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 2002, ICARDA identified and released new sources of resistance to lentil vascular wilt, and continued to refine the use of promising, insect-killing fungi isolates as a means of controlling Sunn pest (an insect which attacks barley and wheat crops). A new screening technique was also developed to identify wheat varieties resistant to Sunn pest damage: several promising lines have already been identified. Yellow rust populations in the CAC region were characterized, identifying resistance genes with the potential to be effective throughout the region. Finally, research continued into the integrated management of chickpea chlorotic dwarf virus, barley leaf blotch diseases, Hessian fly in wheat, and ascochyta blight in chickpea

Integrated pest management in cereal and food legume crops

In CWANA, cereal and food legume production is severely affected by a number of diseases and insect pests. The most important of these are rusts; leaf blotch diseases (septoria, tan spot, scald, ascochyta blight, chocolate spot); viral diseases (BYDV, BNV); seed-borne diseases (smuts, barley stripe); root rot diseases (fusarium wilts, fusarium head scab); and insect pests (aphids, Hessian fly, Sunn pest, leaf miner, wheat stem sawfly). Research has focused on host-plant resistance, and several sources of resistance have been identified and utilized in the wheat, barley, lentil, faba bean, and chickpea breeding programs at ICARDA and in the collaborative NARS programs. The search for new sources of resistance is an important activity undertaken by the IPM project. Resistant sources, from the ICARDA breeding nurseries and genebank, are provided to breeding projects annually, by the plant health group. Monitoring of pest biotypes/pathotypes and changes in virulence are a major concern, and ICARDA conducts annual surveys in collaboration with its NARS partners to address this.
     The most effective way to maintain a low threshold of major pests and reduce crop losses is to implement an IPM approach. Therefore, biological control agents are being developed, and have shown promise in the control of Sunn pest (Eurygaster integriceps). IPM options (including selected cultural practices, host resistance, provision of high-quality seed, and limited use of pesticides) have also been successfully used by farmers to control Hessian fly (in Morocco) and chickpea ascochyta blight (in Syria). The following summaries highlight some examples of pest management, and show that pre-emptive control and avoidance of epidemics and subsequent crop losses could be achieved through well-planned and coordinated research, in close collaboration with NARS scientists and farmers.

Innovations in Sunn pest control

Sunn pest (Eurygaster integriceps) is a serious pest of wheat and barley in the CWANA region, and contributes to both yield losses and processing problems. ICARDA and its partners are working on new Sunn pest control methods, and in 2002 conducted a number of relevant laboratory and field-based studies.

Field testing of promising insect-killing fungi

Scientists are now testing a promising new biological control method, involving natural enemies of Sunn pest-insect-killing fungi. Laboratory bio-assays of fungi collected from Sunn pest populations across CWANA led to certain isolates being selected for testing in the field. Trials were then conducted to determine the effectiveness of introducing fungi to Sunn pest overwintering sites. Scientists found that significantly greater mortality resulted in plots treated with Beauveria bassiana and a Metarhizium anisopliae than in the controls. A high

Using standardized bioassay methods for Sunn pest, both in litter and on plants, researchers tested several fungal strains isolated in 2001 at Iranian overwintering sites. In most cases, Sunn pest mortality was greater when the fungal isolates were applied to litter than directly to plants (Fig. 8). Although the Paecilomyces farinosus isolates were not particularly effective, three of the Iranian B. bassiana isolates tested showed great potential for Sunn pest control. Additional isolates are available for testing in the coming year. This work was carried out in collaboration with the University of Vermont, and was funded by DFID and USAID.

Detailed molecular characterization studies were conducted on promising isolates of Beauveria bassiana to investigate their genetic diversity. These were carried out as part of a DFID-funded IPM project on Sunn pest in West Asia, in collaboration with CABI Bioscience and the University of Vermont. DNA was extracted from a total of 112 isolates (106 of Beauveria bassiana, 5 of other Beauveria species and 1 of Beauveria brongniartii) obtained from surveys of Sunn pest and related insects. Four techniques were used: ISSR-PCR (Inter-Simple Sequence Repeat PCR), AFLP, restriction analysis of the ITS (Internal Transcribed Spacer) region, and ITS sequencing. The latter two methods did not detect genetic variation among the B. bassiana isolates. However, results from both the ISSR-PCR and the AFLP analyses clearly indicated genetic diversity among the isolates, and revealed some intraspecific groupings in the various geographical origins (Fig. 9).

Status of yellow rust in Central Asia and the Caucasus region

Yellow rust (caused by Puccinia striiformis f. sp. tritici) is an important disease of wheat in most wheat-growing regions, including the Caucasus, West Asia, Central Asia, the Nile Valley and the Horn of Africa. In East Africa, the Middle East, China, the Caucasus, and Central and West Asia, yellow rust epidemics have caused severe wheat crop losses over the past decade. During the 2001/02 season, at least 30-40% yield losses were recorded in major wheat-producing areas of Azerbaijan, Kyrgyzstan, and South Kazakstan. In Uzbekistan, however, over 60% of the country's wheat-producing area has been protected with fungicides.
      Enhanced development and spread of yellow rust in Central Asia and the Caucasus can be attributed to three major factors: (1) environmental effects, (2) the nature of the cultivars employed, and (3) pathogenic evolution.
     An example of the first factor is the yellow rust epidemic observed in Central Asia in 2002, which was exacerbated by extended periods of cool wet spring weather in regions that normally experience a rapid temperature increase during this period. Under such conditions of severe inoculum pressure, cultivar response to Puccinia striiformis f. sp. tritici (or Pst) was unexpectedly variable. Other environmental effects, which may also have an impact, include the development of irrigation facilities, and the expansion of wheat cultivation into fertile regions (such as the Fergana Valley in Tajikistan).
     A limited number of cultivars (such as 'Yuna,' 'Steklovidnaya,' 'Spartanka,' 'Sanzar4,' 'Sanzar8,' 'Skifyanka,' and 'Mirbachir') are grown over large areas of the CAC region. These cultivars are highly susceptible to yellow rust, and therefore contribute to the rapid increase of the inoculum. The resultant high disease pressure also causes moderately resistant varieties ('Zhetysu,' and 'Polovchanka') to succumb.
     The final factor underlying change in cultivar disease response is pathogenic evolution. It is possible that, in the CAC region, the evolution of Pst has followed a series of step-wise mutation events, including occasional reversions to virulence (this appears to have occurred in Tajikistan). It is also possible that genetic recombination has occurred in the Pst pathogen, in areas where the rust spores of different pathotypes (races) have been blown in by the wind from different regions (this seems to have occurred in Kyrgyzstan and Azerbaijan).
     The yellow rust population in the CAC region consists of a number of pathotypes that differ in their pathogenicity toward the host plant. Some (such as 2E0 and 6E0) attack only two resistance genes in the host plant, others (such as 198E150, 230E150) can attack 11 identified genes in the host plants. In collaborative research conducted by ICARDA and NARS in the CAC region, yellow rust populations were characterized using two methods: (1) the Central Western Asia Yellow Rust Trap Nursery (CWAYRTN), planted at yellow rust "hot spots" in Azerbaijan, Uzbekistan, Kyrgyzstan, Tajikistan and Kazakstan, and (2) artificial inoculation at experimental stations in Syria, Lebanon and Turkey. By 2003 and 2004, respectively, the Absheron station in Azerbaijan and the selection station in Bishkek, Kyrgyzstan, will have the capacity to conduct artificial inoculation (allowing proper selection to be made under conditions of disease pressure).
     Analysis of this collaborative research showed that most single resistance genes were defeated in at least one testing site in the Central Asia region, and that gene combinations offered better resistance. Of the 30 resistance genes available, only the following seven remained effective across the whole CAC region:

• YrSP and YrCV—available in facultative and spring bread wheat;
• Yr10, Yr3V and Yr3N—available in winter wheat;
• Yr5 and Yr15—available in wild relatives of wheat (Triticum spp.).
  

     The level of resistance that Yr18 alone provides in adult plants may not be sufficient in environments highly conducive to yellow rust development. Even so, it may provide useful protection in terms of yield. Leaf tip necrosis, possibly a linked characteristic, may assist in the selection of plants possessing this gene. Combining Yr18 with other genes (such as Yr29 and the components of resistance found in a wheat variety such as 'Cappelle Deprez') could produce adequate and perhaps durable resistance in most environments.
     The germplasm provided by the CIMMYT/ ICARDA wheat program contains a high degree of genetic diversity in terms of race-specific genes that are currently effective in most CWANA countries. Though the diversity of yellow rust's population creates problems, more information is slowly emerging concerning both examples of durable resistance to yellow rust in wheat and the genetic control of such resistance. Evidence suggests that adequate levels of resistance could be obtained using a few additive genes, each having a small to moderate effect. However, improvement is still needed in the application of programs intended to achieve durable resistance to yellow rust in wheat. In the CAC region, surveys of pathogen populations and the genetic characterization of resistance continue to provide information valuable in the design of breeding strategies.

Integrated management of chickpea stunt in northern Sudan

Chickpea stunt, caused by chickpea chlorotic dwarf virus (CpCDV), is an important disease of chickpea in central and northern Sudan. In collaboration with the Agriculture Research Corporation, ICARDA conducted experiments at the Hudeiba Research Station in northern Sudan during the 1999/00, 2000/01 and 2001/02 growing seasons. This research evaluated the influence of cultivar type ('Shendi' and 'ICCV-2'), sowing date (late October, early November and late November) and irrigation interval on the natural spread of CpCDV in chickpea fields.
     Virus incidence was lower in cultivar 'Shendi' than in 'ICCV-2', regardless of the planting date used during the 1999/00 and 2001/02 growing seasons. Delayed sowing reduced CpCDV incidence in both cultivars during all three growing seasons (Table 16). In fact, in one season, virus incidence was 93% in a crop of 'ICCV-2' sown in late October, but only 29% in a crop sown just 28 days later. Short irrigation intervals also reduced virus incidence during the 1999/00 and 2001/02 growing seasons (Table 17). Therefore, the combined effect of partial resistance, delayed planting and irrigation at short intervals proved useful in CpCDV management in chickpea fields in northern Sudan.

RImpact of farmers' practices on barley disease control in Tunisia

Barley is cultivated mainly in the semi-arid regions of Tunisia. In these regions production is relatively low, and barley leaf blotch diseases cause significant yield losses. Therefore, ICARDA, in collaboration with Tunisian researchers, conducted a large-scale investigation, covering 1576 farmers' fields, to determine the association between disease severity, grain yield and cultural practices (which included the use of fungicides, fertilizer, and local and certified seed).
     Scientists found that the main barley varieties grown in the region were 'Rihane' (76%), 'Manel' (14%) and 'Tej' (5%): local landraces made up only 5% of the total. The predominant blotch diseases were scald (Rhyncosporium secalis) and net blotch (Pyrenopora teres f. teres), covering 87% of the area. Powdery mildew and leaf rust occurred at a lower frequency (28%). Farmers mainly used the fungicides Opus (Epoxyconazole), Tilt (Propiconazole) and Sportak (Prochloraz), and applied nitrogen (ammonium nitrate, 33.5%) and phosphate (Super 45-P2O5, 45%) fertilizers at rates that ranged from 15 kg to 200 kg/ha and 80 kg to 150 kg/ha, respectively.
     Fungicide treatments were applied more on small farms than on larger farms: 58% of farms less than 30 ha in size were treated, yet this figure was less than 15% for farms between 30 ha and 120 ha in size. The existence of a government assistance program, aiming to enhance cereal production by small farmers, explains this use of fungicides on small farms.

Funded by the CGIAR's Systemwide Initiative on IPM, the second year of the IPM Farmer Participatory Training and Research program was completed during the 2001/02 growing season. Each of the program's six sites (located in the Sidi El Aidi, Ain N'Zagh and Jemaa Shaim regions) tested the following IPM options:

• Two bread wheat varieties ('Aguilal' and 'Arrihane') resistant to Hessian fly, against a susceptible bread wheat ('Marchouch') using an early planting date.
• One resistant bread wheat variety (either 'Aguilal' or 'Arrihane'), against a susceptible one ('Marchouch') using a late planting date.
• Winter chickpea (early planting) vs. spring chickpea (late planting)-'Rizki' vs. a local landrace.

Winter (left) vs. spring-sown chickpea in Morocco.

Click on it