Armyworms have long been a pest of rice, but 2015 was an outbreak year, and high populations have continued in subsequent years. We don't really know why this is happening, but it could relate to higher minimum winter temperatures (i.e. better winter survival), and/or migratory patterns from other western states and Canada. While there are products registered for armyworm management in rice, those products have their limitations, including loss of efficacy (pyrethroids) and label restrictions that limit when the product can be applied (carbaryl).

UC Cooperative Extension has responded to the problem by providing outreach on UC IPM guidelines for monitoring and treatment. We have also cooperated with the California Rice Commission on getting Section 18 emergency approvals of methoxyfenozide (Intrepid 2F), which has been approved for the 2020 season. (For more information, please see CA Rice News.) Research and extension efforts have been led by Luis Espino, Rice Advisor in Butte and Glenn counties. He has conducted product efficacy trials and initiated widespread monitoring in the Sacramento Valley. In cooperation with Luis, I have been monitoring populations in Delta rice.

Monitoring involves scouting for damage and deployment of pheromone bucket traps that catch true armyworm and western yellowstriped armyworm moths (Figure 1). Because small armyworms are hard to scout and large armyworms are hard to treat, we use trap counts and Growing Degree Day modelling (i.e. a temperature measure of time) to determine when the worms are “just right” to treat, knowing that armyworm larvae can grow to full size in three to four weeks. During the season, Luis writes a weekly blog to provide real-time information on trap counts to help growers and consultants with scouting and decision-making. Please consider subscribing to the blog.

I have been monitoring populations in the Delta since 2016. This year, I deployed the traps about a week earlier than I have in past years. The traps are already catching moths (Figure 2), so it will be important to begin scouting for feeding damage. I will provide periodic monitoring updates using this blog, but for weekly updates, please consider subscribing to Luis Espino's blog.

Figure 2. 2016-2020 Delta armyworm trap counts. The trap counts represent counts of true armyworm and western yellowstriped armyworm moths. The counts are average across three San Joaquin County fields.

Weeds are important pests of California rice systems, and weed management can account for roughly 17 percent of total operating costs, according to a UC cost of production study. Integrated weed management uses cultural and chemical practices and considers the following:

• Prevention (e.g. using certified seed, equipment sanitation, maintaining roads and levees)
• Cultural practices (e.g. land leveling, crop rotation, tillage, winter flooding, drill-seeding)
• Fertilizer placement and management
• Water management
• Monitoring
• Herbicides

Herbicides are important tools; however, resistance can occur when products are not rotated, or when diverse chemistries are not available.

In 2019, in cooperation with Corteva Agriscience, I conducted a trial to evaluate the efficacy of a new herbicide product called Loyant (florpyrauxifen-benzyl). Loyant is registered in rice growing states in the southern US but would be a new chemistry in California. Corteva Agriscience anticipates California rice registration in 2020, with the product being available for use in 2021. Previous trials have shown that Loyant provides good control of broadleaf weeds (e.g. ducksalad, redstems), smallflower umbrella sedge, and ricefield bulrush. It has some activity on Echinochloa species (e.g. barnyardgrass, watergrass). More data was needed, however, in drill-seeded systems. The objective of the trial was to assess the efficacy and crop tolerance of Loyant for weed control in drill-seeded rice in California.

The trial took place in the Delta region on a Kingile muck soil. This soil classification is characterized as having upwards of 40 percent organic matter in the top foot of soil. On high organic matter soils in the Delta, the typical practice is drill-seeding. Water-seeding, which is the typical practice in the Sacramento Valley, is not successful in the Delta because the soil particles can float and move too easily, causing seed to get buried too deeply and germinate poorly.

For a full report on this trial with methods and crop injury data tables, please see my website. Treatments are described in Table 1 below. We observed slight to noticeable leaf curling in the Loyant treatments at 14 days after treatment (DAT), but this had disappeared by 21 DAT. We observed no stunting or stand reduction with any of the treatments; nor did we observe any differences in heading. All treatments had similar weed control with the exception of the Prowl-only treatment, which had statistically higher weed counts. Loyant does not control sprangletop, so sprangletop was the weed most commonly observed. We found no differences in yield or seed moisture at harvest (Table 2 below), and we observed no lodging. Yield averaged 8965 pounds per acre across treatments, and seed moisture averaged 13.7 percent.

In summary, the purpose of this trial was to learn the efficacy and crop tolerance of Loyant (florpyrauxifen-benzyl) for weed control in drill-seeded rice. We observed slight leaf rolling with the Loyant treatments a couple weeks after treatment, but those symptoms were gone by the third week after treatment. We observed Loyant to have good activity on the Echinochloa species but not on sprangletop, which was expected based on previous company trials. We observed Loyant treatments to have similarly low weed counts compared to the grower standard practice, and no significant differences in yield among the treatments. Tank mixes will be needed to manage sprangletop. The results indicate that Loyant could be used in drill-seeded rice herbicide programs, providing a different chemistry for herbicide resistance management.

This information on products and practices is for educational purposes only and does not constitute an endorsement or recommendation by the University of California.

 

Table 1. Rice herbicide treatments.

Mark your calendar with these upcoming meetings brought to you by UC Cooperative Extension, USDA-NRCS, and the California Rice Experiment Station. See the links or attached flyer for more information.

 

1. UCCE Rice Production Workshop

Tuesday, August 7, 2018

8:30am - 3:00pm (lunch included with registration)

5311 Midway, Richvale, CA 95974

Registration is required. Visit http://ucanr.edu/rice2018 to register, or see this post for more information.)

 

2. USDA-NRCS Warm Season Cover Crops Field Day

Wednesday, August 22, 2018

10:00am-12:00pm

Lockeford Plant Materials Center, 21001 N. Elliott Rd., Lockeford, CA 95237

No registration required. See agenda in the attachment (below).

 

3. UC Davis Dry Bean Field Day

Thursday, August 23, 2018

10:00am-12:00pm

UC Davis Agronomy Farm: Take Hutchison Dr. approximately 1.5 miles west from Hwy 113, in Davis.  Turn south on Hopkins Lane, and then take the first left turn (heading east) onto a gravel/broken pavement road with a row of olive trees; park along the fence.  The field is located north of the Bee Biology Center. 

 

4. Rice Experiment Station Annual Field Day

Wednesday, August 29, 2018

7:30am-12pm (lunch included)

Rice Experiment Station, 955 Butte City Hwy, Biggs, CA 95917

No registration required. For more information, visit http://www.crrf.org/.

 

4. UCCE Alfalfa and Forage Field Day

Wednesday, September 19, 2018

7:30am-12:30pm (lunch included)

Kearney Agricultural Research and Extension Center, 9240 S. Riverbend Ave., Parlier, CA 93648

More information will be forthcoming.

UC Cooperative Extension will host a Rice Production Workshop on August 7, 2018 from 8:30am to 3:00pm at Lundberg Family Farms (5311 Midway, Richvale, CA 95974). The Rice Production Workshop is an in-depth workshop that covers the principles and practices of rice production. It is intended for those who are new to the rice industry or those who are looking to brush-up on their knowledge of the applied sciences of rice production. These workshops are generally hosted every two to three years. We ask for registration by August 1st, and the registration fee covers lunch, snacks, and a manual. Enrollment is limited to 75 people. We have applied for DPR and CCA continuing education credits. The agenda is below and in the attached flyer. Please contact your local farm advisor for more information.

Agenda:

8:30      Sign in, pick up class materials

9:00      Introduction and Workshop Overview

9:10      Rice Growth and Development

9:30      Land Formation, Water Management

9:50      Tillage, Planting and Stand Establishment

10:10    Break

10:30    Variety Selection

11:00    Invertebrates

11:30    Diseases

12:00    Lunch

1:00      Fertility

2:00      Weeds

3:00      Adjourn