- Author: Whitney B Brim-Deforest
This year brings several new chemical tools to California rice. With many herbicide resistant species as well as emerging problematic weed species, the new chemistries are a welcome tool for managing resistance and preventing the selection of resistant biotypes.
Last year, we had use of Loyant® CA Rinskor™ active (florpyrauxifen-benzyl) for the full season (registered late in 2022). Loyant®, which is an auxin mimic, is applied as a foliar product. It gives additional options for early-season control of sedges and broadleaf weeds, and although not strong on watergrasses when applied alone, provides added control when tank-mixed with other herbicides for grass control. Based on data collected in 2022-2023, two good tank-mix options for watergrass control are SuperWham®/Stam® (propanil) and Regiment (bispyribac-sodium). It does not control sprangletop.
Cliffhanger™ (benzobicyclon) was just registered in 2024, and is a new formulation of a previously-registered granular product already widely in use in California rice. Since it can be applied as a foliar product, it expands the timing that benzobicyclon can be applied in the flooded system. It can also be applied as a direct-stream application into the water. It is an HPPD-inhibitor, providing a good option for rotation. It controls sprangletop, ricefield bulrush and smallflower umbrella sedge. Additional tank-mix testing will be occurring this season to determine if it might be a good partner in combination with other herbicides for added late-season watergrass control.
The last product recently registered is Zembu™ (pyraclonil). Zembu™ is a granular formulation of pyraclonil, applied pre-emergence or at day-of-seeding into a flooded field. It provides control of smallflower umbrella sedge and broadleaf weeds, and provides suppression of watergrass. As a PPO-inhibitor, it is a new mode of action for watergrass, as the only other PPO-inhibitor registered in California rice only has activity on sedges. It will provide a great rotational option for growers at the beginning of the season, as well as a great partner product (for added control) with other granular into-the-water products.
As always, the label is the law, so make sure to read and follow the current labels for each of these herbicides (found on the manufacturers website or at the Department of Pesticide Regulation's website). Also check in locally with your Agricultural Commissioner's office for training information and any other county-specific requirements.
With these three new options, as well as the currently-registered products, rice growers in California should have a great suite of tools available this year, both for resistance management as well as to prevent the selection of future resistance. For help planning a weed management program, please reach out to your local Rice Farm Advisor.
Location: UCCE Sutter-Yuba Office; 142 Garden Hwy, Yuba City, CA 95991
RSVP: Click here to register
*Please RSVP by Wednesday, April 3, 2024 for an accurate lunch count. Thank you!
Contact: Whitney Brim-DeForest, 530-822-7515, wbrimdeforest@ucanr.edu
Propanil Stewardship Meeting Agenda
- Author: Ian Grettenberger
- Author: Kevin Goding
- Author: Sophie Allen
- Author: Luis Espino
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Rice seed midge damage was first officially recorded in California rice production in 1953, and this pest is actually a number of different species that are frequently lumped together in terms of defining them as a pest. Midges are some of the first colonizers of freshly flooded rice fields. In high enough numbers, they can cause economic damage to rice during establishment. They often are most problematic in late-planted rice fields or during cool springs when rice struggles to germinate and become established. They have been a spotty but challenging pest in recent years, so we have been working to examine management approaches. Current insecticide programs used for other early season pests like tadpole shrimp may not control rice seed midge.
- Author: Luis Espino
- Editor: Consuelo B Baez Vega
- Editor: Taiyu Guan
Stem rot is a common disease of rice that can cause blanking and lodging. When the disease is severe, the presence and effects of the disease on yield can be obvious. However, at lower levels, the symptoms and effects of the disease may “fly under the radar”.
Stem rot affects the tillers at the water level. Mid season, small black lesions appear on lower leaf sheaths. As the disease progresses, the pathogen penetrates the tiller and can reach the culm, causing rot. These symptoms are most obvious when fields are drained for harvest. Once plants start to senesce, it can be difficult to identify stem rot symptoms because plants dry out.
The severity of stem rot is determined at drain time using a ranking that goes from 0 (no disease) to 4 (tillers rotted through). Several years of trials have shown that for each increase in severity level, there is a 3.2% yield loss. The table below shows the yield losses that can be expected under each severity level for three different yield potentials.
- 50% of tillers show stem rot symptoms = Severity level 1
- 100% of tillers show stem rot symptoms = Severity level 2 or higher
Yield losses at severity level 2 could be significant, so a manager should aim to be below this disease level. To determine incidence at drain time, cut a handful of tillers at the soil level and determine how many show symptoms of stem rot. Do this at several representative places in the field, avoiding nitrogen overlaps or skips, until you feel you have a good estimate.
The second challenge is that evaluating the severity of stem rot at drain time provides information that cannot be used to make any management actions the current year. However, the information can be used to plan management for the following year. Because stem rot inoculum survives in crop residue in the soil, disease severity levels tend to be uniform across years.
To manage stem rot, an integrated approach is needed. Managing straw after harvest is key. Burning or decomposing straw aids in reducing the amount of inoculum that survives from year to year. Excess nitrogen and potassium deficiency can significantly increase the severity of the disease. While there are no resistant varieties, very early varieties (CM-101, M-105) tend to develop more severe stem rot that varieties with longer cycles (M-209, M-211). Finally, fungicides can help manage the disease. Azoxystrobin applied at the early heading stage has been shown to reduce the severity of the disease by 30%.
Survey: Challenges and Opportunities for Organic Rice
In the next few weeks, you will receive an email with a link to a survey being conducted as part of a project looking at the attitudes of rice producers towards organic farming. This project is trying to understand what drives US rice producers to adopt organic farming and what factors limit adoption, and is a collaboration between University of Arkansas, Texas A&M University, and University of California Cooperative Extension. The information generated by the project can help the industry identify adoption barriers and try to address them through policy and extension, so that organic production can become a viable option for more producers. The survey should take 15-20 minutes to complete. You can learn more about this project at The Organic Center website (https://organic-center.org/site/challenges-and-opportunities-us-organic-rice)
- Author: Bruce A Linquist
- Author: Luis Espino
- Author: Whitney B Brim-Deforest
- Author: Michelle Leinfelder-Miles
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Every year, the University of California Cooperative Extension, in cooperation with the Rice Experiment Station (RES), conducts rice variety trials in several locations of the Sacramento Valley (fig. 1). The trials are conducted at the RES and eight farm locations across the Sacramento Valley, and one location in the San Joaquin Delta (not on the map) representing the main production areas of California. In 2023, the South Yolo trial was not conducted. Plots in the Sacramento Valley trials were 200 ft2 and hand seeded while in the San Joaquin Delta trial plots were 150 ft2 and drill seeded; seeding rate for all trials was of 150 lbs/a. Grower cooperators treated the trial in the same manner as the rest of the field. Parameters evaluated in the trials included seedling vigor, days to 50% heading, plant height, lodging at harvest, grain moisture at harvest, and grain yield at 14% moisture. Varieties are replicated four times. In this summary, only yields are presented. All other parameters are included in the complete report, which will be available on our website at the end of February (http://rice.ucanr.edu).