Interval Between Sequential Herbicide Treatments for Sourgrass Management

Abstract

More than one herbicide application is usually necessary to manage glyphosate-resistant sourgrass in advanced stages of development efficiently during off-season fallow periods. The objective of this study was to determine the best interval between two sequential applications to control sourgrass, based on the number of days and tiller-height after the first treatment. Two experiments were conducted based on these criteria. Experiment 1 consisted of one application of glyphosate + clethodim (1140 ae ha-1 + 108 g ha-1) followed by glyphosate + clethodim or paraquat (400 g ai ha-1) at an interval of 10, 17, 24, 31, 28, or 45 days. Experiment 2 was conducted with the same herbicide treatments, but using the tiller-height as the criteria for the second application, which were 2-5, 6-10, 11-20, 21-30, and >30 cm. None of the treatments resulted in total sourgrass control during the evaluation period. Overall, treatments with glyphosate + clethodim in the second application were more efficient than paraquat. The most effective interval between sequential applications of glyphosate + clethodim was observed at 17 to 24 days. For paraquat, the best interval for the second application was 6-10 days. The most effective performances based on the tiller-height were found at 620 cm tall for glyphosate + clethodim and 6-10 cm tall for paraquat.

Chemical control of multiple herbicide-resistant Amaranthus: A review

“…Diquat is a non-selective broad-spectrum contact herbicide that is recommended in burndown applications in both agricultural and nonagricultural areas (Gitsopoulos et al, 2014). This herbicide also has limited translocation and should be used on small plants at the early stage of development or in a sequential application following the first application with a systemic herbicide (Mendes et al, 2020).…”

Chemical and cultural management strategies for glyphosate-resistant sourgrass in central Brazil

“…This led to several studies aiming to understand the dynamics of biotypes of the species, focusing on their biology or management (Martins et al, 2017;Pereira et al, 2017;Ferreira et al, 2018;Marochi et al, 2018;Silveira et al, 2018). In agricultural fields, treatments based on ACCase-inhibiting herbicides, such as clethodim and haloxyfop-p-methyl, became the most applied because they were considered effective for the control of adult glyphosate-resistant sourgrass plants when combined or not with other management strategies (Cassol et al, 2019;Mendes et al, 2020;Nunes et al, 2021;Raimondi et al, 2020;. However, chemical control actions for resistant sourgrass should include herbicides from other mechanisms of action and not only ACCase inhibitors, or, at least, a rotation of chemical groups (cyclohexanedione and aryloxyphenoxypropionate, for example) in order to delay the cross-resistance selection that occurs to herbicides from different chemical groups but with the same mechanism of action (Vidal et al, 2006;Nunes et al, 2022).…”