tritici) is still the most widely spread disease of bread wheat in Central Asia. New races are spreading rapidly, and there is a danger that current sources of resistance will become ineffective. Most commercially grown wheat varieties are already highly susceptible.

Tan spot (Pyrenophora tritici repentis) is another rapidly evolving disease of both durum and bread wheat. The disease was found in virtually all fields that are cropped in the traditional system, consisting of a succession of spring and winter wheat in rotation with fallow. Scald and powdery mildew are the most apparent diseases in case of barley, but seed-borne diseases (smuts and barley stripe) are also prevalent throughout Azerbaijan, Kazakstan, Kyrgyzstan, and Uzbekistan.

A preliminary survey to identify virus diseases affecting wheat in Uzbekistan was conducted during 2001. The survey covered 12 wheat fields in two cereal growing regions (Tashkent-Angren and Tashkent-Samarkand). A total of 250 wheat samples with virus symptoms were collected and tested for the presence of nine different viruses using tissue blot immunoassay. Results indicated that barley yellow dwarf virus was the most common disease, while barley yellow striate mosaic virus and cereal yellow dwarf virus were reported for the first time.

Insect surveys were conducted in Uzbekistan, Kyrgyzstan, and Kazakstan. Samples from 19 wheat and barley fields in Uzbekistan revealed that sunn pest (Eurygaster integriceps), cereal leaf beetle, thrips, and aphids were the major pests. Interestingly, the sunn pest population was lower than in 1999, but the level of damage was expected to increase before harvest due to feeding by the remaining nymphs and the new generation adults. Cereal leaf beetle damage was high (40%) in most areas surveyed except in the east, while infestation by thrips and aphids was highest in the Tashkent area. In Kyrgyzstan, 25 wheat and barley fields were surveyed. Here, the major insect pests were sunn pest, cereal leaf beetle, thrips, shoot fly, and Russian wheat aphid. Major insect pests in Kazakstan (from a survey of 32 wheat and barley fields) were sunn pest, thrips, aphids, cereal leaf beetle, frit fly, and Hessian fly. Here sunn pest damage was less severe than in the other two countries. Cereal leaf beetle damage was high in Syram region but low in other regions. Heavy thrips infestation was observed on spring wheat and barley, the latter being also severely affected by frit fly in some areas. In Taras region, about 80% of wheat spikes had aphids feeding on them. Hessian fly and green bug damage were observed on wheat in Almaty region, but in general, Hessian fly damage was more pronounced in rainfed fields.

In Iran, a survey was conducted to identify virus diseases affecting chickpea and lentil. A total of 8739 random and 1443 symptomatic samples were collected and tested for the presence of 10 legume viruses by the tissue blot immunoassay procedure. In chickpea fields, chickpea chlorotic dwarf virus was the most common, followed by bean leaf roll virus, faba bean necrotic yellows virus, and beet western yellows virus. In lentil fields, pea enation mosaic virus and bean leaf roll virus were the most common.

A survey to identify virus diseases affecting faba bean, chickpea, barley, bread wheat, and durum wheat was conducted in Tunisia as a continuation of the 2000 survey. The main objective was to determine which viruses affect legume and cereal crops in the different production areas. In faba bean fields, faba bean necrotic yellows virus was the most common, followed by luteoviruses and broad bean mottle virus. In contrast, only luteoviruses were detected in chickpea fields. In cereal fields, barley yellow dwarf virus was the most common followed by barley stripe