Management of Powdery Mildew in Nurseries in Hawaii
: In Hawaii, floriculture crops are plagued by fungal diseases caused by powdery mildew. White patches of mildew and scars created by its growth make ornamentals unmarketable. Persistent mildew problems occur on zinnia, Gerber daisies, poinsettia, begonia, African violets and many other plants. Growers rely on fungicides such as thiophante methyl (Cleary 3336, Domain, Systec) and chlorothalonil (Bravo) to control mildew. The purpose of this project is to show that lower risk pesticides will control mildew in ornamental crops. The crops to be tested are zinnia and Gerbera and the low risk pesticides chosen for testing are sulfur, potassium bicarbonate (Kaligreen from Monterey Chemical Company) and Azoxystrobin (Heritage from Zeneca).
Project goals and objectives
Test eight treatments (including control) to determine if lower risk pesticides will control mildew in ornamental crops.
Hertitage and Kaligreen were effective controls for powdery mildew on Gerbera. Kaligreen is relatively economical compared with Heritage and Systhane and each represents different chemical groups, making rotation feasible. These products give growers new options to control this common market limiting disease. Kaligreen has to be re-applied every two weeks for disease control.
Spray applications of strobilurin compounds, potassium bicarbonate and Fortress or quinoxyfen controlled powdery mildew on gerbera.