Assessing Glyphosate Injury and Forage Bermudagrass Regrowth Using Canopeo

Visual injury estimates are criticized for their subjective nature. Thus, a quantitative method might improve glyphosate injury assessment. This study aimed to develop a quantitative method to determine glyphosate injury on two bermudagrass [Cynodon dactylon (L.) Pers.] cultivars, ‘Greenfield’ and ‘Goodwell’, based on a Canopeo-based green canopy cover reduction (GCCR) method. The experimental design was a completely randomized factorial containing the two bermudagrass cultivars and five glyphosate rates (0.39, 0.53, 1.06, 1.54, and 3.08 kg a.i. ha−1) plus a nontreated control. Visual green canopy cover and GCCR ratings were measured at 8, 16, and 24 days after glyphosate application (DAG). The commonly used visual rating and the Canopeo-based GCCR method correlated. Bland–Altman analysis showed that at low glyphosate rates (0.39 and 0.53 kg a.i. ha−1), the GCCR method overestimated injury compared to visual ratings, while at higher rates (1.54 and 3.08 kg a.i. ha−1), GCCR underestimated injury values by over 30% for Greenfield and 40% for Goodwell. Despite these inconsistencies, both methods yielded similar conclusions. Further research is needed to validate the Canopeo-based GCCR method for other weed species in addition to traditional visual ratings.