Multi-mixture herbicides provide management strategies in the control of the aquatic weed Heteranthera reniformis

Abstract

Heteranthera reniformis (mud plantain) is a weed of aquatic habit, which currently causes losses in the production of ornamental plants and irrigated crops, such as rice, and for which there are no herbicides registered in Brazil with proven control effectiveness. This study evaluated the control effectiveness of individual and multi-mixture herbicides (i.e., glyphosate, 2,4-D, triclopyr, paraquat, oxyfluorfen, sulfentrazone, carfentrazone, diuron and S-metolachor) on post-emergence of mud plantain. An organosilicone spreader adjuvant was also evaluated. Weed injury assessments were carried out over time, at 7, 14, 21, 42, and 60 days after application (DAA) of the herbicides. At the end of the study (60 DAA), the weed dry matter was measured. The progress of weed injury was modeled using a time-trend decomposition procedure based on the LOcally wEighted Scatterplot Smoothing (LOESS) method. Treatments with glyphosate application proved to be more effective in relation to mud plantain injury over time, with a slight emphasis on treatments associated with triclopyr. However, evaluating the dry matter, the treatment with glyphosate alone was more effective; besides, it showed short-range injury variance in the control of H. reniformis. The inclusion of organosilicone adjuvant to some treatments was not quite successful. Regardless of the herbicide used, higher levels of initial injury are a fair predictor of final control effectiveness (i.e., period after the herbicide effect). On the other hand, less initial injury corresponded directly to low control effectiveness. The results suggest that the herbicides, glyphosate, triclopyr, and carfentrazone, are suitable for mud-plantain control.