El mildiu de las crucíferas en el término de Villa del Prado (Madrid): apuntes epidemiológicos

SiNOBAS ALONSO, J. y DIAZ ALONSO, M., 1995: The Mildew of the crucifers in the district of Villa del Prado (Madrid): Epidemiological notes. Bol. San. Veg. Plagas, 21(4): 497-506. The mildew efect of the crucifers, causal agent Peronospora parasitica (Pers.) has been studied in the district of Villa del Prado (Madrid) as well as the influence of the enviromental factors in the development of the epidemic. The evolutionary study of the disease through the years 1991 and 1992 in the kale, seed nursery and weed cropping allowed us to observe the first symptoms of the disease at the beginning of October, 1991 reaching the higest incidence in December of the same year. The plantules obtained in seed nurseries in winter were inocule-bearing, which was not observed in spring-summer plants. The seed nursery plantules obtained in summer in the open air do not seem to be primary inocule-bearing for the summerwinter croppings. Among the surveyed weeds Peronospora parasitica was identified as one of the genus Sisymbrium. The disease intensity (DI) shows the positive correlation with the relative humidity (RH) on one hand, and the negative correlation with mean temperature and with the number of hours of daily insolation on the other. A low number of hours of insolation for several consecutive days in combination with cool temperatures seems to be determinant factor in the development of the disease. The correct moment for the application of preventive treatments could take place when these circumstances occur.