Resistance ofEchinochloa crus-galliPopulations to Acetolactate Synthase-Inhibiting Herbicides

Abstract

ThreeEchinochloa crus-galli(barnyardgrass) populations from rice fields in Arkansas (AR1 and AR2) and Mississippi (MS1), USA, were recently confirmed to be resistant to imazethapyr. Experiments were conducted to characterize cross-resistance to acetolactate synthase- (ALS-) inhibiting herbicides and determine if malathion, a known cytochrome P450 monooxygenase (CYP) inhibitor, would overcome resistance. The AR1 and MS1 populations were cross-resistant to bispyribac-sodium; however, AR2 was sensitive to bispyribac-sodium. The AR1, AR2, and MS1 populations were >94, >94, and 3.3 times, respectively, more resistant to imazamox; >94, 30, and 9.4 times, respectively, more resistant to penoxsulam; and 15, 0.9, and 7.2 times, respectively, more resistant to bispyribac-sodium compared to a susceptible population. Addition of malathion to penoxsulam reduced dry weight of all populations and increased mortality of AR2 and MS1 populations compared to penoxsulam alone. Addition of malathion to imazethapyr and bispyribac-sodium increased the mortality of MS1 population in mixture with imazethapyr and AR1 population in mixture with bispyribac-sodium compared to treatments with imazethapyr and bispyribac-sodium applied alone. Synergism of ALS-inhibiting herbicides with malathion indicates increased herbicide degradation by CYP as partial mechanism of resistance to penoxsulam in all resistant populations and probably to imazethapyr in MS1 and bispyribac-sodium in AR1 populations.

The challenge of herbicide resistance around the world: a current summary

“…Setaria and Avena resistant to ACCase herbicides are commonly found in the north central USA and the Canadian prairies . Resistant L. multiflorum is problematic in many wheat‐growing areas across North America, and GR and ALS‐resistant grasses are found in both row crops and cereals across the continent …”

“…129 Resistant L. multiflorum is problematic in many wheat-growing areas across North America, and GR and ALS-resistant grasses are found in both row crops and cereals across the continent. [130][131][132][133][134][135][136] GR is probably the most widespread and economically impactful resistance across a large swath of North America. GT varieties of maize, soybean and cotton account for >90% of the area planted to those crops.…”

First report of resistance to acetolactate‐synthase‐inhibiting herbicides in yellow nutsedge (Cyperus esculentus): confirmation and characterization

“…6,7 Introduction of imidazolinone (IMI)-resistant rice and overreliance on ALS-inhibiting herbicides for several years has led to the evolution of ALS-resistant weeds in midsouthern United States rice. 8 Several reports of ALS-inhibiting herbicide-resistant weeds such as barnyardgrass (Echinochloa crus-galli L.), 9 smallflower umbrella sedge (Cyperus difformis L.) 10 and rice flatsedge (Cyperus iria L.) 11 have been documented in Arkansas rice, which demonstrates considerable adaptive evolution of these weed species to ALS inhibitors. In 2012, a rice grower in Arkansas failed to control yellow nutsedge with halosulfuron.…”

Herbicidal activity on acetolactate synthase‐resistant barnyardgrass (Echinochloa crus‐galli) in Arkansas, USA

“…() and Riar et al . () for other barnyardgrass accessions that were collected in Mississippi and Arkansas, where multiple applications of imazethapyr at the labeled rate failed to control barnyardgrass.…”