Peanut Response to Flumioxazin and S-Metolachlor Under High Moisture Conditions

Abstract

ABSTRACT Georgia produces nearly 51% of the United States peanut (Arachis hypogaea L.) crop. To combat and prevent weed infestations, herbicide programs containing flumioxazin and S-metolachlor are often applied preemergence (PRE). Despite herbicide effectiveness for weed control, peanut injury following heavy rainfall can be problematic. The objective of this study was to evaluate the impact of injury from flumioxazin and S-metolachlor after simulated heavy rainfall events on peanut growth and yield. Plots were planted at the University of Georgia Ponder Research Farm located near Ty Ty, Georgia using conventional tillage practices and twin-row spacing. Treatments included PRE applications of flumioxazin at 0, 0.11 and 0.22 kg ai/ha alone or in combination with S-metolachlor at 0, 1.07, 1.40, 2.80 kg ai/ha and were applied using a CO2-pressurized backpack sprayer. Irrigation and rainfall were ≥20 cm in the 30 days after planting (DAP) to simulate heavy rainfalls. Flumioxazin at 0.22 kg ai/ha caused the greatest visual injury (>60%) and most whole-plant fresh weight/m reductions at 21 DAP compared to other treatments. Peanut density was not impacted by flumioxazin or S-metolachlor. Neither flumioxazin nor S-metolachlor affected J-rooting. Yield was not reduced by any rate of flumioxazin. However, S-metolachlor at 2.80 kg/ha, (2.6X field rate), reduced yields by 8.9% compared to plots where no S-metolachlor or recommended field rates were applied.