02614naa a2200169 a 450000100080000000500110000800800410001910000190006024501070007926000090018652020990019565000160229465000230231065000270233370000190236077300650237911340172023-12-08       2023    bl uuuu     u00u1 u    #d1 aARAÚJO, E. R.  aEfficacy of fungicide treatments to control onion downy mildew in Brazil, 2022.h[electronic resource]  c2023  aThe State of Santa Catarina is the largest Brazilian producer of onions, with an annual production of over 400 thousand tons. Onion downy mildew (Peronospora destructor) is the main onion disease in the state. The management of the disease is carried out through frequent fungicides sprays (one to two sprays per week). 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 field plots. Onion seedlings were grown on a soil bed and approximately 60 days after sowing, they were transplanted (12 Jul) 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 30 days after transplanting. Ten weekly sprays were performed, with a volume corresponding to 500 L/ha. The severity was assessed every two weeks 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 121 days after transplanting. Commercial yield (onion bulbs with diameter ≥ 35 mm) was calculated from the central rows of each plot, discarding single border rows. 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 the Scott-Knott clustering algorithm. The disease occurred naturally, allowing for proper evaluation of the trial. Antracol® + two applications of Zorvec Encantia® resulted in the highest yield, with an increase of 47.5% in relation to the control treatment. The treatments Zorvec Encantia®, Ridomil Gold® MZ, and Completto® differed from the control, with an increase of 33.6%, 27.0 % and 23.5%, respectively. No visual phytotoxicity symptoms were observed in the trial.  aAllium cepa  adisease management  aPeronospora destructor1 aRESENDE, R. S.  tPlant Disease Management Reports, St. Paul, MNgv. 17, 2023.