Effectiveness of bicyclopyrone alone and in combination with hexazinone for controlling Paspalum maritimum Trind. in pre- and post-emergence

Abstract

Ginger grass (Paspalum maritimum Trind.) is a perennial grass that is difficult to control due to the robustness of its rhizome system. This study aimed to evaluate the effectiveness of the bicyclopyrone herbicide in managing this species under greenhouse (0 to 740 g ha-1) and field [untreated control, picloram alone, and picloram + hexazinone applied at pre- and post-emergence, with assessments at 15, 30, and 45 days after application (DAA) of the green cover index (Canopeo)] conditions. In the greenhouse bioassay, picloram provided 100 % of control starting from 185 g a.i. ha-1. In the field, the pre-emergence application outperformed the post-emergence in all evaluations. At 15 DAA, there was a significant interaction, with the bicyclopyrone + hexazinone mixture standing out with the lowest coverage values: 7.1 % in pre- and 13.6 % in post-emergence, showing synergy between HPPD inhibitors and PSII. At 30 DAA, the mixture maintained the highest level of control; however, there was a linear increase in coverage for all the herbicide treatments due to rhizome regrowth and emergence of new seedlings. At 45 DAA, the reinfestation pressure evened out the plots, with no statistical difference between the treatments and the control. Bicyclopyrone (185 g ha-1) is effective in a controlled environment, but, in the field, mixing it with hexazinone as a pre-emergence treatment is the best management strategy. The effective control lasts only up to 30 days, with coverage returning by 45 DAA, regardless of the application method.

KEYWORDS: Ginger grass, 4-hydroxyphenylpyruvate dioxygenase inhibitor herbicides, rhizomes.