Article

Assessment of oxyfluorfen‐tolerant rice systems and implications for rice‐weed management in California 1

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Abstract

Background: Weeds are a significant barrier to rice production in California, exacerbated by lack of chemical control options and herbicide-resistance in persistent aquaphilic species. Oxyfluorfen-tolerant rice, created at the Rice Experiment Station (RES) in Biggs, California, was developed to provide an agronomic program for managing problematic grass and sedge rice-weeds including Oryza sativa f. spontanea Roshev. (weedy 'red' rice). Hand-pulling is the most common removal method for O. sativa spontanea because there are no herbicides registered for this pest in California. Oxyfluorfen was used in combination with oxyfluorfen-tolerant rice in 2019 and 2021 field studies to evaluate rice injury and weed control efficacy on prevalent rice-weed species. Additional studies were conducted in 2021 on University of California Davis campus to determine pre-emergent oxyfluorfen efficacy on four California O. sativa spontanea accessions. Results: Fields studies indicated minimal crop injury in the first 28 days after seeding (DAS), but no observable injury at 60 DAS in both years. Weed control with oxyfluorfen alone was 87% or greater for all weeds rated with the exception of Schoenoplectus mucronatus (L.) Palla (ricefield bulrush), and Leptochloa fascicularis (Lam.) A. Gray (bearded sprangletop) in both years. All O. sativa spontanea exposed to soil-applied oxyfluorfen successfully emerged through the soil surface, but became completely necrotic 28 days after flooding. Conclusion: Oxyfluorfen-tolerant rice system was demonstrated to be a viable management strategy for California rice growers who struggle with grass- and sedge-weed control as well as provide a novel herbicide option for California O. sativa spontanea management. © 2022 University of California, Davis. Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

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... Linuron is a broad-spectrum systemic herbicide that acts in the PRE and POSTemergence of weeds by inhibiting photosystem II (PSII), in the photochemical step of photosynthesis [17]. Regarding oxyfluorfen and flumiozaxin, both herbicides act by contact and control monocotyledonous and dicotyledonous weeds, with the mechanism of action being inhibition of the enzyme protoporphyrinogen oxidase (PPO) [18,19]. All these mo-lecules are very important for the control of G. parviflora at the early stages of development. ...
... This can help to reduce production costs and environmental impacts, and increase agronomic efficiency. The use of residual herbicides is a sustainable alternative, because it is performed at early stages of weed development (soon after germination), and the control is maintained for a longer time, reducing the need for sequential applications of herbicides, as well as preventing weeds from producing seeds that infest agricultural areas [18]. However, studies with such herbicides are still scarce, being of great importance for researchers and famers. ...
... Studies on the behavior of oxyfluorfen are still sparse in the scientific literature; however, as it is a herbicide positioned in PRE and is a PPO inhibitor, it is important to continue studies on this herbicide, as this mechanism of action is essential to avoid the development of resistant weed biotypes. Therefore, herbicides with PPO inhibitors tend to select weeds with resistance much more slowly than other herbicides [18]. ...
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This updated and much revised third edition of Seeds: Physiology of Development, Germination and Dormancy provides a thorough overview of seed biology and incorporates much of the progress that has been made during the past fifteen years. With an emphasis on placing information in the context of the seed, this new edition includes recent advances in the areas of molecular biology of development and germination, as well as fresh insights into dormancy, ecophysiology, desiccation tolerance, and longevity. Authored by preeminent authorities in the field, this book is an invaluable resource for researchers, teachers, and students interested in the diverse aspects of seed biology. © Springer Science+Business Media, LLC 2013. All rights are reserved.
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