Volunteer Peanut (Arachis hypogaea L.) Control in Glyphosate/Glufosinate Resistant Cotton (Gossypium hirsutum L.)

Abstract

The increase in conservation tillage along with the use of herbicide-resistant crops has changed the dynamics of weed populations and control methods with volunteer plants from the previous crop contributing to the weed community in subsequent rotations. In the southeastern U.S., a peanut-cotton rotation is very popular for disease, insect, weed, and nematode suppression; however, volunteer peanut plants can be challenging to control in cotton production. Field experiments were conducted in 2010 at the Gulf Coast and Wiregrass Research and Extension Centers to identify effective control strategies for volunteer peanut in cotton. RoundUp Ready® and LibertyLink® cotton was planted in plots where peanuts were produced in 2009. Plots were sprayed at the cotton’s 2-leaf, 4-leaf, or 2 and 4-leaf growth stage with either a postemergence (POST) glyphosate (1.12 kg ai ha-1) or glufosinate (0.47 kg ai ha-1) application alone or followed by trifloxysulfuron-sodium (0.005 kg ai ha-1) applied at the 8-leaf growth stage. In addition, all plots received prometryn (1.12 kg ai ha-1) + monosodium acid methanearsonate (MSMA) (2.24 kg ai ha-1) as a post-directed spray (LAYBY) to cotton. At the Wiregrass Research and Extension Center, the 2-leaf or 4-leaf alone treatment provided ≤ 30% control. The 4+8-leaf treatment provided poor early control, < 55 %, but control increased to ≥ 65% over time. The best control was observed in the 2+4+8-leaf and 2+8-leaf treatments. However, only 70-75% control was attained in this study indicating significant peanut survival. There was no significant difference in control of volunteer peanuts with glyphosate or glufosinate systems. At the Gulf Coast Research and Extension Center, better overall volunteer peanut control, ranging from 93% to 20% across all treatments, was observed. The only treatment that provided significantly lower control than the weed free treatment at the late rating was the 2-leaf alone application at ≤ 20 % control. At this location there was also an advantage in using a glufosinate system at both 4-leaf and 8-leaf ratings.