Assessing herbicide symptoms by using a logarithmic field sprayer.

Area of Science:

• Agricultural Science
• Weed Science
• Agronomy

Background:

• Herbicide selectivity and efficacy assessment in field trials often overlooks dose-response regressions.
• Logarithmic sprayers offer automated, precise herbicide rate dilutions.

Purpose of the Study:

• To demonstrate the utility of logarithmic sprayers in extracting biologically relevant parameters for herbicide efficacy.
• To compare herbicide performance across different locations and assessment timings using dose-response data.

Main Methods:

• Field experiments were conducted in conventional and organic systems with canola, white mustard, and no crop plots.
• Herbicides diflufenican and beflubutamid were applied using a logarithmic sprayer.
• Mixed-effect log-logistic dose-response regression models analyzed visual and Excess Green Index data.

Main Results:

• Effective Dose 50% (ED50) values varied by herbicide, location, and crop at different days after treatment (DAT).
• Excess Green Index data showed differences in ED90 for beflubutamid on white mustard and canola, but not for diflufenican.
• ED50 values for visual assessment indicated location-specific differences for beflubutamid and crop-specific differences for diflufenican.

Conclusions:

• Nonlinear regression models effectively analyze dose-response data from logarithmic sprayers in field settings.
• Derived parameters like ED50 facilitate comparisons of herbicide selectivity and efficacy in diverse cropping systems.