Occurrence and epidemiology of pearl millet downy mildew, Sclerospora graminicola, in southwest Niger

Abstract

The constraints upon pearl millet ( Pennisetum glaucum (L.) R. Br.) cultivation were investigated in four regions in southwest Niger. Drought and low soil fertility constitute the principal problems according to farmers. Pearl millet downy mildew ( Sclerospora graminicola (Sacc.) Schroet.) is one of the possible biotic constraints. Its occurrence and epidemiology were studied in two regions in southwest Niger with different mean annual rainfalls. Disease incidence ranged from 7.6% to 42.0% in the area with highest rainfall and from 0% to 16.4% in the drier region. Disease severity ranged from 4.3% to 24.8% and from 0% to 8.5%, respectively, in the two regions, which gave a good indication of estimated crop loss. Oospore density in the soil was highly correlated with disease incidence at 90 days after sowing ( r = 0.83, 18df) indicating the important role of oospores in disease epidemiology. Soil organic C content, pH(H2O) and loam fraction showed significant correlations with disease incidence ( r = 0.70, 0.47 and 0.46 respectively, 18df), but fractions of sand and clay were not significantly correlated with disease incidence ( r = 0.39 and 0.13 respectively, 18df).