Topramezone and carfentrazone + 2,4-D + mecoprop-p + dicamba (SpeedZone®) are herbicides labeled for POST goosegrass (Eleusine indica L. Gaertn.) control in hybrid bermudagrass (Cynodon dactylon × C. transvaalensis Burtt Davy). Field research was conducted in Knoxville, TN, during 2019 and 2020 to evaluate goosegrass control and hybrid bermudagrass tolerance to these herbicides applied alone and in mixture. Treatments included topramezone (12.2 g ha–1), SpeedZone® [carfentrazone (33.6 g ha–1) + 2,4-D (1,029 g ha–1) + mecoprop-p (322 g ha–1) + dicamba (91 g ha–1)] and SpeedZone® + topramezone at 12.2, 6.1, 3.6, or 2.4 g ha–1. A nontreated control was included for comparison. Hybrid bermudagrass tolerance was assessed on four cultivars (‘Northbridge’, ‘Tifway’, ‘Tahoma 31’, and ‘TifTuf’) via visual ratings of turfgrass injury and assessments of normalized difference vegetation index (NDVI). At the termination of the experiment, SpeedZone® alone and in mixture with topramezone controlled goosegrass better than or equal to topramezone alone. Mixtures of SpeedZone® + topramezone reduced injury on all cultivars compared to topramezone alone, particularly when mixtures delivered ≤6.1 g ha–1 topramezone. Injury subsided on all cultivars by 28 d after treatment regardless of herbicide. Findings suggest that SpeedZone® can be mixed with topramezone at the rates tested herein to minimize hybrid bermudagrass injury from topramezone applications for goosegrass control.

Plants of catchweed bedstraw from different Norwegian locations and from three other countries were compared with respect to morphological factors, herbicide sensitivity, and genetic variation. For the morphological comparison of cotyledons, whorls, leaves, and fruits five populations, grown outdoors but sheltered from rain, were used. Plants from Belgium and Sweden showed a high similarity, whereas one Norwegian population differed significantly in nearly all parameters. The same populations were used for a comparison of the sensitivity to the herbicide mecoprop-P. In this study, only slight differences appeared between the five populations. Finally, a deoxyribonucleic acid (DNA) sequence analysis of the internal transcribed spacer (ITS) regions was performed. The entire sequence of the ITS1 and ITS2 and the 5.8S subunit of ribosomal DNA were obtained from 15 populations (12 from Norway and one each from Sweden, Belgium, and Germany). The sequences had a length between 590 and 662 base pairs; intraspecific length variation was observed. Based on six insertions–deletions and 26 nucleotide substitutions, two DNA types could be distinguished. The first type consisted of eight Norwegian populations, whereas the second one contained the other seven populations including all non-Norwegian populations. The sequence alignments were used to build a phylogenetic tree. The results of the morphological comparison mostly corresponded with the results of the ITS sequence analysis. The variation was only to some extent correlated with the geographic distribution of the populations.