- Author: Drew Lyon
- Posted by: Gale Perez
In my previous position as the Extension Dryland Cropping Systems Specialist with the University of Nebraska Panhandle Research and Extension Center in Scottsbluff, I focused my research efforts on intensifying and diversifying the winter wheat-fallow cropping system. The addition of summer crops into the rotation was a first step. Inserting summer crops such as proso millet, sunflower, or corn reduced the frequency of summer fallow from every other year to once every three years. Summer crops also helped in the management of winter annual grass weeds such as downy brome, jointed goatgrass, and feral rye. As I looked for ways to eliminate summer fallow from the rotation, my attention turned to forage crops.
Forage crops are typically harvested at about 50% heading (grass crops) or flowering (broadleaf crops). This is often six or more weeks earlier than if the crops were harvested for grain. This earlier harvest provides a couple of benefits. First, it decreases soil water depletion. Water use by crops is typically greatest from the boot or flower bud stage through early grain fill. By harvesting the crop shortly after the start of this heavy water use time, valuable soil water is conserved for the following grain crop, which in western Nebraska, was often winter wheat. The earlier harvest also prevented seed production in many weeds growing in the forage crop. Taken together, these two benefits made forage crops a good alternative for summer fallow. However, there were obstacles to the use of forage crops such as a lack of forage harvesting and handling equipment and limited local markets.
When I arrived in Pullman, WA in 2012, the focus of my program shifted to weed management in wheat production systems. One of the first new weed species I learned about was Italian ryegrass. Italian ryegrass biotypes have developed resistance to eight different herbicide modes of action, which makes managing Italian ryegrass with herbicides very difficult. Some growers have turned to forage crops to help them manage Italian ryegrass.
At a Washing State University (WSU) Weed Science Field Day a few years back, we had a grower tell us that one of his approaches for managing Italian ryegrass was to plant forage barley and harvest the forage barley and Italian ryegrass before they headed and sell it in small bales to horse owners. Italian ryegrass is an excellent forage, and the bales fetched a good price. I thought that was an excellent out-of-the-box approach for managing this very troublesome weed. I could see a similar approach working for feral rye or wild oat management.
I have also noticed that some growers with Italian ryegrass issues have planted alfalfa to manage the problem. Here, Roundup Ready alfalfa could help in the establishment year, but after that, the simple act of harvesting the alfalfa before Italian ryegrass sets seed is all that would be needed. A perennial crop like alfalfa also brings other crop rotation benefits for weed control. Once established, alfalfa competes strongly with annual weeds. The seed of most annual grasses do not survive long in the soil, so keeping alfalfa in for just three or four years will significantly decrease the soil seedbank of annual grass weeds and allow a return to annual cropping with much lower grass weed pressure.
Despite the obstacles to the adoption of forage crops in our dryland cropping systems, forage crops do offer several benefits for weed management. As herbicide resistance becomes more problematic throughout the region, non-chemical approaches to weed management will become more important. I would love to hear how you have used forage crops in your rotation to manage weeds. Please leave a comment so that others can learn from your experience.
Thanks!
Dr. Drew Lyon
Endowed Chair Small Grains Extension and Research, Weed Science
Washington State University
(drew.lyon@wsu.edu)
Original source: Weeders of the West blog | April 25, 2024
- Author: Jorge Antonio Angeles
- Posted by: Gale Perez
Silverleaf nightshade, Solanum Elaeagnifolium, is perennial weed that is native to South America, Mexico, American Southwest and Southern States. This herbaceous and woody summer weed belongs to Solanaceae just like other weeds such as black nightshade (Solanum nigrum), hairy nightshade (Solanum physalifolium) and horsenettle (Solanum carolinense). It can be found throughout California and in grows in desert and semi-arid areas. Silverleaf nightshade is often found growing in different cropping systems, rangeland, pastures, roadsides, and disturbed areas. Silverleaf nightshade is highly adaptable and can tolerate a wide range of soil and climatic conditions such as high temperatures, low rainfall, saline and drought conditions. The leaves and berries produced by silverleaf nightshade plants have glycoalkaloid compounds that can be toxic to livestock and humans if consumed (UC IPM) (Boyd 1982).
Life Cycle
Impacts
Silverleaf nightshade is becoming a problematic weed in some young pistachio orchards in Tulare, Kings and West Fresno. This perennial weed is mostly found in young orchards that are planted on west Fresno and Kings County by interstate 5 highway (Figure 3). In Tulare County, silverleaf nightshade is found pistachio orchards that were planted in unmanaged fallow land or in fields near roadsides where it's commonly found. One of the major impacts of silverleaf nightshade is that it competes with young pistachio orchard for resources such as water, light and nutrients. If left unmanaged, silverleaf nightshade can also interfere with irrigation operations and potentially reduce crop vigor in young pistachio trees (Figure 2). Since silverleaf nightshade can adapt to alkaline and saline soils, it will also outcompete many of the summer annual weeds and become the dominant weed in the population.
Management
Silverleaf nightshade can be a weed that is difficult to control with the available management methods in orchards. Tillage is not recommended as that is one of the ways that rhizomes can be spread across the orchard (Ensby 2011). Mechanical control methods such mowing can be an effective control method to prevent weeds from setting seed. Flail mowers are often used in orchards and vineyards to mow weeds in between tree rows. It is important to note that, new silverleaf nightshade shoots will potentially sprout from the root system after the tops are mowed (Stanton 2011). Even though mowing can be an effective weed control method during the growing season, most commercial mowers will miss the weeds that grow in between trees that directly compete with young trees. Hand weeding can be used to remove some of the weeds around the trees, but extra precaution needs to be taken. Mature silverleaf nightshade plants are covered in reddish prickles that can be harmful if weeds are handled with bare hands. Weeding tools such as shovels and hula hoes can damage surface drip hoses if the user is not careful.
Herbicides can be an effective weed management method to control silverleaf nightshade in different tree crops. There are a twelve pre-emergent and thirteen post-emergent herbicides with different sites of action that are registered for use in pistachios (Table 1). Pre-emergent herbicides are normally applied during the dormant season and most only control weeds before they germinate. Pendimethalin, rimsulfuron, mesotrione, flumioxazin, isoxaben, and flazasulfuron are herbicides that have great control over black and hairy nightshade. Isoxaben can suppress silverleaf nightshade, but cannot be used in pistachios that have not been established for at least three years. Pre-emergent herbicides will not control silverleaf nightshade that emerges from rhizomes in the summer. Post-emergent herbicides can be used to control silverleaf nightshade that emerges in the summer and early fall before harvest. Glyphosate, glufosinate, pyraflufen, and carfentrazone are post-emergent herbicides with different sites of action that can be used to control different weeds and can be used up to two weeks before harvest. 2, 4-D is another post-emergent herbicide that is registered for use in pistachios, but needs to be applied to trees that have been established for at least one year and has a pre-harvest interval of 60 days. Research work from other researchers has shown that glyphosate and 2, 4-D have excellent control of silverleaf nightshade (DiTomaso 2013) (Gitsopoulos 2017). Glyphosate is a systemic herbicide that can potentially kill the root system of silverleaf nightshade, when applied at the correct timing and rate. Since Silverleaf nightshade has extensive rhizome root systems, the root systems need to be killed to fully control this weed. In the summer months, a combination of mowing and the use of post-emergent herbicides can kill the aboveground tissues of silverleaf nightshade weeds and deplete the root bank in the soil (Heap 2018). Post-emergent herbicides need adjuvants such as nonionic surfactants, crop and seed oils, to increase their efficacy. Furthermore, always consult the herbicide labels on information regarding information on the required adjuvants, pre-harvest intervals, application rates and maximum applications per seasons.
The weed management tools to control silverleaf nightshade in pistachio orchards are limited. Developing and maintaining field records before planting is a great way to determine the history of a field before planting. Conducting weed surveys in the winter and spring can help determine what weed species are present in a field. Silverleaf nightshade populations can be reduced by mowing in between tree rows and applying herbicides to weeds present in between trees. These management practices need to be done before the weeds set seeds to contribute to reduce the seedbank. To avoid introducing silverleaf nightshade to other fields, it is important to sanitize tractor equipment and manage the weeds that grow on the field edges or near irrigation canals (. To have an effective silverleaf nightshade management program, a combination of herbicides with different modes of action are needed decrease the possibility of it developing herbicides resistance. Silverleaf nightshade is difficult to control because of its tolerance to many herbicides (Gitsopoulos 2017). During the summer months, it is best to use a combination of systemic and contact post-emergent herbicides to get higher levels of control for silverleaf nightshade. To enhance the efficacy and herbicide absorption, post-emergent herbicides require adjuvants such as methylated seed oils, non-ionic surfactants, crop-oil concentrates, and nitrogen-based fertilizers.
Cited Literature
Boyd, J.W. and Murray, D.S. 1982. Growth and development of silverleaf nightshade (Solanum elaeagnifolium). Weed Science 30, 238-43.
DiTomaso, J.M., G.B. Kyser et al. 2013. Weed Control in Natural Areas in the Western United States. Weed Research and Information Center, University of California. 544pp.
Ensbey R. 2011. Noxious and environmental weed control handbook – A guide to weed control in non-crop, aquatic and bushland situations. 6th ed. New South Wales: Department of Trade and Investment, Regional Infrastructure and Services.
Gitsopoulos, Thomas & Damalas, Christos & Georgoulas, Ioannis. 2017. Chemical options for the control of silverleaf nightshade (Solanum elaeagnifolium). Planta Daninha. 35. 10.1590/s0100-83582017350100064.
Heap, J. & Wu, H. 2018. Silverleaf Nightshade: Australian best practice management manual. Primary Industries and Regions SA & NSW Department of Primary Industries: Adelaide.
Roberts J., Florentine. 2022. Biology, distribution and management of the globally invasive weed Solanum elaeagnifolium Cav. (silverleaf nightshade): A global review of current and future management challenges. Weed Res. 2022;62:393–403. doi: 10.1111/wre.12556.
Stanton, R. & Wu, Hanwen & Lemerle, D. 2011. Root regenerative ability of silverleaf nightshade (Solanum elaeagnifolium Cav.) in the glasshouse. Plant Protection Quarterly. 26. 54-56.
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- Posted by: Gale Perez
Job #JPF01902
Location: Riverside, CA
APPLICATION WINDOW
Open date: April 17, 2024
Next review date: Wednesday, Jun 12, 2024 at 11:59pm (Pacific Time)
Apply by this date to ensure full consideration by the committee.
Final date: Sunday, Jun 30, 2024 at 11:59pm (Pacific Time)
Applications will continue to be accepted until this date, but those received after the review date will only be considered if the position has not yet been filled.
Job Description: https://aprecruit.ucr.edu/JPF01902
POSITION DESCRIPTION
The Department of Botany and Plant Sciences at the University of California Riverside invites applications for an Assistant Professor of Extension (Assistant Specialist in Cooperative Extension) in the area of weed management in agronomic crops. This is a fiscal year position available July 1, 2024 with an 80% Cooperative Extension and 20% Organized Research Appointment in the Agricultural Experiment Station (http://cnas.ucr.edu/about/aes/). The position will be housed at the University of California Riverside campus in Riverside, CA. The successful applicant will develop an internationally recognized, extramurally funded basic and applied research program on the management of non-aquatic weeds using chemical and non-chemical strategies that decrease weed competition, minimize environmental impacts from weed control practices, and reduce the economic costs of weed management. Preference will be given to candidates conducting research at the forefront of their field who have a strong working knowledge of weed management and control and a desire and ability to work with diverse clientele. Cooperative extension (CE) responsibilities include the development and implementation of educational programs on weed management in agronomic crops, which may include extension publications, newsletters, web pages, blogs, field days, participation in CE Advisor meetings, organizing workshops, and contributing to the University of California Agriculture and Natural Resources (UC ANR) workgroups and teams.
The current base pay range for the Assistant Professor of Extension position is $84,100 to $110,100 and the Agronomist/ Organized Research position is $86,500 to $112,800. Additional off-scale to be commensurate with market value, qualifications and experiences.
Required qualifications for this position that must be met by the date of application include: a Ph.D. in Weed Science, Agronomy, Plant Sciences or a related discipline, demonstrated experience in applied research, and excellent communication and interpersonal skills.
Preferred qualifications for this position include: Postdoctoral experience, experience in research and outreach with demonstrated productivity in publishing in journals related to weed management, and a track record of success in obtaining extramural funding.
Advancement through the Professorial ranks at the University of California is through a series of structured, merit-based evaluations, occurring every 2-3 years, each of which includes substantial peer input.
To apply: submit the following to https://aprecruit.ucr.edu/apply/JPF01902.
- Cover Letter – short cover letter describing background and interests
- Curriculum Vitae
- Statement of Teaching and Mentoring - This statement should be a concise description of the applicant's teaching and mentoring philosophy and include past experience and future teaching and mentoring plans (2-page maximum)
- Statement of Research interests and goals (3-page maximum)
- Statement of Extension interests and philosophy (2-page maximum)
- Statement of Past and/or Planned Future Contributions to Advancing Diversity and Inclusive Excellence (2-page maximum)
- 3 Letters of Reference – At time of submission, applicants should provide contact information and request letters of recommendation from 3 referees to be submitted through AP Recruit, Letters will need to be submitted to AP recruit from the letter writers by June 12, 2024.
- Up to 3 select reprints of publications or manuscripts in press (optional)
Review of applications will commence on June 12, 2024, and proceed until position is filled. For full consideration, applicants should submit their complete applications prior to the above date.
For the FULL JOB DESCRIPTION: https://aprecruit.ucr.edu/JPF01902
For more information about this position, please contact Dr. Milt McGiffen, Chair of the Search Committee, Department of Botany and Plant Sciences, at milt@ucr.edu. For questions on application procedures and requirements, please contact Mrs. Naudia Samuels Johnson, Academic Personnel, at naudia.samuelsjohnson@ucr.edu.
- Author: Giuliano Carneiro Galdi
- Posted by: Gale Perez
Roundup Ready technology incorporates genetic resistance to glyphosate into crops and it's an excellent tool for weed control. Initial screening in the early 2000s found good alfalfa crop safety, and many growers currently rely on glyphosate as the only herbicide. Although using the same herbicide over and over is not a good idea because it may accelerate herbicide resistance in weeds, Roundup Ready alfalfa has been successfully used with few to no concerns regarding crop safety. However, the combination of glyphosate and cold weather may cause crop injury, especially in certain regions.
The problem was first observed in 2014 by Steve Orloff, former UCCE farm advisor in Siskiyou County. A Roundup Ready alfalfa field showed injury after glyphosate application followed by a frost event. The main symptoms were plant stunting, chlorosis, and “shepherd's crook”, in which individual alfalfa stems curl over and die (Figures 1 and 2). Yield reductions were also observed for the first cutting. It was clear to Steve the injury was somehow related to the glyphosate application because a section of the field where the wheel line was sitting was not sprayed and it looked perfectly normal.
Interestingly, the injury seen was very similar to symptoms caused by frost and/or bacterial blight caused by Pseudomona syringae – a bacteria that is present everywhere. The bacteria can exacerbate frost damage due to its protein that mimics a crystalline structure and provides a starting point for ice formation, damaging the plant tissue and serving as an entrance port into the leaves and stems. Once into the plant tissue, colonization leads to infection and symptoms about 7-10 days after the frost event. Symptoms on stems start as water-soaked lesions that extend down one side. Leaves become water-soaked and often are twisted and deformed.
Steve was able to replicate the symptoms in field trials conducted in 2015, 2016, and 2017. The field trials showed yield reductions of up to 0.7 ton/acre in the first cutting in Scott Valley. Crop injury was not observed in a similar field trial conducted in 2014, probably because there was no frost event after glyphosate application. Similar impacts were observed in a trial in the intermountain region near Tulelake, CA; additional yield reductions were observed with higher glyphosate rates (Table 1).
Based on this work, a multi-year project started to investigate the effects of glyphosate rate and application timing during various seasons at 24 sites over five years, measuring the impact on alfalfa crop height and biomass yield. Results were published in the Agronomy Journal in 2023 (Loveland et al, 2023). All sites in this study were in the Intermountain West (California and Utah). Results showed that while summer glyphosate application did not injure alfalfa, spring applications reduced crop height at 76% of the sites and biomass at 62% of the sites. In sites where glyphosate application resulted in crop injury, low (22 oz/A) and high (44 oz/A) rates of glyphosate reduced yields by 0.24 ton/A and 0.47 ton/A, respectively. Data also show that the crop height at glyphosate application influenced the degree of injury (Figure 3), with greater yield reductions at 30 – 40 cm than at 5 to 10 cm height.
As alarming as the possibility of injury might sound, its occurrence and degree are widely variable, and most fields will resume normal growth and yields after first cutting. Figure 4 illustrates this complexity and variability throughout experimental sites where harvest yield and crop height were assessed. Note that the locations represented in the following graph are colder than the San Joaquin Valley and the injury happened after glyphosate applications in the spring.
As of 2024, this type of injury has only been reported in the intermountain west due to its high altitude and cooler weather. However, one field I visited in early February in Firebaugh brought my attention back to the issue. The field was planted in the fall of 2023 and had many of the symptoms described above: plant stunting, typical shepherd's crook, chlorosis, and dead stems. While all these symptoms could be exclusively due to bacterial blight infections or frost, parts of the field where glyphosate application was accidentally skipped looked better.
Current UC IPM weed management guidelines for RR alfalfa recommend rotating herbicides with different modes of action to reduce the development of herbicide resistant weeds and avoid glyphosate overuse during the colder winter months. Second, spray glyphosate when the alfalfa is short (< 2”) when using the higher rate (44oz/A) or 4” when spraying at the lower rate (22oz/A). Third, use the lowest glyphosate rate possible according to the weeds present and their stage of development. Finally, pay attention to the weather forecast. Applying glyphosate before frost events increases the likelihood of crop injury, especially in old stands.
Reference
Loveland, L.C., Orloff, S.B., Yost, M.A., Bohle, M., Galdi, G.C., Getts, T., Putnam, D.H., Ransom, C.V., Samac, D.A., Wilson, R., and Creech, J.E. (2023). Glyphosate-resistant alfalfa can exhibit injury after glyphosate application in the Intermountain West. Agronomy Journal, 115, 1827–1841. https://doi.org/10.1002/agj2.21352.
- Author: Daniel K Macon
Barb goatgrass (Aegilops triuncialis L.) is a winter annual grass native to the Mediterranean region and western Asia. According to a UCANR publication, it was introduced to Sacramento and El Dorado Counties via the importation of cattle from Mexico. And it is a growing problem on annual rangelands here in the Sierra Foothills. In some ways, I think of this invasive grass as "medusahead on steroids" - barb goatgrass spikes and joints (seedheads) disperse by attaching to animals, humans, and equipment. I often see new infestations along roads or walkways. Barb goatgrass forms dense stands with a rapidly establishing root system, making it extremely competitive with other annual grasses and forbs. In some areas, barb goatgrass reduces forage quality and quantity by as much as 75 percent - and because livestock tend to avoid the plant (and graze more desirable forages), it can spread rapidly.
Carol and Andy Kramer, who operate a sheep and cattle ranch in Nevada County, have been fighting barb goatgrass for several years. Most recently, they've been working with the Natural Resource Conservation Service (NRCS) through an Environmental Quality Incentives Program contract focused on goatgrass control. Over the course of the last 9 months, Carol and Andy have been working with the Placer Resource Conservation District (RCD) and UCCE to experiment with using prescribed fire to reduce goatgrass and re-invigorate native grasses.
Research suggests that burning goatgrass for two consecutive years offers "excellent control." Sounds pretty straightforward, right?! Not so fast! Fire is an effective control method when most of the fine fuel has dried sufficiently to carry the fire, but when the goatgrass seedheads are still attached to the stem - in other words, in late spring or early summer, when everyone is starting to get nervous about fire in the foothills!
A quick aside about using prescribed fire as a range improvement tool. When I started working with ranchers in California in the early 1990s (when I was just out of college, working for the California Cattlemen's Association), prescribed fire had largely gone out of vogue. This was partly a result of increasing worries about liability, and partly, as I recall, a shift in focus and attitude within the California Department of Forestry and Fire Protection (which became officially known as CalFire in the early 2000s). Today, after a decade of increasingly catastrophic wildfires (and the accelerating spread of invasive weeds like barb goatgrass), prescribed fire is making a comeback - thanks to efforts of many of my UCCE colleagues, RCD staffers and contractors like Cordi Craig and Chris Paulus (who led this effort), and especially of landowners like Carol and Andy!
Obviously, with something as complicated as prescribed burning, you don't simply wake up one June morning and say, "Hey, this would be a great day to light the back pasture on fire!" Carol and Andy (along withCordi and Chris, andUCCE) began planning for this burn last winter. As fire professionals,Cordi and Chris recommended putting a "black line" around the 1.5 acres ofgoatgrass during the winter months, whenCALFIRE burn permits are not required. Carol and Andy invested in water tanks and other equipment, and spent much of the winter and early spring pile burning and creating fire lines. Working together, we also burned several adjacent units to remove ground and ladder fuels in the areas surrounding thegoatgrass site.
Then we all waited! We needed the underlying fuel to be dry enough to burn, but we also needed the goatgrass to hold onto its seedheads. And we needed the right weather conditions. With the wet, cool spring we had in 2023, these conditions didn't arrive until July - well into fire season. This meant that we also needed a permit from CalFire. I've lived and worked in CalFire's NEU unit (which covers Placer, Nevada, and Yuba Counties) - and worked with and around ranchers - for nearly 30 years. I wasn't aware of CalFire ever allowing a rancher to do a prescribed fire for range improvement (or any other reason) in July. But thanks to the Kramer's persistence and Cordi and Chris's experience and knowledge, we received permission to do the burn on July 13.
Carol and Andy started the fire around 9am that morning - temperatures were hovering around 80F, and the relative humidity was just over 50%. Amazingly, we had difficulty getting the vegetation to burn - even as temperatures rose and humidity dropped over the course of the morning. By midday, we'd burned all we could burn, and began mopping up (making sure the fire was completely out).
Walking through the burn, I was amazed by the variability in burn intensity. Some of the goatgrass seedheads were completely consumed; others looked like they had not been exposed to fire at all. Carol collected seedheads from before the burn, as well as singed and apparently unsinged seedheads, to see if there will be any difference in germination (we'll keep you posted). We also started thinking about next year's burn.
One of the biggest challenges in burning for a second consecutive year, I expect, will be whether there is enough fine fuel (other grasses, pine needles, dry leaves, etc.) to carry the fire through the goatgrass. Visiting the site two weeks ago, I was impressed to see native blue wildrye starting to grow in the blackened burn unit (even with very little precipitation since the fire) - we'll be anxious to see what happens once we've had a germinating rain. Even so, we are considering broadcasting a quick-growing, early maturing annual grass (like soft chess (Bromus hordeaceus) this fall so that we have more receptive fuel next spring.
I think we all learned a great deal about the logistics of using fire to manage goatgrass (thanks to Cordi and Chris) - and about the challenges of using prescribed fire during fire season. One of the side benefits, from my perspective, is the demystification of fire generally. This was not a scary burn, even though it happened in the middle of July! While this was partly due to the conditions on the day of the burn, the work that Carol and Andy did to prepare (with Cordi and Chris's guidance) over the many months leading up to July 13 made it successful and safe. We're all looking forward to next year's fire!