- (Public Value) UCANR: Safeguarding abundant and healthy food for all Californians
- Author: Bruce A Linquist
In most years, farmers manage their winter straw by flooding a field where the rice straw has either been chopped or chopped and incorporated. In these cases, the flood water helps to ensure good decomposition. This year however, is different. Many growers are faced with the fact that they will have no water to flood their fields over the winter. Good straw decomposition is important as it will impact nitrogen management decisions the following year. It may also affect the survival of stem rot and aggregate sheath spot sclerotia, the fungus resting structures, in the soil. Too much straw will tie up nitrogen fertilizer early in the season and will also serve as a host for stem rot and aggregate sheath spot. So, what are the options besides burning?
First, removing straw is an option. Driving around, I have seen a lot of straw bailing going on. Bailing rice straw removes about half of the rice straw. This is a good start, but it would still be nice to make sure the rest of it gets decomposed by following the suggestions in the second option.
The second option is to do the best possible to make sure rice straw decomposes without winter flooding. Simply chopping the rice straw and leaving it on the surface will likely not do the trick – especially if there is not much rain over the winter. It is really important to make sure there is good soil-water-straw contact to ensure good decomposition. For this to occur you need to incorporate your rice straw. Studies were conducted here in California in the late 1990s which compared burning, bailing, incorporation and rolling of rice straw. They found that incorporating rice straw resulted in the greatest amount of straw decomposition and the least straw remaining the following spring. This result was seen in both fields that were flooded and those that were not. When the fields are not flooded, rainfall can provide water for good decomposition.
Date: August 3, 2021
Location: UCCE Sutter-Yuba Office
142A Garden Highway, Yuba City
Free (lunch provided)
9:00–9:30 am Research Updates 2020-2021 (Whitney Brim-DeForest, CE Rice Advisor)
9:30–10:00 am Weedy Rice Survey 2020 (Luis Espino, CE Rice Advisor)
10:00-10:15 am Weedy Rice Identification (Luis Espino, Whitney Brim-DeForest, CE Rice Advisors)
10:15–10:30 am —BREAK— (plants to view)
10:30–10:45 am Non-conventional Path to Pesticide Registration (Roberta Firoved, California Rice Commission)
10:45-11:00 am Preventing Spread of Weedy Rice with Certified Seed (Timothy Blank, California Crop Improvement Association)
11:00-11:15 am Weedy rice emergence under various environmental conditions (Liberty Galvin, PhD Candidate, UC Davis)
11:15 am —LUNCH—
This project is sponsored with funding from the California Rice Commission.
**CE credits (CCA, DPR) pending**
We came up with a preliminary set of characteristics to distinguish this unknown biotype or species (we are unsure if it is a distinct species) from the typical barnyardgrass and late watergrass found in California rice fields. All were characterized by their seed size and awns (Table 1).
Large size, no awns
Large size, awned (all seeds)
Small size, variably awned (some seeds have awns, some do not)
New biotype/species (unknown)
Small size, awned (all seeds)
In 2018, we collected 8 samples from the field, and used two late watergrass samples from known susceptible populations to use as controls. We conducted a screening in the greenhouse, to see if we could replicate what we were seeing in the field. Field rates of Cerano® (clomazone), Butte® (benzobicyclon+halosulfuron), Granite GR® (penoxsulam), and Bolero® (thiobencarb) were used as the early-season granular applications. Field rates of SuperWham® (propanil), Regiment® (bispyribac-sodium) and Clincher® (cyhalofop) were used to test for the late-season cleanup applications. In the greenhouse, all applications were made at the 1.5 leaf stage of the grass.
Results indicate that 8 of the 8 samples were not controlled (less than 50% by biomass, in comparison to the untreated controls) by Granite GR® or Butte®. 7 of the 8 samples were not controlled by Bolero®, and 6 of the 8 were not controlled by Cerano®. This closely follows what growers were stating had occurred in the field: the watergrass was escaping early-season control, and was then difficult or impossible to control with later-season herbicide applications. SuperWham®, Regiment®, and Clincher® controlled 8 of 8 samples (at least 60% control). However, since the greenhouse application was conducted at an early timing (1.5 leaf stage), it is possible that later applications in the field may be less effective.
For growers, the implications of this preliminary screening are that control of this new biotype/species will need to be prioritized early in the season. Possible treatments (keep in mind that these have not been field-tested and could cause phytotoxicity) could be: a stale seedbed using a non-selective herbicide; pre-plant Abolish® (thiobencarb) followed by Cerano® or Butte® or Granite GR®; Cerano® followed by Butte® or Bolero® or Granite GR®; or Butte® followed by Granite GR® or Bolero®. There is still a strong likelihood that a follow-up application may still be required later in the season, even with these early-season applications.
In 2020, more than 60 watergrass samples were collected from all over the rice-growing region. We will continue working on identification and conduct further herbicide screening this year.
- Author: Whitney Brim-DeForest
- Author: Roberta Firoved
Since 2019, UCCE Rice Advisor Whitney Brim-DeForest has been testing SUPPRESS® herbicide for use in weed control in rice. In 2019, she collaborated with Jim Cook (Colusa County Farm Supply), to spot spray weedy rice in a field containing Type 3 (long awns, straw hulled). The application was made with a handheld backpack sprayer, at the highest labeled rate. The timing was too close to heading, however, and some of the weedy rice plants recovered.
This past season, in 2020, we did further testing in the field, on several different weedy rice types (field was a mix of Types 1, 2, 3, and 5). The application timing for the field testing in 2020 was made with a handheld backpack sprayer, at the highest labeled rate. The timing was approximately at panicle initiation, and at two weeks after application, the weedy rice plants were 100% controlled. At harvest, there was some regrowth, but none of the plants produced viable panicles.
For use in weedy rice spot spraying in 2021, SUPPRESS® could be an option, but the label does not allow for application when there is standing water in the field. Therefore, in order to be used, the field will need to be drained before application. Application timing is after the last grass herbicide has been applied, but before the weedy rice has started to flower (generally no earlier than 60 days after seeding). Reflooding is recommended within 48 hours of application to reduce the germination of additional weeds, unless the field can remain drained until harvest.
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.
For more information, contact UCCE Rice Advisor, Whitney Brim-DeForest (email@example.com), and Roberta Firoved, Industry Affairs Manager for the California Rice Commission (firstname.lastname@example.org)
University of California Cooperative Extension Sutter-Yuba-Colusa is holding a series of webinars in September and October to provide research updates on some of the major crops in the Sacramento Valley. The classes are relevant to growers throughout California and are primarily focused on pest management and pesticide safety.
The September 9th webinar will feature Franz Niederholzer, Orchard Systems Advisor. "We will be reviewing proven almond IPM practices with an eye to reducing input costs, where possible, while delivering effective pest control," says Niederholzer. He has been working in almonds in the Sacramento Valley for almost 20 years.
Amber Vinchesi-Vahl, Vegetable Crops Advisor, will give her webinar on September 16th. She states, "I will be providing information on important pest issues in vegetables and the latest research updates on disease and weed management in processing tomatoes and cucumber beetles in melons." Her research on tomatoes covers cultivator trials for within-row weed control and monitoring of soilborne fungal pathogens.
Whitney Brim-DeForest, Rice and Wild Rice Advisor, will present September 30th. "The webinar will provide an opportunity for discussion and interaction about weed identification," she says. "We will also cover the latest research updates on specific weed species, resistance management, and new herbicides in rice." The information is relevant to both organic and conventional rice growers, so all are encouraged to attend.
The final webinar will take place on October 7, and will be given by Sarah Light, Agronomy Advisor. Light says, "We will cover opportunities to decrease environmental risk through pesticide selection and application, accurate diagnosis, and reduction of loss to the environment."
Enrollment is limited, so register early. The cost is $20 for 1, $35 for 2, $50 for 3, and $60 for 4 webinars. For more details or to register, visit http://ucanr.edu/syc-uccevirtualwebinars. DPR CE credits have been approved (4 "other" hours total, 1 per class), and CCA credits have been approved for IPM credits (4 hours total, 1 per class).
If you have questions, contact Whitney Brim-DeForest [email@example.com or call the UCCE Sutter-Yuba office at (530) 822-7515].