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Assessing herbicide symptoms by using a logarithmic field sprayer

Cunha, Beatriz Ribeiro da, Andreasen, Christian, Rasmussen, Jesper, Nielsen, Jon, Ritz, Christian, Streibig, Jens Carl
Pest management science 2019 v.75 no.4 pp. 1166-1171
Sinapis alba subsp. alba, canola, cropping systems, crops, diflufenican, dose response, field experimentation, regression analysis, sprayers
BACKGROUND: In field experiments, assessment of herbicide selectivity and efficacy rarely takes advantage of dose–response regressions. The objective is to demonstrate that logarithmic sprayers, which automatically make a logarithmic dilution of a herbicide rate, can extract biologically relevant parameters describing the efficacy of herbicides in crops, and compare localities and time of assessment. RESULTS: In a conventional and an organic field, canola, white mustard, and no crop plots were sprayed with diflufenican and beflubutamid. A mixed effect log‐logistic dose–response regression, with autoregressive correlation structure, estimated ED₅₀ and ED₉₀ for visual and Excess Green Index symptoms at various days after treatment (DAT). For visual assessment, ED₅₀ differed within no crop between locations for beflubutamid at 12 DAT and 26 DAT. For diflufenican, the ED₅₀ was different within crops at the two fields at 12 DAT, but not at 26 DAT. The Excess Green Indices at ED₅₀ were not different among herbicides, locations, and corps; ED₉₀ differed for white mustard and canola for beflubutamid but not for diflufenican. CONCLUSION: Suitable nonlinear regression models are now available for fitting dose–response data from a logarithmic sprayer in field experiments. The derived parameters (e.g. ED₅₀) can compare selectivity and efficacy at numerous cropping systems. © 2018 Society of Chemical Industry