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Congratulations to four outstanding young entomologists from the UC Davis Department of Entomology and Nematology--all PhDs to be.

They did UC Davis proud at the annual Entomological Society of America (ESA) meeting, which this year was a Joint Meeting of the Entomological Societies of America, Canada, and British Columbia. It took place Nov. 13-16 in Vancouver, British Columbia.

Doctoral candidates Danielle Rutkowski and Zachary Griebenow won the President's Prize or first-place honors for their individual research presentations. This was Rutkowski's second consecutive President's Prize. 

Doctoral candidate Lindsey Mack and doctoral student Adelaine “Addie” Abrams scored runner-up or second-place for their research presentations in the highly competitive program. 

Their topics ranged from bumble bees (Rutkowski) and ants (Griebenow) to mosquitoes (Mack) and thrips and aphids (Abrams). 

At the ESA annual meetings, students are offered the opportunity to present their research and win prizes. They can compete in 10-minute papers (oral), posters, or infographics. The President's Prize winners receive a one-year paid membership in ESA, a $75 cash prize, and a certificate. Second-winners score a one-year free membership in ESA and a certificate. 

Danielle Rutkowski 
Danielle Rutkowski, who studies with community ecologists Rachel Vannette, associate professor, and distinguished professor Richard “Rick” Karban, spoke on “The Mechanism Behind Beneficial Effects of Bee-Associated Fungi on Bumble Bee Health,” at her presentation in the category, Graduate School Plant-Insect Ecosytems: Pollinators.

Her abstract: "Bees often interact with fungi, including at flowers and within bee nests. We have previously found that supplementing bumble bee colonies with these bee-associated fungi improves bee survival and increases reproductive output, but the mechanisms behind these effects are unclear. This research aimed to determine the mechanisms underlying positive impacts of fungal supplementation in the bumble bee, Bombus impatiens. We tested two hypotheses regarding possible nutritional benefits provided by bee-associated fungi. These included the role of fungi as a direct food source to bees, and the production of nutritionally important metabolites by fungi. To test these mechanisms, we created microcolonies bumble bees and exposed each microcolony to one of four treatment groups. These four treatments were created based on the presence of fungal cells and the presence of fungal metabolites. We found that bee survival and reproduction were unaffected by treatment, with trends of decreased survival and reproduction when fungi were present. This contradicts previous results we've found using this bumble bee species, where fungi had a positive impact. It is possible that this disparity in results is due to differences in pathogen pressure between the two experiments, as bees in the first experiment were exposed to large amounts of pathogen through provided pollen, including Ascosphaera and Aspergillus. This pollen was sterilized for subsequent experiments, reducing pathogen load. Therefore, it is possible that bee-associated fungi benefit bees through pathogen inhibition, and future work exploring this hypothesis is necessary to fully understand the role of these fungi in bumble bee health."

Zachary Griebenow
Zach Griebenow, who studies with major professor and ant specialist Phil Ward, (Griebenow also captained the UC Davis Entomology Games Team in its national championship win at the Entomology Games or Bug Bowl) explained  “Systematic Revision of the Obscure Ant Subfamily Leptanillinae (Hymenoptera: Formicidae), Reciprocally Informed by Phylogenomic Inference and Morphological Data.” His category: Graduate School Systematics, Evolution and Biodiversity: Evolution 1. 

His abstract: "Ants belonging to the subfamily Leptanillinae (Hymenoptera: Formicidae) are sister to nearly all other extant ants. Miniscule and subterranean, little is known of their behavior. Contrary to the collecting bias observed in most ants, male leptanilline specimens are acquired more easily than workers or queens. The sexes are almost never collected in association, and many subclades within the Leptanillinae are known from male specimens only. Our comprehension of evolutionary relationships among the Leptanillinae is further obstructed by oft-bizarre derivation in male phenotypes that are too disparate for phylogeny to be intuited from morphology alone. These restrictions plague our understanding of the Leptanillinae with probable taxonomic redundancy. My thesis aims at leptanilline taxonomy that reflects phylogeny, inferred from both genotype and phenotype, and integrates morphological data from both sexes. Here I present the results of (1) phylogenomic inference from ultra-conserved elements (UCEs), compensating for potential systematic biases in these data, representing 63 terminals; and (2) Bayesian total-evidence inferences from a handful of loci, jointly with discrete male morphological characters coded in binary non-additive or multistate fashion. Notably, these analyses identify worker specimens belonging to the genera Noonilla and Yavnella, which were heretofore known only from males. Given such discoveries across the Leptanillinae, the number of valid leptanilline genera is reduced from seven to three in order to create a genus-level classification that upholds monophyly along with diagnostic utility." 

Lindsey Mack
Mack, who studies with medical entomologist-geneticist Geoffrey Attardo, assistant professor, covered “Three Dimensional Analysis of Vitellogenesis in Aedes aegypi Using Synchrotron X-Ray MicroCT” in the category, Graduate School Physiology, Biochemistry and Toxicology: Physiology. 

Her abstract: "Traditional methods of viewing the internal anatomy of insects require some degree of tissue manipulation and/or destruction. Using synchrotron-based x-ray phase contrast microCT (pcMicroCT) avoids this issue and has the capability to produce high contrast, three dimensional images. Our lab is using this technique to study the morphological changes occurring in the mosquito Aedes aegypti during its reproductive cycle. Ae. aegypti is the primary global arbovirus vector, present on all continents except Antarctica. Their ability to spread these viruses is tightly linked with their ability to reproduce, as the production of eggs in this species is initiated by blood feeding. Amazingly, this species produces a full cohort of eggs (typically 50-100) in just 3 days' time following a blood meal. This rapid development represents dramatic shifts in physiological processes that result in massive volumetric changes to internal anatomy over time. To explore these changes thoroughly, a time course of microCT scans were completed over the vitellogenic period. This dataset provides a virtual representation of the volumetric, conformational, and positional changes occurring in tissues important for reproduction across the vitellogenic period. This dataset provides the field of vector biology with a detailed three-dimensional internal atlas of the processes of vitellogenesis in Ae. aegypti."

Addie Abrams
Abrams, who studies with Extension agricultural entomologist and assistant professor Ian Grettenberger (she is a member of the Horticulture and Agronomy Graduate Group), titled her research, “Hitting the Mark: Precision Pesticide Applications for the Control of Aphids in California Lettuce" in the category, Graduate School Physiology, Biochemistry and Toxicology: Integrated Pest Management. 

Her abstract: "Commercial lettuce production in California's central coast represents 70 percent of the production in the United States. Recent discoveries of some chemistries in ground and surface water in the Salinas valley region have placed the insecticidal chemistries used by the industry at risk of increased regulation. Automated thinner-sprayers use plant-detection sensors to apply chemical sprays directly to individual lettuce plants, so that the same amount of product to plants as a standard broadcast sprayer while potentially reducing the amount of pesticide applied per acre by up to 90 percent. Field experiments testing this technology for the control of western flower thrips (Frankliniella occidentalis) and aphids, lettuce-currant aphid (Nasovonia ribisnigri) and others, were conducted to compare the efficacy of automated sprays to a conventional broadcast application system. Experiments were conducted in conventionally managed organic romaine lettuce fields using a complete randomized block design. Prior to and at regular intervals after treatment, heads were sampled from experimental and control plots to assess pest pressure. Results from this experiment validate the use of the automated sprayers to apply insecticides for the control of aphid and thrips pests in lettuce and will be discussed in the context of developing best-use-practices for this technology."

The 7000-member ESA, founded in 1889, is the largest organization in the world serving the professional and scientific needs of entomologists and individuals in related disciplines. Its members,  affiliated with educational institutions, health agencies, private industry, and government, are researchers, teachers, extension service personnel, administrators, marketing representatives, research technicians, consultants, students, pest management professionals, and hobbyists.

(See all of student competition winners on ESA site)

Doctoral candidates Danielle Rutkowski and Zachary Griebenow of the UC Davis Department of Entomology and Nematology won the President's Prize or first-place honors for their individual research presentations at the 2022 Joint  Meeting of the Entomological Societies of America, Canada, and British Columbia, held Nov. 13-16 in Vancouver, British Columbia.

This was Rutkowski's second consecutive President's Prize. 

Doctoral candidate Lindsey Mack and doctoral student Adelaine “Addie” Abrams scored second-place for their research presentations in the highly competitive program. 

Their topics ranged from bumble bees (Rutkowski) and ants (Griebenow) to mosquitoes (Mack) and thrips and aphids (Abrams). 

At the Entomological Society of America (ESA) annual meetings, students are offered the opportunity to present their research and win prizes. They can compete in 10-minute papers (oral), posters, or infographics. The President's Prize winners receive a one-year paid membership in ESA, a $75 cash prize, and a certificate. Second-winners score a one-year free membership in ESA and a certificate. 

Danielle Rutkowski 
Danielle Rutkowski, who studies with community ecologists Rachel Vannette, associate professor, and distinguished professor Richard “Rick” Karban, spoke on “The Mechanism Behind Beneficial Effects of Bee-Associated Fungi on Bumble Bee Health,” at her presentation in the category, Graduate School Plant-Insect Ecosytems: Pollinators.

Her abstract: "Bees often interact with fungi, including at flowers and within bee nests. We have previously found that supplementing bumble bee colonies with these bee-associated fungi improves bee survival and increases reproductive output, but the mechanisms behind these effects are unclear. This research aimed to determine the mechanisms underlying positive impacts of fungal supplementation in the bumble bee, Bombus impatiens. We tested two hypotheses regarding possible nutritional benefits provided by bee-associated fungi. These included the role of fungi as a direct food source to bees, and the production of nutritionally important metabolites by fungi. To test these mechanisms, we created microcolonies bumble bees and exposed each microcolony to one of four treatment groups. These four treatments were created based on the presence of fungal cells and the presence of fungal metabolites. We found that bee survival and reproduction were unaffected by treatment, with trends of decreased survival and reproduction when fungi were present. This contradicts previous results we've found using this bumble bee species, where fungi had a positive impact. It is possible that this disparity in results is due to differences in pathogen pressure between the two experiments, as bees in the first experiment were exposed to large amounts of pathogen through provided pollen, including Ascosphaera and Aspergillus. This pollen was sterilized for subsequent experiments, reducing pathogen load. Therefore, it is possible that bee-associated fungi benefit bees through pathogen inhibition, and future work exploring this hypothesis is necessary to fully understand the role of these fungi in bumble bee health."

Zachary Griebenow
Zach Griebenow, who studies with major professor and ant specialist Phil Ward, (Griebenow also captained the UC Davis Entomology Games Team in its national championship win at the Entomology Games or Bug Bowl) explained  “Systematic Revision of the Obscure Ant Subfamily Leptanillinae (Hymenoptera: Formicidae), Reciprocally Informed by Phylogenomic Inference and Morphological Data.” His category: Graduate School Systematics, Evolution and Biodiversity: Evolution 1.

His abstract: "Ants belonging to the subfamily Leptanillinae (Hymenoptera: Formicidae) are sister to nearly all other extant ants. Miniscule and subterranean, little is known of their behavior. Contrary to the collecting bias observed in most ants, male leptanilline specimens are acquired more easily than workers or queens. The sexes are almost never collected in association, and many subclades within the Leptanillinae are known from male specimens only. Our comprehension of evolutionary relationships among the Leptanillinae is further obstructed by oft-bizarre derivation in male phenotypes that are too disparate for phylogeny to be intuited from morphology alone. These restrictions plague our understanding of the Leptanillinae with probable taxonomic redundancy. My thesis aims at leptanilline taxonomy that reflects phylogeny, inferred from both genotype and phenotype, and integrates morphological data from both sexes. Here I present the results of (1) phylogenomic inference from ultra-conserved elements (UCEs), compensating for potential systematic biases in these data, representing 63 terminals; and (2) Bayesian total-evidence inferences from a handful of loci, jointly with discrete male morphological characters coded in binary non-additive or multistate fashion. Notably, these analyses identify worker specimens belonging to the genera Noonilla and Yavnella, which were heretofore known only from males. Given such discoveries across the Leptanillinae, the number of valid leptanilline genera is reduced from seven to three in order to create a genus-level classification that upholds monophyly along with diagnostic utility." 

Lindsey Mack
Mack, who studies with medical entomologist-geneticist Geoffrey Attardo, assistant professor, covered “Three Dimensional Analysis of Vitellogenesis in Aedes aegypi Using Synchrotron X-Ray MicroCT” in the category, Graduate School Physiology, Biochemistry and Toxicology: Physiology.

Her abstract: "Traditional methods of viewing the internal anatomy of insects require some degree of tissue manipulation and/or destruction. Using synchrotron-based x-ray phase contrast microCT (pcMicroCT) avoids this issue and has the capability to produce high contrast, three dimensional images. Our lab is using this technique to study the morphological changes occurring in the mosquito Aedes aegypti during its reproductive cycle. Ae. aegypti is the primary global arbovirus vector, present on all continents except Antarctica. Their ability to spread these viruses is tightly linked with their ability to reproduce, as the production of eggs in this species is initiated by blood feeding. Amazingly, this species produces a full cohort of eggs (typically 50-100) in just 3 days' time following a blood meal. This rapid development represents dramatic shifts in physiological processes that result in massive volumetric changes to internal anatomy over time. To explore these changes thoroughly, a time course of microCT scans were completed over the vitellogenic period. This dataset provides a virtual representation of the volumetric, conformational, and positional changes occurring in tissues important for reproduction across the vitellogenic period. This dataset provides the field of vector biology with a detailed three-dimensional internal atlas of the processes of vitellogenesis in Ae. aegypti."

Addie Abrams
Abrams, who studies with Extension agricultural entomologist and assistant professor Ian Grettenberger (she is a member of the Horticulture and Agronomy Graduate Group), titled her research, “Hitting the Mark: Precision Pesticide Applications for the Control of Aphids in California Lettuce" in the category, Graduate School Physiology, Biochemistry and Toxicology: Integrated Pest Management.

Her abstract: "Commercial lettuce production in California's central coast represents 70 percent of the production in the United States. Recent discoveries of some chemistries in ground and surface water in the Salinas valley region have placed the insecticidal chemistries used by the industry at risk of increased regulation. Automated thinner-sprayers use plant-detection sensors to apply chemical sprays directly to individual lettuce plants, so that the same amount of product to plants as a standard broadcast sprayer while potentially reducing the amount of pesticide applied per acre by up to 90 percent. Field experiments testing this technology for the control of western flower thrips (Frankliniella occidentalis) and aphids, lettuce-currant aphid (Nasovonia ribisnigri) and others, were conducted to compare the efficacy of automated sprays to a conventional broadcast application system. Experiments were conducted in conventionally managed organic romaine lettuce fields using a complete randomized block design. Prior to and at regular intervals after treatment, heads were sampled from experimental and control plots to assess pest pressure. Results from this experiment validate the use of the automated sprayers to apply insecticides for the control of aphid and thrips pests in lettuce and will be discussed in the context of developing best-use-practices for this technology."

The 7000-member ESA, founded in 1889, is the largest organization in the world serving the professional and scientific needs of entomologists and individuals in related disciplines. Its members,  affiliated with educational institutions, health agencies, private industry, and government, are researchers, teachers, extension service personnel, administrators, marketing representatives, research technicians, consultants, students, pest management professionals, and hobbyists.

(See all of student competition winners on ESA site)

In 2022, I estimate rice acreage in the Delta, south of the Yolo Bypass, was at least 8,000 acres. Most Delta rice is grown in San Joaquin County, but there is some acreage in Sacramento County. While Delta rice acreage is relatively small compared to that in the Sacramento Valley, it has been steadily increasing over the last several years (Table 1).

 

Given the increasing interest in rice production among Delta growers, and the differences in production practices from the Sacramento Valley, UC Cooperative Extension and UC Davis will be releasing a cost of production report specifically for Delta rice later this year or in early 2023. A Delta rice cost study was last produced in 2007, so updating the study was long-overdue. I want to thank all the growers who participated in a focus group to update the study.

Cool temperatures can make the Delta a challenging place to grow rice. Low night-time temperatures can cause blanking, which results in empty grains. Growers are limited to using only very-early and early maturing varieties. Most of the Delta acreage was planted with variety M-206, but some growers also planted a portion of their acreage with M-105. In 2022, we continued the UCCE Delta variety trial, which will help to identify and advance cold-tolerant varieties. The Delta trial is part of a statewide network of trials, led by UC Rice Extension Specialist, Bruce Linquist, and coordinated by Staff Researcher, Ray Stogsdill. I anticipate that the statewide results will be ready in time for the February Field Notes newsletter.

This year, I worked with growers and consultants on a handful of pests. Weed management is always top-of-mind for rice growers. There are limited practices and products that can control problematic weeds, and in some circumstances, the weeds may develop resistance to the herbicides that are available. If herbicide resistance is suspected, please contact me so that we can submit weed seeds for testing. We would collect the seeds in the late summer or early fall when they have matured but have not shattered. Resistance testing is overseen by UC Weed Science Extension Specialist, Kassim Al-Khatib, and takes place in greenhouses during the winter. By the following spring, we provide the grower with information on which herbicides are still working and which are not.

Over the last several years, I have conducted trials to evaluate the efficacy of a new herbicide product, Loyant (florpyrauxifen-benzyl; Corteva Agriscience), on grasses and sedges in the Delta drill-seeded system. (See https://ucanr.edu/sites/deltacrops/files/361256.pdf for project reports.) Loyant is now registered and will be available for the 2023 season. This year, I collaborated with graduate student, Deniz Inci, and Kassim Al-Khatib to evaluate product efficacy on cattails. With only one year of data, we cannot make too many conclusions, but it appeared that Loyant had efficacy on small cattails (less than three feet tall, Figure 1). The results were promising, and we will continue our investigation next year to see what more we can learn.

I have been trapping armyworms in the Delta since 2016 (Figure 2), in collaboration with fellow farm advisor, Luis Espino. The traps catch true armyworm moths. They were deployed on three ranches and monitored weekly. In 2022, we recovered the highest moth counts since 2017, and the peak flight occurred about one week earlier than in 2017. This is important information for management because, based on the armyworm life cycle, we know that peak worm populations occur approximately two weeks after peak moth flight. In other words, growers can make informed decisions based on the monitoring data and adapt their management to the field conditions. Trap monitoring is one part of an integrated pest management program for armyworms, which also includes scouting for feeding damage and the worms themselves. Over the years, I have observed armyworms in riparian and wetland vegetation that neighbor rice fields, so it is important to scout those areas, too. More information about Delta armyworm trapping is available on my website (https://ucanr.edu/sites/deltacrops/Rice/Armyworms/).

I observed a couple important diseases this year – stem rot and rice blast. In recent years, we have observed stem rot on certain ranches at harvest. As fields were getting drained, the plants turned brown instead of golden, and grains hadn't filled (Figure 3). We developed post-harvest straw management programs that included burying the residue to try to break down the fungal inoculum. This year, we noticed the problem in some locations early enough to make treatment decisions. We walked the fields at late-tillering and early-heading and found black lesions on the stems at the water line (Figure 4). We submitted samples to UC Plant Pathology Extension Specialist, Cassandra Swett, and confirmed stem rot. Treatment timing is critical for managing stem rot, and treatment at early-heading has been observed to be most effective. There is a tendency for stem rot to be more severe on low potassium soils, and many Delta soils are naturally low in potassium. A potassium fertility program may help mitigate disease severity, but management should include a multi-pronged approach that also includes post-harvest straw management and possibly fungicide applications. Currently, there is no varietal resistance to the disease. The rice blast that was confirmed was in one field. We observed lesions below the panicle (“neck blast”) that caused blanking. Blast spores can move by air, are favored by warm, wet conditions, and can be exacerbated by excess nitrogen. Fungicides are registered and are most effective at early-heading. For more information on both of these diseases, see the fact sheets written by Luis Espino (https://rice.ucanr.edu/FactSheets/Rice/), or give me a call.

We should continue to keep weedy rice on our radars because we have seen it in the Delta in the past. Where we have observed light infestations, it appears that keen management – including in-season rogueing, post-harvest management that includes straw chopping but not incorporation, and winter flooding – can reduce, if not eliminate the pest. These are our management tools until a herbicide is approved for spot-spraying. Growers should also pay attention to equipment sanitation – harvesting weedy rice fields last (if possible) and thoroughly cleaning out equipment after harvesting fields where weedy rice has been observed.

Finally, I will be starting new projects this winter, in collaboration with fellow farm advisor, Whitney Brim-DeForest, and graduate student, Sara Rosenberg, to evaluate winter cover cropping between rice crops. Our objectives are to evaluate carbon and nitrogen cycling and variety survivability during the cool, wet (we hope!) winter conditions. These projects are supported by the CDFA Healthy Soils Program and the CA Rice Research Board. I look forward to sharing results in the years to come.

I am grateful to work with a great team of UC colleagues on these rice projects. I am also grateful for all the growers who have collaborated with us. I wish everyone a good end to the year, and I look forward to working with you again in 2023.

*  *  *

Michelle Leinfelder-Miles is the UC Cooperative Extension Delta Crops Resource Management Advisor serving San Joaquin, Contra Costa, Sacramento, Solano, and Yolo counties.

 

Original source: Rice Notes -- November 2022 newsletter