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POSTERS: Chemical control

Efficacy of fungicides and biotic agents for the control of basil downy mildew in Illinois
Eric Johnson - USDA ARS. Mohammad Babadoost- University of Illinois - Crop Sciences Dept, Guirong Zhang- USDA ARS, David Schisler- USDA ARS MWA NCAUR, Alan De Young- Van Drunen Farms

Basil downy mildew (Peronospora belbahrii) is a pathogen of sweet basil (Ocimum basilicum). While the disease is well controlled by fungicides, it is imperative to develop a management plan to keep the pathogen from developing fungicide resistance. Several fungicides were sprayed on basil weekly in varying combinations, application rates, and sequences over the course of one field season, and the treatment effects were evaluated on three different dates. The treatments included mixtures and different rotations of azoxystrobin, potassium phosphite, mandipropamid, cyazofamid, oxathiapiprolin, experimental compound A18269SE, dimethomorph, zoxamide + mancozeb, fluazinam, fluopicolide, mefenoxam + copper hydroxide, fenamidone, mancozeb, and ametoctradin + dimethomorph. All fungicide treatments significantly lowered the area under the disease progress curve (AUDPC) values compared to the untreated control. Cyazofamid and mandipropamid were both utilized in three different fungicide regimes that resulted in the lowest AUDPC values. Two novel biological control organisms (Bacillus amyloliquefaciens AS 43.3 and Papiliotrema flavescens OH 182.9 3C) were also tested for efficacy on basil downy mildew in greenhouse experiments. Azoxystrobin, the positive control, was effective against the pathogen, but the biological control organisms did not reduce disease severity. More experiments are needed to identify effective biological control organisms for basil downy mildew.