Control of Ipomoea grandifolia and antioxidant enzyme activity with bentazon and glyphosate at times and soil water conditions
Helis Marina Salomão, Michelangelo Müzell Trezzi, Fortunato de Bortoli Pagnoncelli Junior, Adriano Suchoronczek, Matheus Viecelli and Katia Cristina Dalpiva Hartmann
Federal University of Technology (UTFPR), Pato Branco, PR Brazil.
Weed management with herbicides requires favorable environmental conditions, that maximize efficiency, such as soil humidity and timing of application. The aim of this study was to assess the effect of the application timing of bentazon and glyphosate herbicides on the control and activity of antioxidant enzymes in Ipomoea grandifolia, under different conditions of soil water availability. Two experiments, one for each herbicide (bentazon and glyphosate), were conducted in a factorial design with four replicates. The first factor was the two rates of each herbicide (504 and 720 g i.a. ha-1 of bentazon and 651 and 911.4 g i.a. ha-1 of glyphosate). The second factor was the six application times (1 am; 5 am; 9 am; 1 pm; 5 pm and 9 pm). The third factor, soil water content (100% and 50% of field capacity). Plus, two controls without herbicide application. At 21 days after application (DAA) of bentazon and 28 DAA of glyphosate, the fresh mass of the aboveground plants was measured. In addition, the activities of the enzymes superoxide dismutase (SOD), catalase (CAT) and peroxidase (POX) were determined. For plants under water restriction, an increase of approximately 20% in fresh mass was observed compared in plants without water restriction, indicating lower control efficiency under water stress condition. For bentazon, at 1 pm has been observed the lowest herbicide efficiency, the other times were the most efficient, and did not differ. For glyphosate, the application at 9 am was the most efficient, while at 1 am provided the worst control efficiency. Higher CAT and SOD activities after bentazon application were observed at 1 pm. Among the three enzymes evaluated, SOD presented the highest activity after glyphosate application. Generally, the times of the day with the highest peak of enzymatic activity were distinct between with and without water restriction.
1. Water restriction reduces the efficiency of bentazon and glyphosate.
2. Better efficiency for bentazon was observed at 1 am, 5 am, 9 am, 5 pm and 9 pm.
3. Better efficiency for glyphosate was observed at 9 am.