Down Mildew of Broccoli - Effect of Fungicides on Disease Control and Crop Yield

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.