Differential sensitivity of Kansas Palmer amaranth populations to multiple herbicides

Abstract

A field survey was conducted in 2014 to determine the response of Palmer amaranth (Amaranthus palmeri S. Wats.) populations from 16 counties in southcentral Kansas to commonly used herbicides. The main objective was to evaluate the sensitivity of 28 randomly collected populations to field-use rates of glyphosate, chlorsulfuron, 2,4-D, dicamba, atrazine, and mesotrione herbicides; and further characterize the sensitivity levels in two populations. The response of all tested populations was categorized as less sensitive (≤59% injury), moderately sensitive (60-89% injury), and susceptible (90-100% injury) based on visible injury at 21 days after treatment (DAT). Results from herbicide screening experiments indicated that 47, 36, 7, 75, and 32% of tested populations were less sensitive (putative resistant) to glyphosate, chlorsulfuron, 2,4-D, atrazine, and mesotrione herbicide, respectively. None of the tested populations showed less sensitivity (≤59% injury) to dicamba herbicide. Whole plant dose-response assays on two populations collected from Kiowa (KW2) and Pratt (PR8) counties indicated that the KW2 population had 3.0-, 2.3-, 5.8-, and 8.4-fold less sensitivity to 2,4-D, chlorsulfuron, atrazine, and mesotrione, respectively, compared to a known susceptible (MHS) population. In contrast, the PR8 population was 2.0-, 8.6-, 10.6-, 3.7-, and 2.8-fold less sensitive to 2,4-D, glyphosate, chlorsulfuron, atrazine, and mesotrione, respectively, compared to MHS population. Overall, these results suggest that reduced sensitivity to glyphosate, chlorsulfuron, atrazine, and/or mesotrione is highly prevalent in southcentral Kansas. Growers should adopt diversified weed control methods to manage these difficult-to-control populations on their production fields.Abbreviations: CI, confidence interval; DAT, days after treatment; GR 50 , 50% shoot biomass reduction; HR, herbicide-resistant; MOA, mechanism of action; SI, sensitivity index.

Weeds in Cover Crops: Context and Management Considerations

“…Herbicideresistant horseweed is becoming increasingly problematic in winter grain crops such as wheat in the USA [65,66]. Similarly, herbicide-resistant summer annual weeds such as common ragweed, redroot pigweed, and Palmer amaranth (Amaranthus palmeri S. Watson) are increasing in summer annual crops [67,68]. Suppressive cover crops like cereal rye can help in managing these HR weeds by providing additional control when added to herbicide programs [66,69].…”

Integrating cover crops for weed management in the semiarid U.S. Great Plains: opportunities and challenges

“…Amaranthus palmeri populations in Texas were confirmed resistant to atrazine in 1993, and in Kansas in 1995 (Heap 2019). Populations of A. palmeri resistant to ALS inhibitors and glyphosate are reported across the Southern and Central Great Plains (Figure 1) (Chahal et al 2017;Garetson et al 2019;Horak and Peterson 1995;Kumar et al 2019bKumar et al , 2020Nakka et al 2017). Amaranthus palmeri resistant to 4-hydroxphenylpyruvate dioxygenase-inhibiting herbicides was first confirmed in Kansas in 2009, and subsequently in Nebraska and Texas (Garetson et al 2019;Jhala et al 2014;Singh et al 2018).…”

“…Amaranthus palmeri resistant to 4-hydroxphenylpyruvate dioxygenase-inhibiting herbicides was first confirmed in Kansas in 2009, and subsequently in Nebraska and Texas (Garetson et al 2019;Jhala et al 2014;Singh et al 2018). Additionally, A. palmeri populations with multiple resistance to two, three, four, or five herbicide SOAs have become an increasing concern in the Southern and Central Great Plains (Figure 1) (Garetson et al 2019;Heap 2019;Jhala et al 2014;Kumar et al 2019bKumar et al , 2020Singh et al 2018). More recently, an A. palmeri population with multiple resistance to 2,4-D, glyphosate, chlorsulfuron, mesotrione, and atrazine and reduced sensitivity to fomesafen has been reported in Kansas (Kumar et al 2019b).…”

Susceptibility of Arkansas Palmer amaranth accessions to common herbicide sites of action

“…Herbicide resistance in Palmer amaranth is a significant issue and resistance surveys are commonly used to determine the geographic magnitude of resistance (Bagavathiannan and Norsworthy 2016;Bond et al 2006;Copeland et al 2018;Garetson et al 2019;Kumar et al 2020;Singh et al 2018;Varanasi et al 2018;Wise et al 2009). Alternatively, the efficacy of SOAs can be determined through resistance surveys, which can aid the development and evaluation of current weed management programs (Beckie et al 2000;Burgos et al 2013).…”