In 2017, I started getting reports of a watergrass biotype/species (Echinochloa spp.) that was difficult to control using our suite of herbicides registered in rice. At the time, I knew we had multiple herbicide-resistance in late watergrass (Echinochloa phyllopogon), so I initially just thought the resistant biotype was spreading, and had maybe gained resistance to additional herbicide modes of action. However, once I started visiting fields, it quickly became apparent that this was not late watergrass (phenotypically-speaking). It also did not appear to be barnyardgrass (Echinochloa crus-galli), although the Echinochloa species are notoriously difficult to identify, and phenotypically quite variable in nature.

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).

Table 1. Preliminary distinguishing characteristics of watergrass species in California rice fields, based on seed characteristics. 

Preliminary Identification	Seed Description
Late watergrass	Large size, no awns
Early watergrass	Large size, awned (all seeds)
Barnyardgrass	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. 

University of California Cooperative Extension Sutter-Yuba-Colusa is holding a 3-hour pest management webinar on Wednesday, December 9^th, 2020 to provide pest management information and research updates on some of the major annual crops in the Sacramento Valley. The presentations are relevant to growers throughout California and are primarily focused on pest management of rice, field crops and processing tomatoes with a portion of the webinar devoted to updates on laws and regulation. 

The December 9th webinar will feature an hour of rice presentations given by Luis Espino, Rice Farming Systems Advisor in Butte County and Whitney Brim-DeForest, Rice and Wild Rice Advisor in Sutter-Yuba counties. Espino states, "This was a year with severe rice blast in the northern Sacramento Valley; the presentation will cover blast biology and management information. I will also review arthropod issues such as tadpole shrimp and armyworms.” Brim-DeForest says, “The webinar will cover the latest weed research in rice, including weedy rice, watergrass species, and the 2019 weed survey”.

Amber Vinchesi-Vahl, Vegetable Crops Advisor in Colusa and Sutter-Yuba counties, will provide information on pest management of processing tomatoes, the dominant vegetable crop in the Sacramento Valley. She states, "I will be providing information on important pest issues in commercial processing tomatoes and the latest research updates on disease and weed management."  

Sarah Light, Agronomy Advisor for Colusa and Sutter-Yuba counties will present information on area field crops. Light says, "My presentation will cover relevant pest management updates related to field crop production in the region." 

The webinar will also include a regulatory update for Sutter County by Scott Bowden, Deputy Agricultural Commissioner/Sealer. This portion of the program will include information on permitting and updates on chlorpyrifos and paraquat.

Enrollment is limited, so register early. The cost is $25 for the 3-hour webinar. For more details or to register, visit http://ucanr.edu/survey/survey.cfm?surveynumber=32431. DPR CE and CCA credits are pending (2 "other" hours and 0.5 Laws & Regs hours).  

If you have questions, contact Sarah Light at selight@ucanr.edu or call the UCCE Sutter-Yuba office at (530) 822-7515.

SUPPRESS® herbicide EC, a product manufactured by Westbridge Agricultural Products, was registered in California in 2015. Its active ingredients are Caprylic Acid and Capric Acid. It is registered for use in organic production, and it is labeled for use in “agricultural food and non-food crops”. In rice, it can be utilized only when the field is drained (no standing water allowed).

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.

Label: https://westbridge.com/products-pdf-documents/SUPPRESS_Herbicide_Label_161109.pdf

SDS: https://westbridge.com/products-pdf-documents/SUPPRESS_Herbicide_SDS_2015.pdf

For more information, contact UCCE Rice Advisor, Whitney Brim-DeForest (wbrimdeforest@ucanr.edu), and Roberta Firoved, Industry Affairs Manager for the California Rice Commission (rfiroved@calrice.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 [wbrimdeforest@ucanr.edu or call the UCCE Sutter-Yuba office at (530) 822-7515].