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ARS Home » Midwest Area » Urbana, Illinois » Global Change and Photosynthesis Research » Research » Publications at this Location » Publication #350103
Title: Quantifying resistance to isoxaflutole and mesotrione and investigating their interaction with metribuzin POST in waterhemp (Amaranthus tuberculatus)

Author
item O'BRIEN, SARAH - University Of Illinois
item Davis, Adam
item RIECHERS, DEAN - University Of Illinois

Submitted to: Weed Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/20/2018
Publication Date: 9/11/2018
Citation: O'Brien, S.R., Davis, A.S., Riechers, D.E. 2018. Quantifying resistance to isoxaflutole and mesotrione and investigating their interaction with metribuzin POST in waterhemp (Amaranthus tuberculatus). Weed Science. 66(5):586-594. https://doi.org/10.1017/wsc.2018.36.
DOI: https://doi.org/10.1017/wsc.2018.36

Interpretive Summary: Weed populations that have evolved resistance to multiple herbicides pose a growing threat to agricultural productivity. Common waterhemp (Amaranthus rudis), a dominant weed of corn and soybean cropping systems in the upper Midwest, has repeatedly evolved multiple resistance to different combinations of herbicide chemistries, with some populations reaching five-way multiple resistance. Understanding how common waterhemp, and other weeds, defeat herbicides and evolve resistance is critical for herbicide stewardship. In this study, we quantified the interactive effect of mesotrione (an HPPD inhibiting herbicide) and metribuzin (a Photosystem II inhibiting herbicide) on common waterhemp to determine whether these herbicides, when applied in combination, produce a synergistic effect on waterhemp survival (more mortality than would be expected if the two herbicides did not interact). Dose response assays indicated that the two herbicides acted synergistically at low rates, and additively at higher rates. This synergism suggests that herbicide mixtures that tie up weeds’ ability to detoxify herbicides may hold promise for increasing herbicide efficacy in multiple resistant weed populations.

Technical Abstract: Previous research reported resistance to mesotrione (MES) and other 4-hydroxyphenylpyruvate dioxygenase (HPPD)-inhibiting herbicides in waterhemp (Amaranthus tuberculatus). Experiments were conducted to quantify resistance levels to MES and isoxaflutole (IFT) in NEB (for Nebraska HPPD-resistant) and SIR (for Stanford, Illinois HPPD-resistant) waterhemp populations, which differ in their field-use histories resistance levels to MES. Foliar responses were compared to ACR (HPPD-sensitive but metabolic atrazine-resistant) and SEN (herbicide sensitive). A greenhouse dose-response study was conducted with each herbicide at two postemergence (POST) timings: EPOST (5-cm or 4-5 true leaves) and POST (10-cm or 8-9 true leaves). SIR was 10-fold resistant to IFT and 32-fold resistant to MES EPOST, while NEB was 4-fold resistant to IFT and 7-fold resistant to MES EPOST compared to ACR. Furthermore, SIR was 17-fold resistant to IFT and 21-fold resistant to MES POST, while NEB was 3-fold resistant to IFT and 7-fold resistant to MES POST compared to ACR. Overall these findings indicated greater fold-resistance to MES relative to IFT within each timing. However, POST treatments to SIR showed contrasting effects on resistance levels relative to EPOST. To investigate potential management strategies for resistant waterhemp populations in the field, a POST interaction study was conducted using combinations of metribuzin and either IFT or MES. Following initial dose-response analysis with metribuzin, 191 g ai/ha was chosen for interaction studies since this rate caused an approximate 20% biomass reduction. Metribuzin was combined with 0x, 0.5x, 1x, or 2x field-use rate of either IFT or MES. Results indicated that 52.5 g ai/ ha MES combined with 191 g ai/ha metribuzin displayed a synergistic effect on biomass reduction in SIR. However, other combinations of either MES or IFT and metribuzin resulted in additive effects on biomass reduction in both HPPD-resistant populations. These results give insight into the joint activity between HPPD- and PSII-inhibitors for controlling metabolism-based, multiple herbicide-resistant waterhemp.