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Downy mildew of broccoli, caused by the fungus peronowora parasitica, usually can be found on a yearly basis in broccoli fields in Arizona During the 1988-89 season, four different fungicides were evaluated in the field for disease control. All four materials significantly reduced the number of downy mildew lesions on treated broccoli leaves. Although significant disease control was achieved the average head weight was not significantly different when treated plants were compared with untreated plants. Light to moderate levels of downy mildew or late development of disease, as found in this trial, apparently do not require application of fungicides to prevent yield loss. Ridomil/Bravo and Bravo currently are registered for disease control, while SDS-59891 and Aliette are not registered for use on this crop.

Downy mildew of broccoli is caused by the plant pathogenic fungus Peronospora parasitica. Cool damp weather with high humidity is highly favorable for sporulation, dissemination of spores, and infection by this pathogen. The severity of disease is affected by the duration of weather conditions favorable for disease development. Potential new fungicides were evaluated for disease management in a field trial conducted in 1996. Disease pressure was moderate and all tested fungicides except Ridomil MZ 72 and one Ciba G + Mancozeb treatment significantly reduced the number of downy mildew lesions on leaves compared to plants not treated with a fungicide. The level of disease reduction provided by all chemical treatments was equivalent to that given by Aliette and Bravo, two fungicides currently available for control of downy mildew on broccoli.

Downy mildew of broccoli, cabbage, and cauliflower is caused by the plant pathogenic fungus Peronospora parasitica. Cool damp weather with high humidity is highly favorable for sporulation, dissemination of spores, and infection by this pathogen. The severity of disease is affected by the duration of these weather conditions favorable for disease development. Potential new fungicides were evaluated for disease control in a field trial conducted in the winter of 1992-93. For broccoli, no significant differences in disease severity were detected among treatments. On the other hand, Microthiol and Microthiol + Maneb significantly reduced the number of downy mildew lesions on cabbage and cauliflower compared to nontreated plants. Maneb alone provided significant disease control on cabbage, but not on cauliflower.