- (Focus Area) Agriculture
- Author: Kathy Keatley Garvey
In the sweltering heat of Solano County (100 degrees) during National Pollinator Month, how about an image of a sweat bee, genus Halictus, a tiny bee that's often overlooked in the world of pollinators.
It's a social bee that nests in the soil. "These nests consist of a complex of tunnels with individual brood chambers," according to California Bees and Blooms: A Guide for Gardeners and Naturalists (Heyday), the work of UC-affiliated scientists,
My camera caught this Halictus flying over Coreopsis in our Vacaville pollinator garden on June 5.
Camera: Nikon Z8 with a 50mm lens
Settings: Shutter speed, 1/4000 of a second; f-stop, 5; ISO 500.
UC Davis distinguished professor emerita Lynn Kimsey, emeritus director of the Bohart Museum of Entomology, and Bohart Museum scientist Sandy Shanks said the species appears to be Halictus ligatus.
Most Halictus species are generalist foragers, according to the Great Sunflower Project. "They use all sorts of genera of plants from the Asteraceae to Scrophulariaceae. They are very common on composites (daisy-like disc and ray flowers) in summer and fall."
We've seen them on everything from mustard to milkweeds to catmint to rock purslane, from spring to fall. They also appear regularly on the tower of jewels (Echium wildpretii).
Not to mention the Coreopsis.
/span>- Author: Jeffrey P Mitchell
In an effort to extend information on CASI's twenty-year conservation agriculture study that has been conducted at the University field station in Five Points, CA and that has been recently published in the journal, California Agriculture, Jeff Mitchell provided three radio interviews on the morning Ag Report that Don York produces for KMJ580 AM each morning out of Fresno. The segments aired on May 23rd and on June 4th and 6th, 2024 and are available below. Mitchell shared findings of the long-term “NRI Project” that since 1998 has examined four production systems – standard tillage without cover crop, standard tillage with cover crop, no-till without cover crop, and no-till with cover crop.
The NRI Project started as an effort to determine the potential of reduced disturbance tillage in terms of generating or producing less dust and in the early 2000s found that dust can be significantly reduced by as much as 80% with a variety of reduced tillage practices relative to standard tillage techniques that have been widely used in annual crop fields throughout the San Joaquin Valley since the early 1930s. The recent findings from the unique long-term study have shown that several soil health indicators including aggregation, water infiltration, biodiversity, and surface carbon were improved through the long-term use of cover crops with reduced disturbance tillage.
In the interviews, Mitchell points out that the systems that were evaluated and developed in the NRI Project were not at all easy to implement and required considerable trial-and-error effort to achieve. Yields, for instance, of cotton in the early years under the high residue, no-till cover crop system lagged behind the standard tillage, however once effective planting techniques were learned to establish the cotton crop. There were no yield differences between the two tillage systems for the next several years.
The results of this study that included 18 coauthors can be seen at https://doi.org/10.3733/001c.94714
Jeff Mitchell on KMJ Ag Report 5-23-24
Jeff Mitchell on KMJ Ag Report 6-4-24
Jeff Mitchell on KMJ Ag Report 6-6-24
- Author: Ben A Faber
Movento (spirotetramet) has been renewed for use on citrus Asian citrus psyllid in California. It's a foliar spray that is systemic especially moving to new tissue where ACP feeds. It also controls some other pests, such as thrips and leafminer. It has a short persistence effect on natural enemies and has low toxicity issues.
As an interesting aside, I just learned that cryolite (Kryocide, Pro-Kil) which was considered for organic registration at one time, has lost its registration. It was a stomach poison that worked on leaf-feeding beetles and lepidopteran pests like orange tortrix. The high level of fluoride necessitated its loss of registration.
- 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)