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Poster: Biology & Disease Mgmt: Chemical Control


Interaction among leaf area index, spray volumes and fungicide doses in Asian soybean rust control
A. CHECHI (1), W. Boller (1), C. Forcelini (1), R. Roehrig (1), E. Zuchelli (1) (1) UPF, Brazil

Soybean cultivars vary in their leaf area index (LAI), which influences the distribution of the drops generated by the spray fungicides in plant canopy. The objective of this study was to investigate the interaction among the LAI, spray volumes and fungicide doses in controlling Asian soybean rust. The tests were conducted at UPF experimental field, greenhouse and growth chamber during 2014 to 2016. The dose was varied (75%,100% and 125% of the commercial dose) and the spray volume (100,150 and 200 L/ha) at application of fungicides on soybean plants with different LAIs. An assay was also conducted with the use of simulated rainfall at different times after the fungicide application. There were three cultivars in the experimental field: BMX Ponta (high LAI); BMX Vanguarda (medium), NS 5445 (low), and only the last one in the other trial. The applications were in V7 stages (trifloxystrobin+prothioconazole), R1 and R1+20 days (azoxystrobin+benzovindiflupir) for field trials and only in V8 stage for testing in the greenhouse. The severity of the rust, the number of spores/cm2, the LAI and the grain yield were quantified and analyzed by Anova and Skott-Knott test (0.05). The results showed that the spray volume and the fungicide dose should be appropriate according to the cultivar LAI. The closer the application when rain occurs, lower the control achieved by applying the fungicide. The cultivar LAI, spray volume and the fungicide dose influenced the disease control.