- Author: Konrad Mathesius
Summary Review
Results from this year's Italian ryegrass (IR) herbicide trials helped quantify differences in herbicide resistance among IR populations within the southern Sacramento Valley. The trial took place in Bird's Landing, CA (near Rio Vista), and was replicated farther north in Esparto, CA.
- Trials from this year suggest that Osprey-resistant IR populations often associated with the area around Dixon, CA could extend at least as far south as Bird's Landing with only 26% control of IR by Osprey in the trial site.
- The Osprey-resistant population appears to also be moderately resistant to Simplicity, another herbicide in the same chemical family, which only provided 60% control at the Bird's Landing site.
- Axial (an ACCase inhibitor) worked well at controlling IR in Bird's Landing (92% control).
- In Esparto, IR in the trial was somewhat more susceptible to ALS inhibitors. IR control was only around 80% with Simplicity.
Introduction
For a few years I've heard PCAs mention that Italian ryegrass (IR) populations around Dixon are showing resistance to Osprey (an ALS inhibitor herbicide), but quantification of differences in weed control can help provide a better understanding of what growers are dealing with. IR is notorious for its capacity to develop herbicide resistance to multiple modes of action (MoA). As an obligate outcrossing plant, IR must cross-pollinate in order to produce viable seed. This means that genetic material is regularly exchanged during pollination, which allows populations to respond to environmental pressure. Development of herbicide resistance in IR over the years has caused increasing concern for small grain growers, who are limited in their options for control.
This study is part of a wider range of studies examining different options available to growers for IR control in small grains. This study quantifies the efficacy of various available herbicides on IR populations in small grains both in the northern parts of Yolo County and the southern parts of Solano County.
Methods
Two trials were set up: one in Bird's Landing and one in Esparto. Each plot was 15 x 100 feet and was replicated 4 times at each location. Plots were planted with wheat in late December 2022 after a burndown treatment and were treated in January of 2023 using the maximum label rate of each herbicide along with recommended adjuvants (Table 1). A 20ft x 15ft section of each plot was left unsprayed as an untreated reference. Axial was unintentionally applied at half label rate in Esparto.
Prowl was tested to see if it might improve control by by providing residual control of late germinating ryegrass that escaped preseason control efforts but did not germinate with the first fall rains. IR control was not significantly better in the Prowl tankmix vs Simplicity applied alone in this experiment.
Treatments and Rates Evaluated for Italian ryegrass Control in Two Wheat Sites in 2023 in the Sacramento Valley.
Weed counts were taken in late February in each plot (3 sub-samples). The untreated reference sections within each plot were measured once (1 representative sub-sample). Percent weed control was measured by the difference in ryegrass density within the treated and untreated areas in each plot.
Grain was hand harvested in late July using 3 x 4ft^2 quadrats in each plot. Spikes were collected by cutting the stem at the base of the spike using a sickle. Samples were then air dried. Grain yield was determined by subtracting an estimated chaff weight of 17% from the weight of the harvested spikes (McCartney et. al, 2006).
Results and Discussion
Percent control
Within each location, herbicides varied significantly in terms of the capacity to control IR.
In Bird's Landing (20 miles south of Dixon, CA), Axial provided significantly better IR control than Simplicity, Prowl + Simplicity, and Osprey. Osprey did not reduce IR populations compared to the non-treated control plots. (Figure 2)
In Esparto, a tank mix of Prowl + Simplicity provided better control of IR than Osprey but was not different than Simplicity alone (p = 0.52) or the tank mix of Axial + Simplicity (p = 0.81). Osprey provided only moderate control (58%) and was marginally different from Simplicity (p = 0.084), which provided 79% control.
The differences in control between the two ALS-inhibitor herbicides (Simplicity and Osprey) at the two locations are an indication of the variation among IR populations that are only 50 miles apart.
Yield
Yield results collected from the Bird's Landing site show trends that generally correspond with differences in weed control, although no significant differences in estimated yield were found due to the variability of the data.
Conclusion
Variations in herbicide efficacy are a good reminder that there is a lot of genetic variability in IR populations; even fields only a few miles apart could have important differences in response to herbicides. This means that grower practices can directly impact the development of herbicide resistance in their area. Growers in the Dixon area should incorporate IPM practices listed above and consider the use of Axial as an alternative weed control if they haven't already, and growers farther north should remain particularly vigilant about preserving the efficacy of their ALS inhibitor herbicides by integrating some of the IPM practices listed below.
- Using certified seed (to prevent weed seeds from hitching a ride to entirely different areas of the state)
- Thoroughly cleaning equipment, or operating equipment only within local areas to prevent the spread of weed seed to other parts of the state
- Rotating herbicides within the season and from one season to the next, where possible
- Spraying at the right time (check labels, apply on the early end of the spray window)
- Spraying the right rate (Axial applications in Esparto were sprayed unintentionally at half-rate and provided no control).
- Spraying when weeds are actively growing
- Planting wheat at the right density
- Incorporating mechanical cultivation or Harvest Weed Seed Control where possible
- Checking and calibrating spray nozzles
- Incorporate the use of pre-emergent herbicides labeled in California
- Rotating crops where possible to diversify herbicide programs
- Check for escapes and monitor fields for efficacy
Growers are also encouraged to take advantage of UC IPM resources online, and in-person through their local farm advisors.
References
McCartney, D.H.; Block, H.C.; Dubeski, P.L.; Ohama, A.J. Review: The composition and availability of straw and cha? from small grain cereals for beef cattle in western Canada. Can. J. Anim. Sci. 2006,86, 443–455.
- Author: Konrad Mathesius
If you haven't seen the announcements on the UC Small Grains blog, you should be subscribed to the UC Small Grains blog.
Additionally, a friendly reminder to stop by this Thursday for the UC Alfalfa/ Forages and Small Grains Field Day from 7:30 a.m. until 3:30 p.m.
Location: 2400 Hutchison Dr, Davis CA 38.5390, -121.7800
Alfalfa Talks: 8:00 – 10:00
Small Grains Agronomy Topics: 10:00 -12:00
LUNCH will be provided (please register below)
Small Grains Breeding Program Topics: 1:40 -3:00
Agenda: https://ucanr.edu/sites/small-grains/files/383475.pdf
Register: https://surveys.ucanr.edu/survey.cfm?surveynumber=40606
Continuing Education Units (CEUs): 3.5 CCA; 1.5 CDFA INMP (formerly CURES)
Looking forward to seeing you there.
- Author: Michelle Leinfelder-Miles
The annual UC Davis Alfalfa and Small Grains Field Day will take place on Thursday, May 11, 2023 at the Department of Plant Sciences Field Facility (2400 Hutchison Drive, Davis, CA 95616). Registration opens at 7:30am, and the wagons leave for the field at 8am. The event is free and open to the public, but registration is requested. Lunch is sponsored by the CA Crop Improvement Association, and continuing education credits will be available. Directions are as follows:
The field day is located on Hutchison Drive, just west of Davis. Take the Hwy. 113 exit north from I-80, or Hwy. 113 south from Woodland. Exit west on Hutchison Drive. Take a right at the first roundabout, a left at the second roundabout, and the field headquarters is about ¼ mile down in a clump of trees and buildings on the left.
The agenda is as follows:
8:10 Alfalfa Breeding Efforts at UC Davis - Charlie Brummer
8:20 Choosing Varieties for Pest Resistance - Dan Putnam
8:30 IPM and Importance of Management of Insect Resistance in Alfalfa - Ian Grettenberger
8:40 Test your Weed IQ - Identification of Weeds - Brad Hanson
8:55 Use of Compost to Improve Soils in Alfalfa - Michelle Leinfelder-Miles
9:05 Sorghum Projects for Forage and Biofuels - Jackie Atim
9:15 Improving Agronomic and Grain Quality Traits in Sorghum under Well-watered and Drought Conditions - Christine Diepenbrock
9:35 Flood or Drought? Alfalfa Strategies for Coping with California's Future - Dan Putnam
9:45 Teff as an Alternative Summer Forage Crop - Dan Putnam
9:50 Overhead Irrigation Technologies for Improved Efficiency - Isaya Kisekka
10:05 Updates from UC Davis Small Grains Breeding Program - Jorge Dubcovsky
10:20 Effects of Genotype and Environment on Productivity and Quality in California Malting Barley - Maany Ramanan
10:30 California Grain Foundation and Research on Food Use of Triticale - George Fohner
10:40 Small Grain Research Update from Tulelake - Rob Wilson
10:55 Evaluating Digestate and Hydrolysate as Alternative N Sources in Small Grains - Valentina Roel
11:05 Biosolids as a N Fertilizer Source in California Small Grains - Konrad Mathesius
11:15 Helping Farms in the Central Coast get N Scavenging Credits for Cereal Cover Crops - Eric Brennan
11:25 DIY In-field Plant Tissue Tests to Determine N Sufficiency in Wheat - Karla Estrada
11:30 Updates on Small Grain Research and Production in the Central Valley - Mark Lundy
11:45 Tour Small Grain Variety Trials
12:10 Lunch
1:20 Small Grain Breeding Field Day
- Author: Mark E Lundy
Please join us for upcoming field events hosted by University of California Cooperative Extension:
Nutrient Management Alternatives in Small Grains: Research Updates
4/18/2023 from 8:40 to 10:30
On-farm in Solano County
Click here for details and to register
UC Small Grains and Alfalfa/Forages Field Day
5/11/2023
UC Davis Plant Sciences Field Facilities
Details to follow on the UC Small Grains Blog
- Author: Konrad Mathesius
Nitrogen (N) management in small grains has recently managed to capture more attention than usual due to the high cost of N fertilizers. Several researchers from UC and UCCE have been working on projects that can provide growers with some valuable information on various N management options.
Join us next month (Tuesday April 18, 2023, previously March 22, 2023, rescheduled due to wet field conditions) from 8:40 until 10:30 for some quick updates on research. The field site is an experimental trial run by Cameron Pittelkow evaluating the use of digestate and hydrolysate as a N source in small grains.
Additional details below:
Nutrient Management Alternatives in Small Grains: Research Updates
Tuesday April 18, 2023, 8:40 a.m. – 10:30 a.m.
Field located in Solano County (Runge Road between Dixon and Davis, CA)
Click for GPS location: 38.481688, -121.768429
Please RSVP: click here or use the QR code
8:40 a.m. Registration, light refreshments
9:00 a.m. Welcome and Introduction
9:05 a.m. Approaches and tools for in-season N management
Mark Lundy UCCE Small Grains Specialist
9:30 a.m. Evaluating alternative N sources under the CDFA Healthy Soils Program: Digestate and hydrolysate in small grains and future work
Cameron Pittelkow and Valentina Roel, UC Davis Plant Sciences
9:55 a.m. Biosolids as a N fertilizer source in CA: research results and considerations
Konrad Mathesius, UCCE Agronomy Advisor, Yolo, Sacramento, and Solano
10:20 a.m. Discussions, survey, and grower feedback
10:30 a.m. Adjourn
CE Credits
CCA: 1.5 (pending)
INMP/Cures: 1.5 (pending)