Emergence and early growth of multiple herbicide–resistant and -susceptible late watergrass (Echinochloa phyllopogon)

Abstract

Late watergrass is a competitive weed of rice that is well-adapted to both aerobic and anaerobic environments. Cultural controls such as a stale-seedbed and alternating from wet- to dry-seeding have been proposed as management options. However, the effects of these systems on its emergence and early growth are unknown. The objective of this study was to modify a previously-developed population-based threshold model (PBTM) to predict emergence and early growth under field conditions. In 2013, a series of experiments were conducted at the California Rice Experiment Station (CRES) in Biggs, CA to evaluate emergence and early growth of multiple-herbicide resistant and susceptible late watergrass at four burial depths (0.5, 2, 4, and 6 cm) under three irrigation regimes: Continuously Flooded (CF), Daily Flush (DF) and Intermittent Flush (IF). Resistant plants emerged at a significantly higher rate under the IF treatment (p < 0.05). Both biotypes showed decreasing emergence with increasing depth, and no plants emerged from the 4 or 6 cm depths in the CF treatment. Using the Gompertz growth curve, resistant plants had greater predicted growth rates (k), lower predicted maximum heights (h max ), and a shorter time to predicted maximum growth rate (t m ) than susceptible plants under the CF and DF treatments. Under the IF treatment, the susceptible plants had greater k, lower h max and shorter time to predicted t m . Information about burial depth and irrigation was incorporated into a previously-developed PBTM for late watergrass, and validated at the CRES in a field with a susceptible late watergrass population in 2013 and 2014, under two irrigation systems, CF and IF. Model fit was best in the CF treatments (average AIC = 199.05) compared to the IF treatments (average AIC = 208.6).

Echinochloa in mid-southern U.S. and California rice: What is known and what are the knowledge gaps?

“…The use of alternate dry and wet seeding has the potential to disrupt the ecological cycle and, as a result, restrict the proliferation of Echinochloa species in the rice cropping system since these species have a niche that is ecologically distinct in terms of moisture regimes. Because frequent drought has increased concerns about water management in California rice, there may be an increase in the number of farmers who practice dry seeding instead of the traditional continuously flooded system (Brim-DeForest et al 2022). Studies on the impact of dry seeding on weed dynamics, its ecological fitness, or its role in managing herbicide resistance have received some attention in recent years (Brim-Deforest et al 2017b, 2022; Ceseski et al 2022; Pittelkow et al 2012).…”

“…Because frequent drought has increased concerns about water management in California rice, there may be an increase in the number of farmers who practice dry seeding instead of the traditional continuously flooded system (Brim-DeForest et al 2022). Studies on the impact of dry seeding on weed dynamics, its ecological fitness, or its role in managing herbicide resistance have received some attention in recent years (Brim-Deforest et al 2017b, 2022; Ceseski et al 2022; Pittelkow et al 2012). Brim-DeForest et al (2017a) evaluated weed community dynamics under various water management regimes in California rice and found a greater abundance of Echinochloa species occurred in a dry-seeded alternate wet and dry water management regime compared to continuously flooded conditions.…”

“…Accurate prediction of barnyardgrass emergence, however, will require experiments that adequately control the sources of such variations (Bagavathiannan et al 2011). In California, late watergrass populations emerge in a biphasic pattern, and the ability to model the second phase of the biphasic emergence curve is necessary (Brim-DeForest et al 2022).…”

Control of Echinochloa spp. and Leptochloa fascicularis with the novel dihydroorotate dehydrogenase inhibitor herbicide tetflupyrolimet in California water-seeded rice

“…Due to limited residual activity of these products and a narrow weed control spectrum, common weed control strategies include the application of multiple herbicides to achieve effective control of grass, sedge, and broadleaf weeds in rice fields. The reliance on limited herbicidal chemistries for decades in continuous rice has selected for weed populations that are resistant to these herbicides (Becerra-Alvarez et al https://doi.org/10.1017/wet.2024.21 Published online by Cambridge University Press 2022; Brim-DeForest et al 2022). Multiple cases of herbicide resistance have been detected in all aforementioned grass and sedge weed species and redstem, to various active ingredients throughout California rice fields (Fischer et al 2000;Yasuor et al 2008Yasuor et al , 2009Abdallah et al 2014;Hanson et al 2014;Heap 2014;Valverde et al 2014;Becerra-Alvarez et al 2023).…”