Effect of new auxin herbicide formulations on control of herbicide resistant weeds and on microbial activities in the rhizosphere

Authors: Nandula, Vijay; Tyler, Heather

Submitted to: American Journal of Plant Sciences
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/10/2016
Publication Date: 12/13/2016
Citation: Nandula, V.K., Tyler, H.L. 2016. Effect of new auxin herbicide formulations on control of herbicide resistant weeds and on microbial activities in the rhizosphere. American Journal of Plant Sciences. 7:2429-2439.

Interpretive Summary: Widespread distribution of glyphosate-resistant weeds in soybean-growing areas across Mississippi has economically affected soybean planting and follow-up crop management operations. New multiple herbicide-resistant crop (including soybean) technologies with associated formulations will soon be commercialized. Scientists from the Crop Production Systems Research Unit (USDA-ARS), Stoneville, MS conducted greenhouse and laboratory studies to determine the efficacy of new 2,4-D +glyphosate and dicamba formulations on selected herbicide resistant weeds, and to determine the impact of the new 2,4-D + glyphosate formulation on selected microbial communities in the soybean rhizosphere involved in nutrient cycling. New 2,4-D + glyphosate and dicamba formulations registered for use on 2,4-D and dicamba-resistant soybean, respectively, adequately controlled glyphosate resistant and susceptible pigweeds (Palmer amaranth and tall waterhemp) and common ragweed. The 2,4-D + glyphosate formulation did not significantly impact soil microbial activities linked to nutrient cycling in the soybean rhizosphere. These results indicate these new 2,4-D + glyphosate and dicamba formulations can be effective tools for soybean growers of Mississippi in controlling glyphosate resistant weeds while not having adverse effects on the activities of beneficial soil microorganisms and, eventually, soybean yield.

Technical Abstract: Widespread distribution of glyphosate-resistant weeds in soybean-growing areas across Mississippi has economically affected soybean planting and follow-up crop management operations. New multiple herbicide-resistant crop (including soybean) technologies with associated formulations will soon be commercialized. The objectives of this research were to determine the efficacy of new 2,4-D +glyphosate and dicamba formulations on herbicide resistant weeds, and to determine the impact of the new 2,4-D + glyphosate formulation on microbial communities in the soybean rhizosphere involved in nutrient cycling. New 2,4-D + glyphosate and dicamba formulations registered for use on 2,4-D and dicamba-resistant soybean, respectively, adequately controlled glyphosate resistant and susceptible pigweeds (Palmer amaranth and tall waterhemp) and common ragweed. The 2,4-D + glyphosate formulation did not significantly impact soil microbial activities linked to nutrient cycling in the soybean rhizosphere. These results indicate these new 2,4-D + glyphosate and dicamba formulations can be effective in controlling glyphosate resistant weeds while not having adverse effects on the activities of beneficial soil microorganisms.