Management of ACCase-Inhibiting Herbicide-Resistant Smooth Barley (Hordeum glaucum) in Field Pea with Alternative Herbicides

Abstract

Smooth barley is an annual weed species that is infesting crops and pastures in South Australia. Complicating control options is the presence of herbicide-resistant biotypes. A field trial was conducted to identify alternative herbicides for the management of acetyl coenzyme A carboxylase (ACCase)-inhibiting herbicide-resistant smooth barley in field pea. Preplant (PP) soil applications of pyroxasulfone; prosulfocarb plus S-metolachlor; dimethenamid-P; propyzamide; trifluralin alone or with triallate or with diuron; or imazamox applied POST were evaluated for their effectiveness and crop safety. Propyzamide, pyroxasulfone, or imazamox applied POST provided a high level of smooth barley control, did not cause any crop injury, and increased field pea grain or forage yield compared with the nontreated. Furthermore, propyzamide or pyroxasulfone reduced panicle density and seed production in smooth barley, whereas the effectiveness of POST imazamox varied over the two seasons. Dimethenamid-P reduced the impact of smooth barley on field pea yield, but cause stunting, and was less effective than propyzamide, pyroxasulfone, and imazamox in reducing smooth barley seed production. Negative relationship between field pea yield and smooth barley panicle density indicated that smooth barley is highly competitive in field pea crops and can cause large yield losses. The results of this investigation suggest that propyzamide or pyroxasulfone applied PP and imazamox applied POST could be used effectively in the field for the management of ACCase-inhibiting herbicide-resistant smooth barley in South Australia.

Basis of ACCase and ALS inhibitor resistance in Hordeum glaucum Steud

“…In order to manage resistant or wild‐type populations, diversified weed management strategies should include crop rotations which enhance crop–weed competition and allow the use of herbicides with different modes of action. Preplant herbicides such as propyzamide and pyroxasulphone could be used effectively to control ACCase‐inhibiting herbicide‐resistant H. glaucum populations . These herbicides also have long residual activity, which is beneficial in extending weed control in dormant populations.…”

“…Preplant herbicides such as propyzamide and pyroxasulphone could be used effectively to control ACCase-inhibiting herbicide-resistant H. glaucum populations. 57 These herbicides also have long residual activity, which is beneficial in extending weed control in dormant populations. Clearfield ™ technology is currently being heavily used by Australian growers for the control of ACCase-resistant H. glaucum.…”

The Impact of Herbicide Application and Defoliation on Barley Grass (Hordeum murinum subsp. glaucum) Management in Mixed Pasture Legumes

“…This would have made counting seeds per inflorescence impossible, as per methods in the defoliation/herbicide experiment. Fecundity (total seed production) was, thus, estimated using methods similar to those described by Shergill, Fleet, Preston, and Gill [24]. Twenty-five plants were randomly collected from each plot, and total inflorescence length and seed number were measured per plant.…”

“…Similarly, propyzamide (inhibitor of microtubule formation) also exhibits activity on established grass weeds [69] via root uptake, requiring higher levels of soil moisture as a result of low solubility [68]. The efficacy of propyzamide and haloxyfop-R + simazine treatments may be attributed to the considerable residual activity of propyzamide and simazine on later-emerging barley grass seedlings [24,68], with uptake facilitated by successive rainfall events. Residual control of later emerging seedlings may also help to explain the lower seed production observed in these treatments in contrast to both propaquizafop and fluazifop-P + butroxydim treatments, where later emerging seedlings set considerable seed.…”

Seed contamination in sheep: new investigations into an old problem

“…Despite almost 100 years of research, all of these species continue to cause carcass damage (Collins 2013 (Llewellyn et al 2016). Interestingly, certain populations of these grasses are spreading due to herbicide resistance (Owen et al 2015;Shergill et al 2015aShergill et al , 2016bShergill et al 2017a;Shergill et al 2017b) and variable seed dormancy patterns (Fleet and Gill 2012;Kleemann and Gill 2013) as a result of repeated herbicide exposure, changing farming practices (Fleet and Gill 2012;Recasens et al 2016) and potential adaptation to variable climatic conditions (Smith 1968;Gill and Blacklow 1985). Brome grass and barley grass now inhabits over 1.4 million hectares and 244,000 hectares, respectively (Llewellyn et al 2016).…”