- Posted by: Gale Perez
Sterile Pollen Technique Shows Promise for Palmer Amaranth Weed Control
Newly published research provides a novel and sustainable weed-management strategy
WESTMINSTER, Colorado – 22 May2024 – Recently published research in the journal Weed Science shows that a sterilization technique commonly used to control insect pests can be modified to control weeds that require pollination to reproduce. More specifically, the researchers determined that employing a sterile pollen technique (SPT) could effectively disrupt Palmer amaranth (Amaranthus palmeri S.) reproduction.
Palmer amaranth remains among the most detrimental weeds in North American agriculture, and its resistance to several herbicide groups makes its control a serious challenge. Yet, researchers in this study were able to find a promising new control method for Palmer amaranth and possibly for many other difficult-to-control weeds.
“Our results indicate that SPT, using irradiated pollen, can be a valuable approach for reducing weed-seed production,” says Mohsen B. Mesgaran, Ph.D., a plant sciences assistant professor at the University of California Davis, and the article's corresponding author. “SPT also holds potential for broad-spectrum weed control by mixing sterile pollen from multiple weed species in a single application.”
Additionally, the researchers found that SPT shows promise for managing troublesome herbicide-resistant weeds that have survived in-season control efforts.“We observed the greatest reduction in seed set when irradiated pollen was introduced to the stigma through artificial pollination prior to open pollination,” notes Mesgaran. “It appears that irradiated pollen exerts a preventive effect on naturally occurring pollen that arrives later.”
While the researchers determined that a dose of 300 units of ionizing radiation (Gy) strikes the optimal balance to achieve both efficient Palmer amaranth pollination and seed sterility, challenges still remain. For example, irradiated pollen is currently less competitive than naturally occurring pollen. Thus, field managers may need to employ additional measures to successfully control Palmer amaranth with SPT, such as dispersing irradiated pollen in the field before male anthesis and releasing it multiple times.
More information about SPT and Palmer amaranth control can be found in the article (by Wenzhuo Wu and Mohsen B. Mesgaran), “Exploring sterile pollen technique as a novel tool for management of Palmer amaranth (Amaranthus palmeri).” The research is featured in Volume 72, Issue 3 of Weed Science, a Weed Science Society of America journal, published online by Cambridge University Press.
Original source: Weed Science Society of America (https://wssa.net/2024/05/sterile-pollen-technique-shows-promise-for-palmer-amaranth-weed-control/)
/h3>- Posted by: Gale Perez
From the eOrganic and Performance and Economics of Electric Weed Control in Organic Perennial Crops Project:
Electric Weeding Research Updates
(Click HERE to see the presentations)
- Electric Weed Control in Orchards • Tong Zhen, Ph.D. student (Hanson Lab) at UC Davis
- Crop Safety and Weed Control in Organic Highbush Blueberries Using Electric Weeding • Luisa Baccin, Ph.D. student (Moretti Lab) at Oregon State University
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- Posted by: Gale Perez
Congratulations to UC Davis weed science graduate student Erika Escalona (Fennimore Lab) for winning 1st place in the student poster presentation category at the 2024 California Plant and Soil Conference on Feb. 6-7, 2024 in Fresno, CA.
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Evaluating Bacterial Diversity in Steam Fumigation Treatments in the Salinas Valley's Lettuce Fields
Erika Escalona, University of California, Davis; Steve Fennimore, UC Cooperative Extension, Weed Specialist, Salinas; Department of Plant Sciences, University of California, Davis; J.S. Rachuy, Department of Plant Sciences, UC Davis; Cristina Lazcano, Department of Land, Air and Water Resources, UC Davis
As the specter of climate change looms larger, sustainable and environmentally friendly alternatives for pest and pathogen control in agriculture are becoming increasingly imperative. Steam fumigation, once an antiquated method overshadowed by chemical pesticides, is experiencing a resurgence due to heightened environmental concerns. Despite its historical use, there has been limited exploration of scaling up steam fumigation for field applications in vegetable crops. Although existing studies have highlighted the efficacy of steam fumigation, a critical knowledge gap persists regarding its impact on the soil microbiome, a fundamental determinant of agricultural productivity. This study seeks to advance the validation of steam fumigation as a practical alternative to chemical fumigation by conducting a comprehensive assessment of vegetable productivity in lettuce and spinach grown in steamed soils versus non-steamed soils. The experiment utilized a custom-built steam applicator equipped with a low-pressure 1,000 kg/hour steam generator in Salinas, CA. All research and trials were conducted at the Salinas Extension and USDA Center. Soil samples were collected before and after steam application, and crops were meticulously monitored for disease and weed control, alongside yields at harvest. Preliminary results indicate effective weed control and increased yields in the presence of disease pressure. In addition to evaluating the efficiency of steam fumigation in weed and pathogen control, this study delves into a thorough investigation of the bacterial diversity of soils. The trials, conducted from July 2023 to August 2023, involved verifying the performance of the steam applicator, assessing beneficial soil organisms using 16S sequencing, and evaluating treatment impact on bacterial diversity. By examining the results obtained from these multifaceted trials, we aim to provide comprehensive insights into the overall effectiveness of steam fumigation and its potential application in sustainable agriculture practices, with a specific focus on its influence on the soil microbiome.
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To view the full story, visit UC Davis Plant Sciences Dept. News, Feb. 22, 2024.
Contacts
- Erika Escalona: eescalona@ucdavis.edu
- Steve Fennimore: safennimore@ucdavis.edu
Escalona-Erika24'UCANRconference
- Author: Whitney B Brim-Deforest
- Author: Roberta Firoved
- Posted by: Gale Perez
Dates for the training are posted on the California Rice Commission calendar https://calricenews.org/events/, as well as the UC Rice website.
Controlled weeds are sprangletop, ricefield bulrush, and smallflower umbrella sedge. The application timing begins from day of seeding up to 82 days before harvest. Recommended timing for sedges is pre-emergent up to the 5-leaf stage, and for sprangletop, pre-emergent up to the 2.5 leaf stage as well as at tillering.
Flood water should be a minimum of 4 inches when the product is applied. The active ingredient, benzobicyclon, is a proherbicide, meaning that it is not active until it comes into contact with water. Therefore, for maximum efficacy, water should be held in the field for at least 5 days. Longer periods of flooding will result in better efficacy, whereas a drain soon after application will both reduce efficacy as well as encourage a new flush of weeds. The recommended waterhold is 10-14 days for maximum efficacy.
Cliffhanger™ should only be applied once per season. It is not recommended that it be applied in the same season as any other HPPD-inhibitor product (Butte®). Applying both in the same season can select for herbicide resistance and may cause significant phytotoxicity to the rice. Repeated applications, both during the same season, or season after season, can select for resistance, particularly in sprangletop, ricefield bulrush, and smallflower umbrella sedge.
Remember to always follow all label instructions when applying any pesticide, as the label is the law. Make sure to pay particular attention to the Use Precautions and Restrictions. Consult your local Agricultural Commissioner's Office regarding buffer zones and aerial restrictions, before making any applications.
Label and SDS: https://www.gowanco.com/products/cliffhanger-sc-herbicide
Original source: Rice Notes - January 2024 newsletter
- Author: Aaron Becerra-Alvarez
- Author: Sarah Lorraine Marsh
- Author: Kassim Al-Khatib
- Posted by: Gale Perez
A new herbicide for early-season weed control in water-seeded rice will be available soon. The herbicide active ingredient (a.i.) is pyraclonil, which will be trademarked as Zembu™ (1.8% a.i.) by Nichino, America Inc. The mode of action is a protox porphyrinogen (PPO)-inhibitor or Group 14. This herbicide is formulated as a granule and will be used as a residual preemergence for application on the day of seeding onto flooded fields. The use rate is 14.9 lbs ac-1 applied by air. While this herbicide is not a new mode of action for water-seeded rice, it is a new mode of action for early-season residual weed control. Pyraclonil is widely used for weed control in paddy fields worldwide and is the most commonly utilized herbicide in Japan [1]; however, Zembu™ will be the debut of pyraclonil to the U.S. rice market [2].
In order to evaluate Zembu's strengths and weaknesses, UC researchers, in collaboration with Nichino, America, has conducted extensive research on Zembu since 2015 and developed foundational information for the use of Zembu in California water-seeded rice. In this post we highlight two studies which demonstrate Zembu's use and how it can be incorporated in an herbicide program for season-long weed control.
Zembu Timing
In the study conducted at the Rice Experiment Station in Biggs, CA in 2019, 2020 and 2023, Zembu application timings were evaluated. The pre-seed bare ground was the first Zembu application at 3 days before flooding the field and seeding rice, then the application at 1-inch flood, then the application at 4-inch flood, followed by the application 3 days after flooding (DAF). The rice was seeded after the 1-inch flood and before the 4-inch flood. 'M-209' rice was seeded in 2019 and 2020 at 120 lbs ac-1 and 'M-209' was seeded in 2023 at 150 lbs ac-1. The objective of studying the different application timings was to determine if the application timing will affect weed control and rice response.
Cross species weed control was not affected by the different application timings of Zembu (Table 1). Zembu does not have great activity on ricefield bulrush and changing the application timing did not improve its control, which reached only 60% by 42 days after treatment (DAT) (Table 1). Zembu provided excellent control of smallflower umbrella sedge and all present broadleaves, which included ducksalad, water hyssop and redstem (Table 1). Across years, there were differences in control levels for watergrass control; however, there were no observed differences in watergrass control across the application timings (Table 2). In 2020, where watergrass control levels were low, was a year when the whole field had an increased pressure of watergrass caused by late rains immediately before the field preparation and initial flood, which provided soil moisture to give the grasses a head start. In 2019 and 2023, all weeds and rice germinations were initiated at time of flooding and led to greater control of watergrass (Table 2). The Zembu label will note that watergrass is suppressed by the chemical, not controlled. When applicators use Zembu for herbicide control, the incorporation of other herbicides to control ricefield bulrush and watergrass populations will be important.
Zembu in Herbicide Programs
Zembu will need to be incorporated into herbicide programs for season-long control. In the study conducted in 2019 and 2021 at the Rice Experiment Station in Biggs, CA, herbicide programs that included Zembu were evaluated for weed control and rice response. ‘M-206' rice was seeded at 120 lbs ac-1 and 150 lbs ac-1 in 2019 and 2021, respectively. All Zembu applications were done at day of seeding (DOS) onto the 4-inch flood. All other herbicides were applied following their label (Table 3).
When accompanied and followed by other herbicides, Zembu is a great addition to achieve season-long weed control (Table 3). In this study, it is observed that Zembu alone did not control the watergrass and when followed by various other herbicides the control level was increased (Table 3). Similar with ricefield bulrush control, other herbicide combinations increased the control levels when compared to Zembu applied alone (Table 3).
Rice response was minimal across treatments except with the Zembu and Bolero Ultramax combinations, which demonstrated greater visual injury early on. However, injury was overcome later in the season and rice grain yield did not differ across treatments (Figure 1).
Zembu will be a great addition to the herbicides available for early-season weed control in water-seeded rice.
References
[1]. Zhang YB (2014) Development and application of pyraclonil in paddy field. World Pestic 36(6):1-3
[2]. Anonymous (2023) Zembu™ Herbicide. Nichino America, Inc. Accessed on January 14, 2024 from https://nichino.net/products/zembu-herbicide/
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