02281naa a2200169 a 450000100080000000500110000800800410001910000190006024500930007926000090017252017890018165000160197065000210198665000270200770000190203477300580205311326022022-10-14       2022    bl uuuu     u00u1 u    #d1 aARAÚJO, E. R.  aFungicide efficacy to control onion downy mildew in Brazil, 2021.h[electronic resource]  c2022  aOnion downy mildew, caused by Peronospora destructor, is the main foliar disease in Santa Catarina (Brazil's largest production state). This trial aimed to evaluate the effect of fungicide sprays on the area under the disease progress curve - AUDPC and on the commercial yield of onion in experimental plots under field conditions. Onion seedlings were grown on a soil bed and approximately 60 days after sowing, they were transplanted (July 19, 2021) to the experimental area. The experimental plots consisted of 150 plants (six rows with 25 plants) arranged in a spacing of 0.10 m (between plants) and 0.35 m (between rows), simulating a plant density of approximately 300,000 plants per hectare. The treatments started 25 days after transplanting. Eleven weekly sprays were performed, with a volume corresponding to 500 L/ha. The severity was assessed fortnightly using a rating description scale, which assigns scores to the entire plot (score 1 = 0% severity to score 9 = 100% severity). The values from scale scores of the experimental plots were used to calculate AUDPC. The harvest was carried out 123 days after transplanting. Commercial yield (onion bulbs with diameter ≥ 35 mm) was calculated from the central rows of each plot, discarding single border rows (Table 1). The experiment was randomised in blocks designed with four replications. The data were analysed using ANOVA and, in case of significance of the treatments, means were grouped with Scott-Knott cluster. The fungicide treatments did not differ statistically from each other in terms of AUDPC and yield, however, all were superior to the control treatment. The fungicide sprays increased yield from 17.54% to 26.67% compared to the control. No visual phytotoxicity symptoms were observed in the assay.  aAllium cepa  achemical control  aPeronospora destructor1 aRESENDE, R. S.  tPlant Disease Management Reports, St. Paul, MN, 2022.