Articles
Preemergence herbicide control of Benghal dayflower produced from subterranean flower seeds sown at four depths
Article number
1104_60
Pages
407 – 414
Language
English
Abstract
In the US, Benghal dayflower (Commelina benghalensis L.) is listed as a noxious weed by nine states as well as the federal government.
Its presence in plant nurseries can result in quarantining and prohibition of plant sales.
This glyphosate-tolerant, herbaceous perennial is unusual because it produces below-ground, cleistogamous flowers.
Seeds from subterranean flowers are relatively large and produce seedlings that can be well-developed before reaching the growing medium surface.
This reduces its control by preemergence herbicides.
The objective of this research was to evaluate the efficacy of preemergence herbicides (labelled for ornamental crops) in controlling Benghal dayflower subterranean flower seeds germinating from various depths in a commercial container growing medium.
Twenty subterranean seeds were sown on the surface of or buried at one of three depths (2, 4, 6 cm) in the growing medium.
Two pots of each sowing depth were used per plot and treatments were replicated five or six times.
Besides the water only control, there were six herbicide treatments (g a.i. ha-1): dimethenamid-P (1,680); indaziflam (84); S-metolachlor (2,135); flumioxazin (429); pyroxasulfone (164); and flumioxazin + pyroxasulfone (194 + 164). Pot weed coverage estimates were recorded at 4 weeks after treatment.
Weed dry biomasses were determined after the pot coverage evaluation.
All preemergence herbicide treatments were effective in controlling Benghal dayflower sown on the medium surface; however, there were significant interactions between herbicides and burial depth.
Indaziflam provided unacceptable control when seeds were buried.
Weed control when seeds were sown at 2 cm was good to excellent in the dimethenamid-P, flumioxazin, and flumioxazin + pyroxasulfone treatments.
Fair control when seeds were sown at 2 cm was observed in the pyroxasulfone- and S-metolachlor-treated pots.
Control of seeds sown at 4 and 6 cm was significant only in treatments containing flumioxazin.
Further testing is needed to see if there is synergy between flumioxazin and pyroxasulfone and whether other herbicides with the same mechanism of action as flumioxazin are also effective in controlling subterranean seeds germinating below the medium surface.
Its presence in plant nurseries can result in quarantining and prohibition of plant sales.
This glyphosate-tolerant, herbaceous perennial is unusual because it produces below-ground, cleistogamous flowers.
Seeds from subterranean flowers are relatively large and produce seedlings that can be well-developed before reaching the growing medium surface.
This reduces its control by preemergence herbicides.
The objective of this research was to evaluate the efficacy of preemergence herbicides (labelled for ornamental crops) in controlling Benghal dayflower subterranean flower seeds germinating from various depths in a commercial container growing medium.
Twenty subterranean seeds were sown on the surface of or buried at one of three depths (2, 4, 6 cm) in the growing medium.
Two pots of each sowing depth were used per plot and treatments were replicated five or six times.
Besides the water only control, there were six herbicide treatments (g a.i. ha-1): dimethenamid-P (1,680); indaziflam (84); S-metolachlor (2,135); flumioxazin (429); pyroxasulfone (164); and flumioxazin + pyroxasulfone (194 + 164). Pot weed coverage estimates were recorded at 4 weeks after treatment.
Weed dry biomasses were determined after the pot coverage evaluation.
All preemergence herbicide treatments were effective in controlling Benghal dayflower sown on the medium surface; however, there were significant interactions between herbicides and burial depth.
Indaziflam provided unacceptable control when seeds were buried.
Weed control when seeds were sown at 2 cm was good to excellent in the dimethenamid-P, flumioxazin, and flumioxazin + pyroxasulfone treatments.
Fair control when seeds were sown at 2 cm was observed in the pyroxasulfone- and S-metolachlor-treated pots.
Control of seeds sown at 4 and 6 cm was significant only in treatments containing flumioxazin.
Further testing is needed to see if there is synergy between flumioxazin and pyroxasulfone and whether other herbicides with the same mechanism of action as flumioxazin are also effective in controlling subterranean seeds germinating below the medium surface.
Authors
R.H. Stamps
Keywords
Commelina benghalensis, dimethenamid-P, flumioxazin, indaziflam, S-metolachlor, pyroxasulfone, tropical spiderwort, weed
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