Chemical management of aquatic macrophytes under simulated floodplain condition in mesocosms

Abstract

Floating natives (Eichhornia crassipes and Pistia stratiotes) and emergent exotic invasives (Hedychium coronarium and Urochloa arrecta) macrophytes grow as aquatic weeds in both natural and artificial floodplain areas in Brazil, where the chemical control should be researched. The herbicides glyphosate and saflufenacil, alone or mixed, were tested for weed control under simulated floodplain condition in mesocosms. Glyphosate (1,440 g ha⁻¹), saflufenacil (120 g ha⁻¹), or glyphosate (1,440 g ha⁻¹) + saflufenacil (42, 84, and 168 g ha⁻¹) were applied firstly; and 75 days after treatment (DAT), glyphosate (1,680 g ha⁻¹) was applied as a follow-up treatment to control plant regrowth. An herbicide-free check was also used. Echhinornia crassipes was the species most susceptible to the different herbicides. Saflufenacil alone presented the lowest control on the macrophytes (≤45%) from 7 to 75 DAT, and in most cases they presented high regrowth rates, i.e., this herbicide was the least effective treatment in reducing the dry mass production of the macrophyte community. Glyphosate alone presented low efficacy to control H. coronarium (30–65%), but for the other macrophytes, it presented control peaks ≥90%, maintaining control levels ≥50% until 75 DAT. Glyphosate + saflufenacil, regardless rate of saflufenacil, caused similar damage to glyphosate in E. crassipes and P. stratiotes; however, in U. arrecta it caused 20–30% less injury. In contrast, these treatments provided the best control of H. coronarium. The complementary application of glyphosate was essential to improve the level of control of the first application, after plant regrowth.

Keywords:

• Aquatic weeds
• glyphosate
• plant regrowth
• saflufenacil
• weed management

Acknowledgments

This research did not receive any specific grant from funding agencies in the public, commercial, or not-for-profit sectors.

Disclosure statement

Authors have no competing interest to declare.

Data availability statement

The authors confirm that the data supporting the findings of this study are available within the article.

Additional information

Funding

Authors thank Fundação de Apoio a Pesquisa, Ensino e Extensão (FUNEP) for supporting part of this research in the form of a scholarship to the first author.