Application of Preemergence and Postemergence Herbicides for Controlling Henbit (Lamium amplexicaule L.) in the Upper Coastal Area of Texas

Abstract

Background and Aims: Timely fall herbicide applications are an important management strategy for winter annual weeds, balancing erosion control benefits with the need to optimize spring planting conditions and early crop growth. Studies were conducted to evaluate herbicide programs for control of henbit under fallow conditions. Study Design:  Randomized complete block design (RCBD) with 3 replications. Place and Duration of Study: Upper Coastal area of Texas near Ganado during the 2015 through 2017 growing seasons. Methodology: Postemergence herbicide applications were carried out using a CO₂-pressurized backpack sprayer equipped with TeeJet 11002 flat-fan nozzles, operated at a pressure of 180 kPa and calibrated to deliver 187 L ha⁻¹. An untreated control was included at each experimental site for comparative purposes. Henbit control was assessed visually using a rating scale ranging from 0 to 100, where 0 represented no observable control and 100 denoted complete control or plant mortality. Treatment means were separated using Fisher’s Protected Least Significant Difference (LSD) test at the 5% probability level. Results: When evaluated early-season, 31 to 42 days after herbicide application (DAA), herbicide systems containing either atrazine or flumioxazin controlled henbit 97 to 100%.  When the evaluation was taken 19 DAA, henbit control with atrazine systems without flumioxazin was poor with control ranging from 47 to 57% while flumioxazin systems, with the exception of flumioxazin + thifensulfuron-methyl + tribenuron-methyl + glyphosate, provided at least 90% henbit control.  When evaluated 57 to 75 DAA, the combination of flumioxazin + pyrosulfone with or without atrazine provided 93 to 100% control.  Rimsulfuron + thifensulfuron-methyl alone or in combination with atrazine and atrazine + flumioxazin controlled henbit 80 to 98% while rimsulfuron + thifensulfuron-methyl + glyphosate provided 78 to 96% control. Conclusion: Several herbicide programs provided satisfactory to excellent henbit control and are options for reducing the winter weed issue. Flumioxazin + pyroxasulfone alone or in combination with atrazine provided the most consistent control.  These combinations not only provide ‘knock-down’ of the henbit but also can provide residual control.