Theses and Dissertations
Issuing Body
Mississippi State University
Advisor
Reynolds, Daniel B.
Committee Member
Dodds, Darrin M.
Committee Member
Shaw, David R.
Committee Member
Phillips, J. Mike
Committee Member
Cox, Michael S.
Date of Degree
8-12-2016
Document Type
Dissertation - Open Access
Major
Weed Science
Degree Name
Doctor of Philosophy
College
College of Agriculture and Life Sciences
Department
Department of Plant and Soil Sciences
Abstract
Field, greenhouse and laboratory experiments were implemented to investigate the effects of auxin herbicides on growth and yield of cotton in glyphosate based systems. Field experiments evaluated the effect of rate and timing of dicamba or 2,4-D exposure when applied in glyphosate-resistant cotton. Increasing rates of either dicamba or 2,4-D resulted in increased injury and yield reductions. Initial injury symptomology was similar for cotton exposed at vegetative and reproductive stages. When cotton was exposed to auxin herbicides during vegetative growth, injury increased with time, while foliar injury during reproductive growth was stagnant and often decreased with time. Subsequently, the strongest correlations to yield loss and injury were from later evaluations of vegetative timings. Recovery from injury due to auxin herbicide exposure was dependent upon favorable environmental conditions; however, recovery was often superficial and masked significant yield loss. Greenhouse studies evaluated the impact of the diglycolamine dicamba salt on the movement of 14C radio-labeled potassium salt glyphosate in barnyardgrass and johnsongrass. Increasing glyphosate rate increased total absorption of glyphosate in both species. Total absorption of glyphosate was not impacted by the presence of dicamba, for either johnsongrass or barnyardgrass. Dicamba did not consistently alter the translocation of glyphosate in johnsongrass; however, dicamba did reduce glyphosate translocation in barnyardgrass. Total amount of translocated glyphosate was 2.6 to 4.6% and 3.8 to 6.8% of applied in barnyardgrass and johnsongrass, respectively. Reduced translocation in barnyardgrass was a result of increased glyphosate accumulation in the distal portion of the treated leaf. Increasing the rate of glyphosate did overcome the dicamba induced antagonism; however, altered translocation of glyphosate has been documented to be a precursor to herbicide resistance.
URI
https://hdl.handle.net/11668/21028
Recommended Citation
Smith, Chad Lee, "Auxin Herbicide Effects on Glyphosate Efficacy and Cotton (Gossypium Hirsutum) Yield" (2016). Theses and Dissertations. 832.
https://scholarsjunction.msstate.edu/td/832