- (Focus Area) Agriculture
- Author: Pershang Hosseini
- Author: Tong Zhen
- Author: Matthew Fatino
- Author: Brad Hanson
- View More...
Broomrapes (Orobanche and Phelipanche spp.) are obligate plant parasites with a broad range of agricultural crop hosts. In non-parasitic plant species, seeds generally initiate germination when exposed to favorable conditions of temperature, humidity, oxygen, and, occasionally, light. However, for obligate parasitic plants like broomrapes, a chemical signal from the host plant is essential. Germination of broomrape can only occur under appropriate soil conditions and when the seed receives a strigolactone chemical signal released from the roots of a suitable host. Strigolactones (SLs) are carotenoid-derived hormones that play a crucial role in various aspects of plant growth and development. Fertilizers can regulate the production of these plant hormones (Xie et al. 2010).
Fertilization can improve soil conditions and lead to reduced initiation of broomrape parasitism (Fernández-Aparicio et al. 2016). Studies have shown that heavy infestations of crenate broomrape (Orobanche crenata Forsk.) on faba beans are linked to lower soil fertility (Trabelsi et al. 2017), and parasitism of Egyptian broomrape on tomato occurs more frequently in low-nutrient conditions (Jain and Foy 1992). The application of fertilizers has been reported to suppress the occurrence of other parasitic plants such as Striga (Jamil et al. 2011) and Egyptian broomrape (Phelipanche aegyptiaca) (Jain and Foy 1992). Fertilizers can reduce parasitism and enhance crop tolerance both directly, through toxic effects, and indirectly by improving soil fertility and plant health.
Direct toxic effect of fertilizers
Nutrient management can enhance both resistance and tolerance to broomrape parasitism in crops at the pre-attachment and post-establishment stages. Increasing the levels of nitrogen (N) and phosphorus (P) in the soil through fertilizer application can reduce the germination and subsequent infestation rates of parasitic weeds (Jamil et al. 2011). Ammonium nitrate combined with potassium phosphate or the use of ammonium phosphate alone proved to be effective in reducing parasitism and promoting the growth of tomato plants compared to potassium sulfate (Jain and Foy 1992). The direct inhibitory effects of nutrients on broomrape seeds can occur during the preconditioning, germination, and seedling elongation stages. Preconditioning Egyptian broomrape seeds in the presence ofammonium salts, such as ammonium sulfate or urea, significantly inhibited their germination; in contrast, nitrate did not have the same inhibitory effect (Jain and Foy 1992). Increasing nitrogen rate (ammonium nitrate) decreased seed germination and radicle length of branched broomrape (Irmaileh 1994). Another experiment showed that nitrogen in the ammonium form resulted in greater inhibition than nitrate, and the inhibition mechanism was actually a reduction in radicle elongation rather than inhibition of germination (Westwood and Foy. 1999).
Down-regulating of Strigolactones (SLs)
Fertilization can protect crops from parasitism by downregulating the synthesis and exudation of strigolactones, which are the most potent germination-inducing factors for root parasites (Fernández-Aparicio et al. 2016). Plants release SLs in different situations, including the establishment of symbiotic relationships between plants and certain soil microorganisms (Besserer et al. 2006; Kapulnik and Koltai 2014) and during stress response (Kapulnik and Koltai 2014). It is likely that plants produce strigolactones as a "cry for help," which broomrape exploits to its advantage. The availability of nutrients, particularly nitrogen, can decrease plant stress and subsequently downregulate the production of strigolactones. Effects of N, P, and K deficiencies on SL production showed that both N and P deficiencies enhanced SL exudation in resistant genotypes of faba bean (Trabelsi et al. 2017) and red clover (Yoneyama et al. 2012), while K deficiency had no effect (Trabelsi et al. 2017). A similar positive effect of low phosphate levels on SL production was also observed in tomato (López-Ráez et al. 2008).
In summary, effective nutrient management is a vital strategy in reducing broomrape parasitism and enhancing crop tolerance. By manipulating soil fertility and nutrient availability, it is possible to directly inhibit broomrape development and indirectly protect crops by downregulating strigolactone production. Appropriate fertilization and other stress-reducing management practices can reduce broomrape parasitism.
In addition to the indirect effects on broomrape, researchers in the Hanson lab are investigating the direct toxic effects of various fertilizers on broomrape seeds during three stages: preconditioning, germination, and post-germination (Figure 1). In future studies, we aim to explore the indirect effects of fertilization on broomrape parasitism, focusing on how nutrient management can influence the production of strigolactones and other related mechanisms. The ultimate goal of this work is to determine if manipulating fertilizer form, timing, or rates could directly inhibit branched broomrape and maximize tomato resilience to broomrape parasitism as part of an integrated management strategy.
a | b | c |
Figure 1: Branched broomrape seeds in different treatment conditions:
a) Germination (elongated radicle) observed in the control group.
b) No germination was observed when ammonium phosphate was applied at the germination stage.
c) Elongated radicle changed color when ammonium phosphate was applied post-germination.
References
Besserer, A., Puech-Pagès, V., Kiefer, P., Gomez-Roldan, V., Jauneau, A., Roy, S., ... & Séjalon-Delmas, N. (2006). Strigolactones stimulate arbuscular mycorrhizal fungi by activating mitochondria. PLoS Biology, 4(7), e226.
Fernández-Aparicio, M., Reboud, X., & Gibot-Leclerc, S. (2016). Broomrape weeds. Underground mechanisms of parasitism and associated strategies for their control: a review. Frontiers in Plant Science, 7, 171714.
Irmaileh, B. A. (1994). Nitrogen reduces branched broomrape (Orobanche ramosa) seed germination. Weed Science, 42(1), 57-60.
Jain, R., & Foy, C. L. (1992). Nutrient effects on parasitism and germination of Egyptian broomrape (Orobanche aegyptiaca). Weed Technology, 6(2), 269-275.
Jamil, M., Charnikhova, T., Cardoso, C., Jamil, T., Ueno, K., Verstappen, F., ... & Bouwmeester, H. J. (2011). Quantification of the relationship between strigolactones and Striga hermonthica infection in rice under varying levels of nitrogen and phosphorus. Weed Research, 51(4), 373-385.
Kapulnik, Y., & Koltai, H. (2014). Strigolactone involvement in root development, response to abiotic stress, and interactions with the biotic soil environment. Plant Physiology, 166(2), 560-569.
Trabelsi, I., Yoneyama, K., Abbes, Z., Amri, M., Xie, X., Kisugi, T., ... & Kharrat, M. (2017). Characterization of strigolactones produced by Orobanche foetida and Orobanche crenata resistant faba bean (Vicia faba L.) genotypes and effects of phosphorous, nitrogen, and potassium deficiencies on strigolactone production. South African Journal of Botany, 108, 15-22.
Westwood, J. H., & Foy, C. L. (1999). Influence of nitrogen on germination and early development of broomrape (Orobanche spp.). Weed Science, 47(1), 2-7.
Xie, X., Yoneyama, K., & Yoneyama, K. (2010). The strigolactone story. Annual Review of Phytopathology, 48, 93-117.
Yoneyama, K., Xie, X., Kim, H. I., Kisugi, T., Nomura, T., Sekimoto, H., ... & Yoneyama, K. (2012). How do nitrogen and phosphorus deficiencies affect strigolactone production and exudation?. Planta, 235, 1197-1207.
/table>HLB Update - Ventura County Detections
There have been no new confirmed positive HLB detections in Ventura since early February, and no recent expansions to the 5-mile HLB quarantine in place in the Santa Paula area. To see a map of the current HLB quarantine areas and other details of HLB detections throughout the state, updated weekly, please visit maps.cdfa.ca.gov/WeeklyACPMaps/HLBWeb/HLB_Treatments.pdf.
Visit Information for Citrus Growers/Grove Managers for the most up to date mitigation requirements for moving bulk citrus to, from, and within an HLB quarantine. Even if mitigation is not required, it is still required for growers to submit an ACP-Free Declaration Form to the applicable county agricultural commissioner's (CAC) office in advance. The ACP-Free Declaration Form has been updated to reflect these changes.
There have been no confirmed positive HLB detections or HLB quarantines in Santa Barbara county to date.
2024 Ventura County ACP-HLB Grower Meeting June 11 - In person or via Zoom
All are welcome. June 11th, 8:30am - 1pm at United Water Conservation District, 1701 Lombard Street in Oxnard, or on Zoom (Meeting ID: 833 1062 0864, Passcode ACPHLB). This meeting has been approved for 4 DPR CEUs (1.25 Laws, 2.75 Other). To receive CEUs you must attend in person and pre-register with DPR at https://cereported/courses/290. If you are not seeking CEUs, there is no registration required.
The full agenda is below.
Citrus Program Leadership Changes
The California Department of Food and Agriculture's (CDFA) Pest and Disease Prevention Division (CPDPD) has announced that as of May 14, 2024, Victoria Hornbaker, former director of the CPDPD, transitioned to her new role as the director of the CDFA's Plant Health and Pest Prevention Services (PHPPS) Division. David Gutierrez, branch chief of the CPDPD, will serve as interim director while a recruitment process is conducted to find a permanent hire for the role. Read Full Article Here
Citrus Pest and Disease Prevention Committee Meetings -- Webinar and In Person
All meeting agendas and eventually the minutes are posted at www.cdfa.ca.gov/citrus committee/. The 2023-24 schedule for the Full Committee is here, and the schedule for Subcommittees is here.
- Executive Subcommittee - June 26
- Finance Subcommittee - July 9
- Operations Subcommittee - July 10
- Outreach Subcommittee - July 17
- Full Committee - August 8
All meetings are free and open to the public to listen to or make public comment. Meetings are currently in person and accessible via phone and/or webinar. Links to register for and join meetings are included in agendas when posted.
For a list of all current committee members, click here.
Important ACP/HLB Documents and Resources
- CDFA Citrus Division website: https://www.cdfa.ca.gov/Citrus/
- Regulatory/Quarantine
oSign up for regulatory updates from the Citrus Pest and Disease Prevention Division at www.cdfa/signup-email-updates.
oInteractive map to find out how close you are to HLB detections.
oRegulatory requirements for moving bulk citrus: Information for Citrus Growers
oSummary of regulatory requirements in the event of an HLB detection in commercial citrus: citrusinsider.org/Regulatory-Flyer
oSanta Barbara County Ag Commissioner's Office
- General ACP/HLB
oInformation on the state ACP/HLB program including maps, quarantine information, and a signup option for email alerts: citrusinsider.org/
oBiology of ACP and HLB, detection maps and recommendations for monitoring, eradication and management: ucanr.edu/sites/acp/
oUC IPM recommendations for ACP insecticides
oVideo on Best Practices in the Field, available in English and Spanish
oEn español -- Spanish-only ACP/HLB presentation video presentation and audio-only recording.
- Research
oLatest Science Advisory Panel Report
oUC Ag Experts Talk presentations on management of various citrus pests and diseases are available for viewing here and here on YouTube.
oCitrus Research Board video presentations from webinar series and California Citrus Conference
oSummaries of the latest research to combat HLB: ucanr.edu/sites/scienceforcitrushealth/
oScience-based analyses to guide policy decisions, logistics, and operations: www.datoc.us
-------- FOR MORE INFORMATION, CONTACT
Cressida Silvers
CA Citrus Pest and Disease Prevention Program
ACP/HLB Grower Liaison
Ventura, Santa Barbara and San Luis Obispo Counties
805 284-3310 (phone or text)
- Author: Kathy Keatley Garvey
If you missed UC Davis distinguished professor James R. Carey's well-attended seminar on "California's Fruit Fly Invasion: A 70-Year Struggle Nears Critical Mass," it's now online on YouTube.
His seminar, which took place June 3 in Briggs Hall, UC Davis, and on Zoom, drew global interest, stretching as far as Australia.
Carey pointed out that Callfornia has "the largest agricultural industry in the United States ($55 billion), is the fifth largest worldwide supplier of agricultural produces, grows more than 200 different crops, and "most fruit crops have been attacked by multiple tephritid species."
The California Department of Food and Agriculture (CDFA) reported that the first Mediterranean fruit fly (medfly) outbreak occurred on June 5, 1980, he said, and as of June 3, the state has detected 18 total species of fruit flies in 350 cities, amounting to 11,000 detections.
In his hour-long seminar, Carey presented an overview of the long-developing crisis, discussed lessons learned from analysis of fruit fly detection databases, and argued that "in order to have any chance at stemming this ever-rising tide, CDFA and the USDA urgently need to switch from their historic, ad hoc eradication strategy to a new one that is evidence-based and far more scientific."
In the closing moments, he asked "Why have oriental fruit fly outbreaks been occurring annually for the past 60 years in California?"
Because, he said, the fruit flies are "permanently established."
Carey, a 44-year member of the UC Davis faculty who is retiring in June, and a senior scholar in the Center for the Economics and Demography of Aging at UC Berkeley, researches insect biodemography, mortality dynamics, and insect invasion biology. He holds a doctorate in entomology from UC Berkeley (1980).
Carey served on the CDFA's Medfly Scientific Advisory Panel from 1987-1994, testified to the California Legislature "Committee of the Whole" in 1990 on the Medfly Crisis in California, and authored the paper "Establishment of the Mediterranean Fruit Fly in California" (1991, Science 258, 457).
He is a fellow of four professional societies: Entomological Society of America, the American Association for the Advancement of Science, the California Academy of Sciences, and the Gerontological Society of America. He is former director (2003-13) of a 11-university consortium funded by the National Institute on Aging (NIH/P01) on the evolutionary ecology of lifespan. He co-authored the book “Biodemography: An Introduction to Concepts and Methods” (Carey, J. R. and D. Roach. 2020; Princeton University Press) and authored the books, “Demography for Biologists (Oxford University Press 1993), Longevity (Princeton University Press, 2003), and Longevity Records: Life Spans of Mammals, Birds, Amphibians and Reptiles (Odense, 2000) as well as more than 250 journal articles and book chapters.
- Author: DIANA CERVANTES
La recolección de fresas, arándanos o cerezas, los paseos por rancherías para visitar cultivos de flores, la estancia en pequeños hoteles rurales e incluso las catas de vino son algunas de las actividades del agroturismo que muchos pequeños agricultores están incorporando a sus negocios.
El agroturismo, una tendencia en crecimiento en California, ofrece a los visitantes la oportunidad de experimentar la vida rural y agrícola de primera mano. Esta forma de turismo no solo brinda a los turistas una conexión más cercana con la naturaleza y la producción de alimentos, sino que también representa una fuente importante de ingresos adicionales para los agricultores locales.
Según el condado de San Diego, se estima que en esta región hay al menos 6,000 pequeñas granjas que podrían añadir el agroturismo a sus actividades diarias. Esta cifra refleja el enorme potencial que tiene el agroturismo para transformar la economía rural de la zona, proporcionando oportunidades de empleo y desarrollo sostenible.
Gracias a un financiamiento económico recibido a principios del 2024, los asesores de pequeñas granjas de la Extensión Cooperativa de la Universidad de California (UCCE) en San Diego se han dedicado a promover el amplio y variado abanico de actividades que los pequeños agricultores pueden integrar a sus negocios para aumentar su productividad.
“Nuestro propósito es unir a miembros de la comunidad que ya estén en el negocio del agroturismo o quieran comenzar a emprender su negocio, para ver que necesidades hay, y a que dificultades se enfrentan”, dijo Darlene Ruiz, asesora de la Extensión Cooperativa de la Universidad de California (UCCE) en San Diego.
En una junta de agroturismo realizada en los campos de flores de Carlsbad en San Diego, Ruiz explico que actualmente UCCE San Diego tiene un proyecto para crear una asociación entre las personas que ya están en el agroturismo y poder crear una conferencia sobre el tema el próximo año.
California, con su diversidad climática y geográfica, es un lugar ideal para el turismo agrícola. La implementación de esta actividad no solo beneficia a los agricultores al diversificar sus fuentes de ingresos, sino que también educa al público sobre la importancia de la agricultura local y sostenible.
Es gracias a un apoyo financiero que recibió UCCE San Diego para lanzar un proyecto en apoyo a la industria agroturística en San Diego que se estarán llevando a cabo juntas y paseo de campo para los productores locales.
“Tenemos una industria agrícola muy grande en San Diego, una industria turística que es bastante fuerte entonces la fusión de estas dos genera muchas oportunidades para que los productores puedan beneficiarse de actividades agroturísticas”, dijo Ramiro Lobo, asesor de la Extensión Cooperativa de la Universidad de California (UCCE) en San Diego.
En conclusión, el agroturismo en California ofrece una valiosa oportunidad tanto para los visitantes como para los agricultores. Con el apoyo de iniciativas como las de UCCE San Diego y el interés creciente en el turismo rural, esta tendencia promete enriquecer la economía local y fomentar una mayor apreciación por el mundo agrícola.
Para más información visite: https://ucanr.edu/blogs/agritourism/
Si desea contactar a alguno de los asesores de UCCE San Diego comuníquese al (858) 822-7711 o por email a relobo@ucdavis.edu
- Author: Ben A Faber
Update on Novel Ant Control Method in Citrus (MyAgLife in Citrus, Episode 828)
Recently, the Citrus Research Boards, IPM Entomologist, Ivan Milosavljevi?, Ph.D., was a guest on Episode 828 of MyAgLife in Citrus, where he provided an update on on a novel method of ant control in citrus. This method utilizes hydrogel beads filled with trace pesticide amounts.
To listen to the episode, please click below.
Episode 828 | April 30, 2024 | MyAgLife in Citrus – MyAgLife Daily News Report