Spray solution deposition and Asian rust control in soybean cultivars¹

Deposição de calda e controle da ferrugem asiática em cultivares de soja

HIGHLIGHTS:

Medium-sized droplets provide better coverage in the lower layers of the soybean canopy under limiting climate conditions.

Nozzles 11002BD and AIXR11005 provide better spray solution deposition in soybean cultivars with lower leaf area indexes.

Leaf area can be used as a parameter in selecting the appropriate droplet size for spraying.

ABSTRACT

The control of Asian soybean rust depends on fungicide efficacy and the application technology; however, the leaf architecture of soybean cultivars may also interfere in disease control. This study aimed to evaluate Asian rust control and fungicide deposition using spray nozzles in three soybean cultivars. A randomized block design was used, with treatments arranged in a split-plot scheme; the plots were three soybean cultivars (SYN 1561 IPRO, M6410 IPRO, and M6210 IPRO) and the subplots three spray nozzles (11002 BD, AIXR 110015 and TTJ60 11002), in addition to a control with no fungicide application, and four replicates. The volume median diameter, droplet coverage, leaf area index, area under the disease progress curve, 1,000-grain weight and crop yield were evaluated. The 11002BD and AIXR11005 nozzles provided better spray deposition in cultivars with lower leaf area indexes at the R1 phenological stage. Nozzles 11002BD, AIXR110015 and TTJ60 ensured better management of Asian rust than that of the control treatment, regardless of leaf area index. Cultivar SYN1561 obtained the largest grain yield and highest leaf area index in the season with the highest rainfall, regardless of the spray nozzle used.

Key words:
Glycine max; Phakopsora pachyrhizi; application technology; droplet density; fungicides