Confirmation and Control of Triazine and 4-Hydroxyphenylpyruvate Dioxygenase-Inhibiting Herbicide-Resistant Palmer Amaranth (Amaranthus palmeri) in Nebraska

Abstract

Palmer amaranth is a difficult-to-control broadleaf weed that infests corn and soybean fields in south-central and southwestern Nebraska and several other states in the United States. The objectives of this research were to confirm triazine and 4-hydroxyphenylpyruvate dioxygenase (HPPD)-inhibiting herbicide-resistant Palmer amaranth in Nebraska and to determine sensitivity and efficacy of POST-applied corn herbicides for control of resistant and susceptible Palmer amaranth biotypes. Seeds from a putative HPPD-resistant Palmer amaranth biotype from Fillmore County, NE were collected from a seed corn production field in fall 2010. The response of Palmer amaranth biotypes to 12 rates (0 to 12×) of mesotrione, tembotrione, topramezone, and atrazine was evaluated in a dose–response bioassay in a greenhouse. On the basis of the values at the 90% effective dose (ED90) level, the analysis showed a 4- to 23-fold resistance depending upon the type of HPPD-inhibiting herbicide being investigated and susceptible biotype used for comparison. This biotype also had a 9- to 14-fold level of resistance to atrazine applied POST. Results of a POST-applied herbicide efficacy study suggested a synergistic interaction between atrazine and HPPD-inhibiting herbicides that resulted in > 90% control of all Palmer amaranth biotypes. The resistant biotype had a reduced sensitivity to acetolactate synthase inhibiting herbicides (halosulfuron and primisulfuron), a photosystem-II inhibitor (bromoxynil), and a protoporphyrinogen oxidase inhibitor (fluthiacet-methyl). Palmer amaranth biotypes were effectively controlled (≥ 90%) with glyphosate, glufosinate, and dicamba, whereas 2,4-D ester provided 81 to 83% control of the resistant biotype and > 90% control of both susceptible biotypes.

Confirmation and Control of HPPD-Inhibiting Herbicide–Resistant Waterhemp (Amaranthus tuberculatus) in Nebraska

“…Palmer amaranth resistant to HPPD-inhibiting herbicides has also been confirmed in Nebraska (Jhala et al 2014) and Kansas (Thompson et al 2012). In Nebraska, it was reported that Palmer amaranth sprayed when 10 cm tall was most resistant to topramezone (14-to 23-fold), followed by tembotrione (4-to 6-fold), and mesotrione (4-fold) (Jhala et al 2014). …”

“…Furthermore, multiple resistant populations of waterhemp in Illinois also exhibited various resistance levels to mesotrione, ranging 10-to 35-fold, depending upon the susceptible population used for comparison (Hausman et al 2011). Palmer amaranth resistant to HPPD-inhibiting herbicides has also been confirmed in Nebraska (Jhala et al 2014) and Kansas (Thompson et al 2012). In Nebraska, it was reported that Palmer amaranth sprayed when 10 cm tall was most resistant to topramezone (14-to 23-fold), followed by tembotrione (4-to 6-fold), and mesotrione (4-fold) (Jhala et al 2014).…”

Distribution of glyphosate‐resistant Amaranthus spp. in Nebraska

“…Jhala et al . reported a Palmer amaranth population with multiple resistance to herbicides that target HPPD and photosystem II in Nebraska . GR Palmer amaranth was also reported in Arkansas, Tennessee, Mississippi, North Carolina, New Mexico, and other states…”

Growth Stage Affects Dose Response of Selected Glyphosate-Resistant Weeds to Premix of 2,4-D Choline and Glyphosate (Enlist Duo™ Herbicide*)

“…Additionally, with the evolution of multiple-herbicide-resistant weeds, such as common waterhemp (Bell et al, 2013;Sarangi et al, 2014), kochia (Beckie et al, 2013), and Palmer amaranth (Jhala et al, 2014b), growers' options for effective POST herbicides have dwindled (Tranel et al, 2011). New multiple herbicide-resistant crop technologies can diversify existing herbicide programs by bringing together conventional herbicide chemistries, some of which, such as 2,4-D, are not labeled for POST application in soybean (Craigmyle et al, 2013a(Craigmyle et al, , 2013b.…”