Characterization of a waterhemp (Amaranthus tuberculatus) population from Illinois resistant to herbicides from five site-of-action groups

Authors: EVANS, CODY - University Of Illinois; STROM, SETH - University Of Illinois; RIECHERS, DEAN - University Of Illinois; Davis, Adam; TRANEL, PATRICK - University Of Illinois; HAGER, AARON - University Of Illinois

Submitted to: Weed Technology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/21/2019
Publication Date: 5/23/2019
Citation: Evans, C.M., Strom, S.A., Riechers, D.E., Davis, A.S., Tranel, P.J., Hager, A.G. 2019. Characterization of a waterhemp (Amaranthus tuberculatus) population from Illinois resistant to herbicides from five site-of-action groups. Weed Technology. 33(3):400-410. https://doi.org/10.1017/wet.2019.19.
DOI: https://doi.org/10.1017/wet.2019.19

Interpretive Summary: Weeds that evolve multiple herbicide resistance are able to survive exposure to herbicides from more than one site of action group, including mixtures of herbicides. The number of multiple herbicide resistant genotypes has grown worldwide, with many weed species and herbicide sites of action represented. In the US, one species in particular, tall waterhemp (Amaranthus tuberculatus) has been particularly adept at evolving multiple herbicide resistances. In 2012, a waterhemp population resistant to herbicides from several site-of-action (SOA) groups was discovered in a corn field in central Illinois. Sequence analyses confirmed target-site-based resistance to acetolactate synthase (ALS) and protoporphyrinogen oxidase (PPO)- inhibiting herbicides and greenhouse dose-response experiments confirmed resistance to the 4-hydroxyphenylpyruvate dioxygenase (HPPD) inhibitor mesotrione, the synthetic auxin 2,4-D, and the photosystem II inhibitor atrazine. Complementary results from field, laboratory, and greenhouse investigations indicate that this waterhemp population has evolved resistance to herbicides from a total of five SOAs, including ALS-, PPO-, PSII-, and HPPD-inhibiting herbicides and 2,4-D. Given that this weed population is close to escaping chemical control, it signals a critical need for weed management approaches that are less reliant upon herbicides.

Technical Abstract: Experiments were initiated to characterize a waterhemp population (CHR) discovered in a central Illinois corn field after it was not controlled by the 4-hydroxyphenylpyruvate dioxygenase (HPPD) inhibitor topramezone. Field experiments conducted during 2014–2015 indicated that acetolactate synthase (ALS)-, protoporphyrinogen oxidase (PPO)-, photosystem II (PSII)-, and HPPD-inhibiting herbicides and the synthetic auxin 2,4-D did not control the CHR population. Laboratory experiments confirmed target site–based resistance mechanisms to ALS- and PPO-inhibiting herbicides. Herbicide doses required to reduce dry biomass 50% (GR50) were determined in greenhouse dose–response experiments, and indicated 16-fold resistance to the HPPD inhibitor mesotrione, 9.5-fold resistance to the synthetic auxin 2,4-D, and 252-fold resistance to the PSII inhibitor atrazine. Complementary results from field, laboratory, and greenhouse investigations indicate that the CHR population has evolved resistance to herbicides from five sites of action (SOAs): ALS-, PPO-, PSII-, and HPPD-inhibiting herbicides and 2,4-D. Herbicide use history for the field in which CHR was discovered indicates no previous use of 2,4-D.