Effectiveness and phytotoxicity of selective post-emergent herbicides in the sugarcane variety Mex 68-1345

Resumen

Objective: This study assessed the effectiveness and phytotoxicity of selective post-emergent herbicides for managing major weed species in a tropical agroecosystem.

Design/methodology/approach: A randomised complete block design with four replicates was implemented, testing nine herbicide treatments and one untreated control on the Mex 68-1345 variety. Weed control and crop phytotoxicity were assessed visually at 7, 14, and 21 days after application (DAA) using the EWRS scale. In addition, SPAD chlorophyll index readings were recorded as an indicator of foliar phytotoxicity. The herbicide combinations Ametryn + Atrazine (AMT+ATZ), Ametryn + Atrazine + Diuron (AMT+ATZ+DIU), and Ametryn + 2,4-D (AMT+2,4-D) achieved “adequate control” (87.5-93 %) with mild and transient phytotoxicity (<3.5 %).

Results: A significant negative correlation (P < 0.0001) was observed between herbicide effectiveness and SPAD index values, indicating a physiological cost associated with weed suppression and short-term stress in sugarcane. Environmental conditions particularly low soil moisture (<50 %) and high temperatures (>34 °C) negatively affected herbicide efficacy and favoured weed regrowth.

Limitations on study/implications: The study was conducted under specific environmental conditions and assessed only short-term herbicide effects (up to 21 DAA), without assessing yield or economic return. Species-specific resistance was not confirmed by bioassays. Despite these limitations, the findings provide practical insight into herbicide performance under field conditions and highlight the need for integrated weed management strategies that include environmental monitoring, resistance awareness, and longer-term assessments.

Findings/conclusions: These findings support the strategic use of post-emergent herbicides as a component of integrated weed management (IWM) programmes aimed at sustainable sugarcane production.