ARS | Publication request: Metolachlor formulation and ground cover effects on cotton and weed growth

Submitted to: Proceedings of Southern Weed Science Society
Publication Type: Abstract Only
Publication Acceptance Date: January 3, 2009
Publication Date: N/A

Technical Abstract: Metolachlor is an important tool for managing glyphosate-resistant pigweeds. Cover crop residues in conservation tillage impede the effectiveness of metolachlor. Greenhouse experiments were conducted to evaluate the influence of cover crops with the following ground covers: no cover, full cover, and simulated strip tillage. Pots were filled with Tifton sandy loam. Rye mulch was collected by clipping plants to the ground and air dried, representing a full ground cover in a no-tillage system. Cotton, Palmer amaranth, and cereal rye were planted to a depth of 0.2 to 1.3 cm. Metolachlor (1.4 kg ai/ha) treatments were applied by impregnation on a clay-alginate bead (MTC), on 10-10-10 fertilizer (IFRT), or sprayed using a water carrier (standard application method). Data measurements included stand counts, plant width, canopy height, and biomass. Cotton emergence was 92% for spray treatments, 82% for IFRT, and reduced to 72% by MTC. Effective weed control was demonstrated by inhibiting Palmer amaranth and rye emergence across all metolachlor treatments. Cotton emergence was 95% for no cover and 80% for full mulch cover. Metolachlor is not currently registered for PRE application in cotton, due to excessive crop injury. Instead, metolachlor must be applied following cotton emergence, but prior to weed germination. Metolachlor is a valuable alternative mode-of-action to control glyphosate and/or ALS-resistant Palmer amaranth in cotton, controlling weedy species prior to emergence.