RESUMEN
OBJECTIVE: To study the pathogen of opium poppy downy mildew and its biological characteristic for further research on the disease. METHOD: Development of the disease was observed systematically in the field. Germination rate of sporangium in different temperature, pH and nutrition was examined with suspending-drop method. Slide-germination method was used to observe its germination in different humidity maintained by different concentration of H2SO4. RESULT AND CONCLUSION: The disease manifests itself in two forms: severely infected plants (systematic infection) and leaf spots (nonsystematic infection). Sporangia of the pathogen are oval or globular, thin walled, smooth, hyaline, with 7.74-16.34 microns diameter in base 1 and 8.34-15.05 microns in base 2.0 ospores are light yellow with 33.87-70.54 microns x 19.34-62.64 microns in base 1 and 36.85-49.68 microns x 42.08-55.76 microns in base 2. Conidiophores are stout, erect, whose branching times and length are different between those in base 1 and those in base 2. Sporangia sprot directly in two hours. Film of water is necessary for sporangium to sprot. The optimum temperature range of sporangium sprot is 12-21 degrees C, the best being 16 degrees C, the pH range is 4.53-9.18 the best optimum at pH 7.38, and the extract of leaf of 1:5 is good for its germination.
Asunto(s)
Oomicetos/crecimiento & desarrollo , Papaver/microbiología , Humedad , Concentración de Iones de Hidrógeno , Oomicetos/ultraestructura , Enfermedades de las Plantas/microbiología , Esporas Fúngicas/crecimiento & desarrollo , Esporas Fúngicas/ultraestructura , TemperaturaRESUMEN
OBJECTIVE: To screen effectual fungicides for field control because of the seriousness of opium poppy mildew and importance of chemical control on plant diseases. METHOD: Seven fungicides were screened in Lab experiment and field test during 1996-1997. RESULT AND CONCLUSION: All of them and their different dosages were effective to control conidia of Peronospora arborescens. Among them, 72.2% propamocarb of 1203 and 902.5 ppm were the most effective both in Lab experiment and field test with efficacy 79.91% and 79.33% respectively in field test, and the efficacy of other fungicides was over 50%. Seven fungicides tested can be used to control nonsystematic symptom of opium poppy mildew.