Improved efficiency of an herbicide combining bentazone and terbuthylazine – can weeds be controlled with better environmental safety?

Abstract

Chemical herbicides have been extensively used in agriculture to control the negative impacts of weeds in crops to improve agricultural yields. Authorized herbicidal active ingredients (AIs) have been combined in multiple ways to produce distinct commercial formulations targeting diverse weeds. However, interactions between AIs and co-formulants can result in unpredictable outcomes. In addition, the efficacy against target weeds of application rates much lower than those commercially recommended has been reported. In this context, the present work intends to assess the possibility of optimizing the combination of AIs within a commercial formulation of bentazone and terbuthylazine towards alternatives with decreased environmental hazardous potential, by considering both the mixture composition and application rates. The putative interaction between bentazone and terbuthylazine (AIs), as formulated within a commercial product and in alternative ratios and rates, was assessed, first, by testing with selected aquatic (Raphidocelis subcapitata) and terrestrial (Brassica napus) non-target sensitive indicators for environmental safety assessment, and then, by assessing the corresponding efficacy against a major target weed (Portulaca oleracea). Results showed that (i) commercially recommended rates represent a remarkable potential risk to soil and also aquatic ecosystems; (ii) application rates 10-fold lower than recommended are effective in the control of the main target weed; and (iii) a one-way formulation including only bentazone, which is already available on the market, seems to represent an environmentally safer alternative to the two-way formulation in the control of P. oleracea. These outcomes suggest that a more systematic assessment of the ecotoxicity, as well as the efficacy, of the combinations of pesticides used in commercial products during design stages could ensure a good performance of the agrochemicals against the targets, while improving their environmental safety regarding impacts in non-target organisms.