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 2021 season. (For more information, please contact your county Agricultural Commissioner's office.)
In cooperation with Luis Espino, Rice Advisor in Butte and Glenn counties, I have been monitoring armyworm populations in Delta rice since 2016. Monitoring involves scouting for damage and deployment of pheromone bucket traps that catch the moths. As of the week of June 14th, trap catches in the Delta are still low – about two moths per day – but there is some variation across locations, with lower Roberts Island having higher catches than Wright-Elmwood Tract and Staten Island. Over the years, the peak trap catches have occurred from the middle of June to early July (Figure 1), so now is the time to ramp up monitoring.
In previous years, we have trapped for both true armyworms and western yellowstriped armyworms. It appears, however, that the true armyworms are the ones that damage rice, so this year, we have focused our trapping on them. There are three locations in the Delta, and at each location, there are three traps that span adjacent fields. Therefore, we're able to monitor population variation within locations and across locations.
Armyworm larvae can grow to full size in three to four weeks. 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. (Pardon the Goldilocks reference!) 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. This year, he is also using an interactive mapping tool called Ag Pest Monitoring, which you can use to view counts in real-time and across trapping locations. Please consider subscribing to Luis Espino's blog.
Figure 1. 2016-2021 Delta armyworm trap counts. The trap counts represent the number of moths caught per day, averaged across three Delta locations. The 2021 counts are still low, averaging just two moths per day during the week June 14th, but now is the time to intensify monitoring since peak populations tend to occur between now and early July.
Last summer, I reached out to those of you on my email and blog subscriptions about an online survey that UCCE was conducting. The purpose of the survey was to receive your input on the most important issues in agronomic crops production. We hoped to learn how UCCE could best address those issues through research and outreach. The survey was sent over email and open for responses for about a month and a half. It was sent to growers, consultants (i.e. PCAs, CCAs), and allied industry professionals statewide. In the end, we received 483 responses, of which 89 were from San Joaquin County, and 63 were from Sacramento County. San Joaquin County had the highest number of respondents among counties – followed by Fresno, Colusa, and Kern counties – so many thanks to those of you who were able to fill out the survey. In San Joaquin County, 19 respondents were growers, 29 were consultants, and the rest described themselves as allied industry. In Sacramento County, 10 respondents were growers, 12 were consultants, and the rest were from allied industry. Respondents received slightly different questions depending on their job category.
We asked growers to estimate, in a given year, what percentage of the land they farmed was in field crops, vegetable crops, and trees and vines. In San Joaquin County, the average response was 45 percent in field crops, 10 percent in vegetables, 39 percent in trees and vines, and 7 percent in an “other” category, like pasture or nursery crops. In Sacramento County, the responses averaged 70 percent in field crops, 4 percent in vegetables, 24 percent in trees and vines, and 2 percent in “other.” Among consultants in both counties, their average time consulting was 39 percent in field crops, 8 percent in vegetables, 49 percent in trees and vines, and 4 percent in “other.”
Combining the data for both counties, grower respondents indicated that of their total farmed acreage, roughly 84% is irrigated and 58% is owned versus leased. Growers identified their top acreage field crops over the last three years as alfalfa, dry beans, grain corn, silage corn, small grains forage hay, and wheat. For those crops, growers identified top production challenges and primary reasons for growing them (Table 1). Additionally, growers identified factors affecting their management decisions. Some of the issues that were identified as “always” or “often” affecting management decisions, and the percent of growers responding with that issue were as follows: crop yield (100%), profitability (96%), crop quality (92%), certainty that a management practice will work (88%), soil fertility (84%), availability of water (81%), ease of implementation (81%), and land stewardship (77%).
Table 1. Highest priority management challenges and primary reasons for growing the top acreage agronomic crops identified by San Joaquin and Sacramento County growers. The top challenges and top reasons are followed by the percent of growers who identified the categories.
We also asked respondents about how they engage with UCCE and how they prefer to receive information. The percent of all respondents from the two counties who answered “very valuable” to the following services were as follows: crop diagnosis (77%), continuing education credits at meetings (72%), on-farm trials (71%), and on-farm consultations (52%). The percent of respondents engaging with UCCE at least 1-2 times per year were as follows: read a newsletter (95%), attended a field day (89%), read a blog (88%), called a farm advisor for a farm call (66%), engaged over social media (41%). The type of information that respondents want to receive from UCCE include on-farm trial results, cost of production information, and decision support tools, among others. In terms of how respondents prefer to receive information from UCCE, there was overwhelming interest in the following methods: websites, in-person meetings (i.e. field days, grower meetings), newsletters, and fact sheets. These methods were supported regardless of how the respondents categorized their vocation (i.e. grower, consultant, or allied industry).
In addition to learning from you what are the challenges in agronomic crops production, we were also interested in learning how we could respond to those challenges with research and extension. Table 2 illustrates how respondents (all vocations combined) prioritize agronomic crops production topics for UCCE research and extension programming. What was enlightening, albeit a bit sobering, were the responses to the open-ended question, “Do you have ideas for applied research or extension that you would like to see tested?” Example responses included how to manage limited water on alfalfa, how to improve leaf retention during alfalfa harvest, how to use liquid manure in subsurface drip irrigation systems, research on soil amendments for modifying pH and micronutrients, salinity and leaching, how to build soil organic matter, more variety evaluations, pest management studies particularly in alfalfa and dry beans, and research on Delta rice production, among others. It is a sobering list because it illustrates the numerous and complex needs for research and outreach. We will use these results to direct our programming and to advocate for the hiring of more farm advisors to work on these topics. We recognize that a limitation in our survey method was that we targeted people who are already connected with UCCE. We will continue to work on extending our offerings to those who are not yet connected with us.
In summary, I want to thank everyone who was able to participate in this survey. Your feedback is valuable, and we will use it to shape local and statewide UCCE programming in agronomic crops. Of course, your feedback is always appreciated, regardless of whether there is a survey circulating or not! Please never hesitate to reach out to me with comments, questions, or observations from the field.
The UC Davis Small Grains and Alfalfa Field Day will take place virtually in 2021. The meeting will be held on Wednesday, May 12, 2021 from 1:00 to 4:30pm. The agenda is below, and continuing education credits will be offered. To receive credits, you must register for the event. There is NO registration fee. Please see this website for registration and meeting login information. We hope to have you join us!
1:00 Welcome and opening remarks: John Palmer Executive Director, CCIA
1:05-2:45 UC small grain breeding, variety evaluations, agronomic research and extension
1:05 Update from the California Wheat Commission: Claudia Carter, Executive Director California Wheat Commission
1:10 UC Wheat Breeding Update: Jorge Dubcovsky and Oswaldo Chicaiza, UC Davis
1:18 UC Malting Barley & Oat Breeding Update: Alicia del Blanco, UC Davis
1:24 Breeding Triticales for Bread and Forage: Josh Hegarty, UC Davis
1:30 Evaluating Small Grain Varieties for Grain Yield, Grain Quality, Stress Stability, Pest Resistance, and Biomass Productivity Potential: Mark Lundy, UC Davis/UCCE
1:45 Interactive Web Tools for California Small Grain Management: Soil nitrate quick test; California weather; Nitrogen Fertilizer Management Tool; Seeding rate calculator: Taylor Nelsen and Mark Lundy, UC Davis/UCCE
2:00 Case Study: Using N-rich Reference Zones to Guide N Fertilizer Management for Irrigated Triticale in the San Joaquin Valley: Nicholas Clark, UCCE
2:20 Above and Belowground Productivity of Perennial Wheatgrass (Kernza) Compared to Tilled and No-till Annual Wheat: Kalyn Diederich, UC Davis
2:30 Evaluating Biosolid Fertilizers in Sacramento Valley Small Grain Crops: Konrad Mathesius, UC Cooperative Extension
2:45 – 4:30 UC Alfalfa & Forage Virtual Field Day
2:45 Weed Control During Stand Establishment: Sarah Light, UCCE Advisor, Sutter/Yuba Counties
2:57 Update on Weed Control Field Studies in the Intermountain Area: Tom Getts, UCCE Advisor, Shasta County
3:09 Importance of Resistance Management in Alfalfa: Ian Grettenberger, Madi Hendrick, UC Davis
3:21 Use of Drones for Insect Management: Rachael Long, UCCE Advisor, Yolo/Solano/Sacramento
3:33 Updated on Blue Alfalfa Aphid and Control in California: Michael Rethwisch, UCCE Advisor, Riverside County
3:45 Choosing Alfalfa Varieties for Insect, Nematode, and Disease Resistance and high yield: Dan Putnam, UC Davis
3:57 Viable Strategies for Production of Alfalfa in a Drought Year using LESA and MDI on Overhead Sprinklers: Umair Gull, UC Davis Graduate Student
4:09 Soil Health under Full and Deficit Irrigation Conditions: Michelle Leinfelder-Miles, UCCE Advisor, San Joaquin and Delta Region
4:21 Sugarcane Aphid Control in Forage Sorghum: Nick Clark, UCCE Advisor, Kern/Fresno Counties
- Author: Michelle Leinfelder-Miles
- Author: Brenna Aegerter
In 2020, we completed a three-year on-farm trial in the Delta to evaluate warm-season legume cover cropping between winter small grain forage crops. Cover cropping is a management practice identified in the Healthy Soils Program of the California Department of Food and Agriculture as having the potential to improve soil health, sequester carbon, and reduce greenhouse gas emissions. Our objectives were to evaluate summer cover cropping for its potential to improve soil tilth at a time of year when the soil would usually be fallowed and dry with no soil cover, and to better understand the agronomic practices that might make summer cover cropping more feasible for Delta farmers. This article summarizes select results from the trial. A detailed report is available on the Delta Crops website.
The trial took place over 4.5 acres of a commercial field, and we compared a cowpea (cultivar ‘Red Ripper') cover crop treatment (CC) to fallow soil (No CC). The cultural practices varied across years (Table 1). Irrigation was only applied to the cover crop plots. In 2020, we estimated that five inches of irrigation was applied to the cover crop, using surface water with moderately low salinity (seasonal ECw of 0.5 dS/m).
Table 1. Agronomic practices during the three-year study.
We soil sampled twice per year. The first sampling occurred following triticale harvest but prior to tillage and cover crop planting. The second occurred at the end of the cover crop season immediately prior to cover crop termination. Soil was sampled from 0-6, 6-12, 12-24, and 24-36 inch depths. We evaluated bulk density, salinity (electrical conductivity, ECe), pH, total nitrogen (N), and total carbon (C). Additionally, in-situ water infiltration was measured at the conclusion of the project (i.e. prior to 2020 cover crop termination). We hand-harvested cover crop biomass, separated it into cultivated cowpeas, volunteer small grains, and weeds and analyzed each component for total C and N. We hand-harvested triticale forage in 2019 and 2020.
Soil properties. After three years of cover cropping, we did not observe improvements in total N or bulk density from cover cropping, and our statistical analysis indicated that total C was impacted by plot location. This suggests that an inherent soil characteristic, like texture, was having more of an impact on total C than the cover crop treatment. We observed better water infiltration in the CC plots (Figure 1). Cover crop roots likely contributed to better soil structure and water conductance. We also observed lower salinity and higher (i.e. less acidic) pH in the CC plots. Root zone salinity (0-36 in) averaged 1.4 dS/m in the CC plots and 2.2 dS/m in the No CC plots. Root zone pH averaged 5.7 in the CC plots and 5.5 in the No CC plots. These results suggest that cover cropping can improve certain soil characteristics, particularly those related to soil-water status, on a relatively short time frame. Changes in nutrients and C storage, however, are less likely to be observed following short-term changes in management.
Figure 1. Three years of cover cropping improved water infiltration (P=0.0198) compared to the standard dry fallow. The error bars represent the standard errors. The photo illustrates how there were visible differences between treatments, even after triticale forage harvest and uniform tillage operations. No CC soil was a fine powder (bottom of the photo); whereas, CC soil was observed to have better aggregation. The grower observed differences in subsequently-planted small grains, with seedlings in the CC plots emerging about five days earlier than seedlings in the No CC plots.
Cover crop stand. Cover crop composition varied over the course of the study and was likely impacted by cultural practices, like planting and irrigation methods. While cowpea was the only seed planted, the stand was a mix of cowpea, volunteer wheat/triticale, and weeds. We observed that the 2020 practices and timing of operations resulted in the least amount of weed growth (Figure 2) and seed heading.
Figure 2. Proportion of cowpeas, small grains, and weeds in total cover crop biomass, and total C and N inputs from the cover crop.
Triticale forage yield. Despite certain soil health benefits, cover cropping did not improve triticale forage yield. The No CC treatment yielded higher than the CC treatment across both years (Figure 3). The CC plots yielded below the two-year field average of 5.5 tons per acre, and the No CC treatment yielded above the field average yield. Given the improved infiltration, pH, and salinity conditions in the CC treatment, the yield result is difficult to explain, but machine harvesting over a larger area might lessen the difference between treatments.
Figure 3. Triticale forage yield as tons of dry matter per acre. The No CC treatments yielded higher than the CC treatments across both years (2019-2020) (P=0.0059).
Summary. In our three-year study, cover cropping had no effect on total N, bulk density, and total C, but water infiltration, salinity, and pH were improved. Triticale forage (i.e. cash crop) yield did not improve as a result of cover cropping, however. Cowpea stand establishment and volunteer grain and weed competition were the biggest challenges to growing a summer cover crop at this site, but earlier planting and termination reduced the weed pressure. Despite these challenges, the grower observed better soil aggregation in areas of the field where the cover crop had grown. Overall, the potential benefits of cover-cropping may not be realized in the first few cover crop cycles, which could hinder long-term adoption. Results may also depend on the cover crop biomass obtained and other site-specific factors. While scientific studies have demonstrated soil health and cash crop yield improvements with cover cropping, more long-term studies are needed in California to demonstrate how these benefits can be realized.
Acknowledgments. This project was supported by the California Climate Investments program. We thank Dawit Zeleke, Morgan Johnson, and Jerred Dixon of Conservation Farms and Ranches for hosting the trial. We thank Tom Johnson of Kamprath Seed and Margaret Smither-Kopperl and Valerie Bullard of the NRCS PMC for information and advice on cover cropping.
Weeds are important pests of California rice systems, and weed management can account for roughly 17 percent of total operating costs (Espino et al., 2016). Integrated weed management uses cultural and chemical practices where herbicide are important tools. Certain conditions in California rice production systems, however, increase the likelihood of developing herbicide resistance. Herbicide resistance is the ability of certain weed biotypes to survive certain herbicide treatments when the weed species is usually killed by that herbicide (Al-Khatib et al., 2019). Such conditions include, but are not limited to, lack of crop rotation, the efficacy of certain herbicides on certain weeds causing them to get frequently used, and not having diverse chemistries available.
In 2019 and 2020, trials were conducted to evaluate the efficacy of a new herbicide product called Loyant (florpyrauxifen-benzyl; group 4 herbicide; Corteva Agriscience) in drill-seeded rice in the Delta region. Loyant is registered in rice growing states in the southern US but would be a new chemistry in California. Corteva Agriscience expects to have CA registration in time for the 2021 use season. The objective of the trials, by assessing different rates and treatment combinations, was to understand the efficacy and crop tolerance of Loyant for weed control in drill-seeded rice in California. This article will describe select results of the 2020 trial. Treatments are listed in Table 1 below. Complete information from both years is available from my website.
Crop injury. We made crop injury observations and weed counts on 7-day intervals for about two months following treatment. We observed tip burning in several of the treatments, but the symptoms were no longer apparent by 21 days after treatment (DAT). We observed leaf curling in the Loyant treatments until about 56 DAT. Corteva Agriscience has observed this symptom with Loyant in other trials where environmental stressors impact crop health, such as extreme cold or heat, drought, or poor fertility. We observed this symptom on the side of the plots closest to the field edge. We observed no stunting, stand reduction, or differences in heading with any treatments.
Weed control. Overall weed pressure was relatively low, observing about 1 weed per square foot in an untreated strip next to the trial. The prominent weeds in the field were Echinochloa species (i.e. watergrass, barnyardgrass; Figure 1, below). We did not have a completely untreated control but instead considered the pre-emergent only treatment (i.e. Prowl) the control. There was a trend for the Prowl treatment to have the highest weed counts. The treatments that had the best weed control were the grower standard and Loyant/SuperWham herbicide programs (Table 2, below).
Yield. We found no differences in yield, but there was a trend for the grower standard and the Loyant/SuperWham herbicide programs to have slightly higher yields (Table 3, below). Measured yields were uncharacteristically high for the region. Our explanation of the data is that we did our hand harvest in the early morning hours when there was a heavy dew. Because variability across the replicates was low, as indicated by the coefficient of variation, we believe the data demonstrate relative comparability of herbicide programs, even though the absolute values are high.
Conclusions. The purpose of the trial was to learn the efficacy and crop tolerance of Loyant (florpyrauxifen-benzyl) for weed control in California drill-seeded rice. We observed Loyant to have good activity on watergrass and barnyardgrass, which were the predominant weeds in the trial. We observed Loyant treatments to have similarly low weed counts compared to the grower standard, and a Loyant/SuperWham herbicide program appears to provide comparable weed control to the grower standard. The results demonstrate that Loyant could be used in drill-seeded rice herbicide programs, providing a different chemistry for herbicide resistance management.
The aforementioned 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. Herbicide treatments in the 2020 trial. Treatments were applied on May 8th, when the rice was approximately at the 3rd leaf stage.
Figure 1. Predominant weeds in the trial were watergrass and barnyardgrass.
Table 2. Weed counts on 7-day intervals from 14 DAT to 42 DAT. Data represent total number of weeds in the 400-ft2 plot and are the means across four replicates.
Table 3. Yield adjusted to 14 percent moisture. The trial was hand-harvested on Sept. 29, measuring one 10.8-ft2 (1-m2) quadrat per plot. The grower reported that harvest moisture was around 18.5 percent.