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Accelerated soil degradation with repeated application was suggested to be responsible for the lack of efficacy of commercial fungicides to control lettuce drop caused by Sclerotinia minor in the Salinas Valley in California. In 2000, a study was initiated in a field artificially infested with S. minor to evaluate the efficacy and degradation potential of four selected fungicides (i.e., Rovral, Botran, Switch, and Endura). Crisphead lettuce was direct-seeded twice a year (spring and fall season) from 2000 to 2002. Fungicides were applied at recommended label rates twice during each season. Disease incidence was evaluated in fungicide treatments and nontreated control plots weekly starting immediately after thinning until harvest, and areas under the disease progress curves (AUDPC) were compared between treatments from 2000 to 2002. Soil samples (0–15 cm) were collected at regular intervals during the spring and fall 2002 lettuce seasons, and analyzed for residual fungicide concentration. Disease progress and final disease incidence were significantly affected by the fungicide treatment, season, year and interactions among these factors (p

Downy mildew, caused by Sclerospora graminicola, is a major pathogen of pearl millet (Pennisetum glaucum) in Asia and Africa. So development of resistant cultivars has been a major goal of national and international breeding programs. Stability of resistance in pearl millet lines developed at ICRISAT was studied through a collaborative International Pearl Millet Downy Mildew Virulence Nursery (IPMDMVN). The reactions to downy mildew of 11 pearl millet lines at 17 locations in India, Burkina Faso, Mali, Niger, and Nigeria from 1995 to 1999 were recorded. Disease incidence varied significantly among lines, locations, and years. The tested pearl millet lines exhibited significant differential resistance. Resistance in lines IP 18292, IP 18293, 700651 and P 310-17 was most stable regardless of the location or season. Analysis of the variation in resistance also suggested that the resistance in IP 18292 and IP 18293 was variable and depended on the locations and years, while the resistance in 700651 and P 310-17 was highly stable across locations and over years. The latter two lines could prove to be the most valuable sources of downy mildew resistance. The results also revealed significant differences in S. graminicola populations at different locations, with the highest disease at Bagauda (Nigeria) and Durgapura (India) and lowest from Coimbatore and Aurangabad (India). Based on the reaction of the 11 pearl millet lines, the 17 S. graminicola populations were grouped into six putative pathotypes (undefined populations closer to races).