The benefits of nature exposure: The need for research that better informs implementation.

Concern about humanity's detachment from nature has spawned a global push to increase the availability of green spaces within cities. One impetus for this movement is a growing collection of studies documenting an association between improved human well-being and exposure to nature. The challenge lies in translating this research into pragmatic recommendations for cities. The usefulness of the existing research portfolio is diminished by the limitations of prevailing research designs. For example, most nature exposure studies (>80%) are observational. The rare randomized manipulative experiments tend to be indoors or virtual and rely on nature exposures on the order of ten to fifteen minutes. "Nature" and "biodiversity" are commonly invoked together as benefiting human well-being despite little evidence that biodiversity has particular importance for human psychological and emotional health. The most glaring gap in nature exposure research is the neglect of differences among cultures and ethnic groups with respect to the nature they prefer. In the few cases where researchers looked for differences among groups, they often found heterogeneous responses. Finally, few studies have compared greening interventions to other possible efforts to improve urban life. Thus, the utopian city of the future might be resplendent with urban parks on every block, but it is not clear whether those parks should offer basketball and pickleball courts, or small woodlands with a cornucopia of birds. We advocate for the next generation of nature exposure research that better informs the envisioning of our future sustainable cities with enhanced and equitable access to nature.

Longitudinal Transcriptomic, Proteomic, and Metabolomic Response of Citrus sinensis to Diaphorina citri Inoculation of Candidatus Liberibacter asiaticus.

Huanglongbing (HLB) is a fatal citrus disease that is currently threatening citrus varieties worldwide. One putative causative agent, Candidatus Liberibacter asiaticus (CLas), is vectored by Diaphorina citri, known as the Asian citrus psyllid (ACP). Understanding the details of CLas infection in HLB disease has been hindered by its Candidatus nature and the inability to confidently detect it in diseased trees during the asymptomatic stage. To identify early changes in citrus metabolism in response to inoculation of CLas using its natural psyllid vector, leaves from Madam Vinous sweet orange (Citrus sinensis (L.) Osbeck) trees were exposed to CLas-positive ACP or CLas-negative ACP and longitudinally analyzed using transcriptomics (RNA sequencing), proteomics (liquid chromatography-tandem mass spectrometry; data available in Dryad: 10.25338/B83H1Z), and metabolomics (proton nuclear magnetic resonance). At 4 weeks postexposure (wpe) to psyllids, the initial HLB plant response was primarily to the ACP and, to a lesser extent, the presence or absence of CLas. Additionally, analysis of 4, 8, 12, and 16 wpe identified 17 genes and one protein as consistently differentially expressed between leaves exposed to CLas-positive ACP versus CLas-negative ACP. This study informs identification of early detection molecular targets and contributes to a broader understanding of vector-transmitted plant pathogen interactions.

Co-action of COP1, SPA and cryptochrome in light signal transduction and photomorphogenesis of the moss Physcomitrium patens.

The Arabidopsis COP1/SPA ubiquitin ligase suppresses photomorphogenesis in darkness. In the light, photoreceptors inactivate COP1/SPA to allow a light response. While SPA genes are specific to the green lineage, COP1 also exists in humans. This raises the question of when in evolution plant COP1 acquired the need for SPA accessory proteins. We addressed this question by generating Physcomitrium Ppcop1 mutants and comparing their visible and molecular phenotypes with those of Physcomitrium Ppspa mutants. The phenotype of Ppcop1 nonuple mutants resembles that of Ppspa mutants. Most importantly, both mutants produce green chloroplasts in complete darkness. They also exhibit dwarfed gametophores, disturbed branching of protonemata and absent gravitropism. RNA-sequencing analysis indicates that both mutants undergo weak constitutive light signaling in darkness. PpCOP1 and PpSPA proteins form a complex and they interact via their WD repeat domains with the VP motif of the cryptochrome CCE domain in a blue light-dependent manner. This resembles the interaction of Arabidopsis SPA proteins with Arabidopsis CRY1, and is different from that with Arabidopsis CRY2. Taken together, the data indicate that PpCOP1 and PpSPA act together to regulate growth and development of Physcomitrium. However, in contrast to their Arabidopsis orthologs, PpCOP1 and PpSPA proteins execute only partial suppression of light signaling in darkness. Hence, additional repressors may exist that contribute to the repression of a light response in dark-exposed Physcomitrium.

The pentatricopeptide repeat protein DG1 promotes the transition to bilateral symmetry during Arabidopsis embryogenesis through GUN1-mediated plastid signals.

During Arabidopsis embryogenesis, the transition of the embryo's symmetry from radial to bilateral between the globular and heart stage is a crucial event, involving the formation of cotyledon primordia and concurrently the establishment of a shoot apical meristem (SAM). However, a coherent framework of how this transition is achieved remains to be elucidated. In this study, we investigated the function of DELAYED GREENING 1 (DG1) in Arabidopsis embryogenesis using a newly identified dg1-3 mutant. The absence of chloroplast-localized DG1 in the mutants led to embryos being arrested at the globular or heart stage, accompanied by an expansion of WUSCHEL (WUS) and SHOOT MERISTEMLESS (STM) expression. This finding pinpoints the essential role of DG1 in regulating the transition to bilateral symmetry. Furthermore, we showed that this regulation of DG1 may not depend on its role in plastid RNA editing. Nevertheless, we demonstrated that the DG1 function in establishing bilateral symmetry is genetically mediated by GENOMES UNCOUPLED 1 (GUN1), which represses the transition process in dg1-3 embryos. Collectively, our results reveal that DG1 functionally antagonizes GUN1 to promote the transition of the Arabidopsis embryo's symmetry from radial to bilateral and highlight the role of plastid signals in regulating pattern formation during plant embryogenesis.

Study on the citrus greening disease: Current challenges and novel therapies.

The unprecedented worldwide spread of the Citrus greening disorder, called Huanglongbing (HLB), has urged researchers for rapid interventions. HLB poses a considerable threat to global citriculture owing to its devastating impact on citrus species. This disease is caused by Candidatus Liberibacter species (CLs), primarily transferred through psyllid insects, such as Trioza erytreae and Diaphorina citri. It results in phloem malfunction, root decline, and altered plant source-sink relationships, leading to a deficient plant with minimal yield before it dies. Thus, many various techniques have been employed to eliminate HLB and control vector populations through the application of insecticides and antimicrobials. The latter have evidenced short-term efficiency. While nucleic acid-based analyses and symptom-based identification of the disease have been used for detection, they suffer from limitations such as false negatives, complex sample preparation, and high costs. To address these challenges, secreted protein-based biomarkers offer a promising solution for accurate, rapid, and cost-effective disease detection. This paper presents an overview of HLB symptoms in citrus plants, including leaf and fruit symptoms, as well as whole tree symptoms. The differentiation between HLB symptoms and those of nutrient deficiencies is discussed, emphasizing the importance of precise identification for effective disease management. The elusive nature of CLs and the challenges in culturing them in axenic cultures have hindered the understanding of their pathogenic mechanisms. However, genome sequencing has provided insights into CLs strains' metabolic traits and potential virulence factors. Efforts to identify potential host target genes for resistance are discussed, and a high-throughput antimicrobial testing method using Citrus hairy roots is introduced as a promising tool for rapid assessment of potential treatments. This review summarizes current challenges and novel therapies for HLB disease. It highlights the urgency of developing accurate and efficient detection methods and identifying the complex relations between CLs and their host plants. Transgenic citrus in conjunction with secreted protein-based biomarkers and innovative testing methodologies could revolutionize HLB management strategies toward achieving a sustainable citrus cultivation. It offers more reliable and practical solutions to combat this devastating disease and safeguard the global citriculture industry.

A Life Cycle Assessment of Reusable and Disposable Surgical Caps.

INTRODUCTION: Surgical cap attire plays an important role in creating a safe and sterile environment in procedural suites, thus the choice of reusable versus disposable caps has become an issue of much debate. Given the lack of evidence for differences in surgical site infection (SSI) risk between the two, selecting the cap option with a lower carbon footprint may reduce the environmental impact of surgical procedures. However, many institutions continue to recommend the use of disposable bouffant caps. METHODS: ISO-14044 guidelines were used to complete a process-based life cycle assessment to compare the environmental impact of disposable bouffant caps and reusable cotton caps, specifically focusing on CO2 equivalent (CO2e) emissions, water use and health impacts. RESULTS: Reusable cotton caps reduced CO2e emissions by 79% when compared to disposable bouffant caps (10 kg versus 49 kg CO2e) under the base model scenario with a similar reduction seen in disability-adjusted life years. However, cotton caps were found to be more water intensive than bouffant caps (67.56 L versus 12.66 L) with the majority of water use secondary to production or manufacturing. CONCLUSIONS: Reusable cotton caps have lower total lifetime CO2e emissions compared to disposable bouffant caps across multiple use scenarios. Given the lack of evidence suggesting a superior choice for surgical site infection prevention, guidelines should recommend reusable cotton caps to reduce the environmental impact of surgical procedures.

Linking the macroclimatic niche of native lithophytic ferns and their prevalence in urban environments.

PREMISE: Vertical surfaces in urban environments represent a potential expansion of niche space for lithophytic fern species. There are, however, few records of differential success rates of fern species in urban environments. METHODS: The occurrence rates of 16 lithophytic fern species native to the northeastern USA in 14 biomes, including four urban environments differentiated by percentage of impervious surfaces, were evaluated. In addition, the natural macroclimatic ranges of these species were analyzed to test whether significant differences existed in climatic tolerance between species that occur in urban environments and species that do not. RESULTS: Three species appear to preferentially occur in urban environments, two species may facultatively occur in urban environments, and the remaining 11 species preferentially occur in nondeveloped rural environments. The natural range of fern species that occur in urban environments had higher summer temperatures than the range of species that do not, whereas other macroclimatic variables, notably winter temperatures and precipitation, were less important or insignificant. CONCLUSIONS: Vertical surfaces in urban environments may represent novel niche space for some native lithophytic fern species in northeastern USA. However, success in this environment depends, in part, on tolerance of the urban heat island effect, especially heating of impervious surfaces in summer.

Designing cities for everyday nature.

The motivations for incorporating nature into the design of cities have never been more compelling. Creating experiences with nature that occur every day (everyday nature) in cities could help reverse the fate of many threatened species and connect people with nature and living cultural traditions. However, this requires more than just urban greening; it involves ensuring daily doses of nature in a way that also supports nonhuman organisms. A major shift in the way nature is conceived of and is made part of the design of cities is required. Principles include reconsidering nature as a development opportunity rather than a constraint and eliminating offsetting of biodiversity site values. Processes include using biodiversity-sensitive design frameworks and establishing meaningful professional engagement among ecologists, planners, and designers. Challenges include design obstacles, conflicts between nature and people (e.g., safety, disease, and noise) that require careful management, and socioeconomic and political considerations (e.g., Global North vs. Global South). Research to interrogate the multiple benefits of nature in cities can complement experimental interventions, ultimately supporting better urban design and creating much more resiliently built environments for people and nature.

Diseño de ciudades para la naturaleza cotidiana Resumen Los motivos para incorporar a la naturaleza dentro del diseño urbano jamás habían sido tan convincentes. La creación en las ciudades de experiencias con la naturaleza que ocurren a diario (naturaleza cotidiana) podría ayudar a cambiar el destino de muchas especies amenazadas y conectar a las personas con la naturaleza y las tradiciones culturales vivientes. Lo anterior requiere más que reverdecimiento urbano ya que involucra dosis diarias de naturaleza de manera que también mantengan a los organismos no humanos. Se necesita de un cambio mayor en la manera en la que se concibe a la naturaleza y cómo se le hace parte del diseño urbano. Los principios incluyen reconsiderar a la naturaleza como una oportunidad de desarrollo en lugar de una limitación y eliminar la compensación del valor de los sitios de biodiversidad. Los procesos incluyen el uso de marcos de diseños sensibles con la biodiversidad y el establecimiento de una participación profesional significativa entre los ecologistas, los planeadores y los diseñadores. Los retos incluyen los obstáculos del diseño, conflictos entre la naturaleza y las personas (seguridad, enfermedades y ruido) que requieren de un manejo cuidadoso y consideraciones políticas (Norte Global versus Sur Global). La investigación para interrogar los múltiples beneficios de la naturaleza en las ciudades puede complementar a las intervenciones, a la larga respaldando un mejor diseño urbano y creando ambientes para las personas y la naturaleza construidos con mayor resiliencia.

High-Resolution Modeling of Summertime Biogenic Isoprene Emissions in New York City.

As cities strive for ambitious increases in tree canopy cover and reductions in anthropogenic volatile organic compound (AVOC) emissions, accurate assessments of the impacts of biogenic VOCs (BVOCs) on air quality become more important. In this study, we aim to quantify the impact of future urban greening on ozone production. BVOC emissions in dense urban areas are often coarsely represented in regional models. We set up a high-resolution (30 m) MEGAN (The Model of Emissions of Gases and Aerosols from Nature version 3.2) to estimate summertime biogenic isoprene emissions in the New York City metro area (NYC-MEGAN). Coupling an observation-constrained box model with NYC-MEGAN isoprene emissions successfully reproduced the observed isoprene concentrations in the city core. We then estimated future isoprene emissions from likely urban greening scenarios and evaluated the potential impact on future ozone production. NYC-MEGAN predicts up to twice as much isoprene emissions in NYC as the coarse-resolution (1.33 km) Biogenic Emission Inventory System version 3.61 (BEIS) on hot summer days. We find that BVOCs drive ozone production on hot summer days, even in the city core, despite large AVOC emissions. If high isoprene emitting species (e.g., oak trees) are planted, future isoprene emissions could increase by 1.4-2.2 times in the city core, which would result in 8-19 ppbv increases in peak ozone on ozone exceedance days with current NOx concentrations. We recommend planting non- or low-isoprene emitting trees in cities with high NOx concentrations to avoid an increase in the frequency and severity of future ozone exceedance events.

Warming-Induced Vegetation Greening May Aggravate Soil Mercury Levels Worldwide.

Mercury, a neurotoxic substance, circulates globally, significantly stored in soils through atmospheric deposition and plant decay. Despite being deposited, mercury can be remobilized and released into the atmosphere and water, enhancing its global cycle. Recent research suggests that climate warming may amplify the remobilization of soil mercury, facilitating its incorporation into food webs that humans exploit. However, the potential geospatial feedback of soil mercury levels in response to warming remains unclear. By leveraging up-to-date soil measurements and observation-driven models, we determined the amount of mercury stored in global 0-100 cm soils to be 4.3 Tg (interquartile range: 2.5-6.3 Tg). Furthermore, our analysis indicates that warming likely aggravates global soil mercury levels, particularly in many temperate areas in East Asia, North Europe, and North America (>20 ng g-1 increase by 2100) due to warming-induced vegetation greening. Critically, observation-driven models raise the possibility that implementing ambitious mercury-emission-control schemes alone may be insufficient to counterbalance the positive feedback of soil mercury concentration, while process-based biogeochemical modeling demonstrates consistent patterns that reinforce this concern. These findings hold broad implications; for example, such feedback may catalyze mercury remobilization in land-ocean continuums and exacerbate human risks, stressing the necessity for continued reductions in greenhouse gas and mercury emissions.

Specifically targeting antimicrobial peptides for inhibition of Candidatus Liberibacter asiaticus.

AIMS: Huanglongbing (citrus greening) is a plant disease putatively caused by the unculturable Gram-negative bacterium Candidatus Liberibacter asiaticus (CLas), and it has caused severe damage to citrus plantations worldwide. There are no definitive treatments for this disease, and conventional disease control techniques have shown limited efficacy. This work presents an in silico evaluation of using specifically targeting anti-microbial peptides (STAMPs) consisting of a targeting segment and an antimicrobial segment to inhibit citrus greening by inhibiting the BamA protein of CLas, which is an outer membrane protein crucial for bacterial viability. METHODS AND RESULTS: Initially, a set of peptides with a high affinity toward BamA protein were screened and evaluated via molecular docking and molecular dynamics simulations and were verified in vitro via bio-layer interferometry (BLI). In silico studies and BLI experiments indicated that two peptides, HASP2 and HASP3, showed stable binding to BamA. Protein structures for STAMPs were created by fusing known anti-microbial peptides (AMPs) with the selected short peptides. The binding of STAMPs to BamA was assessed using molecular docking and binding energy calculations. The attachment of high-affinity short peptides significantly reduced the free energy of binding for AMPs, suggesting that it would make it easier for the STAMPs to bind to BamA. Efficacy testing in vitro using a closely related CLas surrogate bacterium showed that STAMPs had greater inhibitory activity than AMP alone. CONCLUSIONS: In silico and in vitro results indicate that the STAMPs can inhibit CLas surrogate Rhizobium grahamii more effectively compared to AMPs, suggesting that STAMPs can achieve better inhibition of CLas, potentially via enhancing the site specificity of AMPs.

Phloem and Xylem Responses Are Both Implicated in Huanglongbing Tolerance of Sugar Belle.

Although huanglongbing (HLB) is a devastating citrus disease, improved tolerant cultivars, such as Sugar Belle (SB) mandarin, have been identified. To understand the responses that HLB-affected SB undergoes, we compared 14CO2 fixation, carbohydrate export, phloem callose accumulation, relative expression of plant defense activators, and anatomical changes between healthy and infected SB trees versus susceptible Pineapple (PA) sweet orange. Eight- to ten-week-old leaves of infected SB showed a 2.5-fold increase in 14CO2 fixation and a 13% decrease in 14C-carbohydrate export, whereas HLB-affected PA presented a decrease of 33 and 50%, respectively. The mean distance of a callose deposit to its closest neighbor was 36% smaller in infected SB versus healthy, whereas in HLB-affected PA, it was 33% higher. Expression of papain-like cysteine proteases (PLCPs) was upregulated in SB but downregulated in PA. Infected SB showed minor alterations in the number of xylem vessels, a 16% larger xylem vessel lumen area, and a 14% increase in the proportional area of the xylem. In contrast, PA showed a 2.4-fold increase in the xylem vessel number and a 2% increase in the proportional xylem area. Three complementary mechanisms of tolerance in SB are hypothesized: (i) increased carbohydrate availability induced by greater CO2 fixation, mild effect in carbohydrate export, and local accumulation of callose in the phloem; (ii) activation of defense response via upregulation of PLCPs, and (iii) increased investment in the xylem structure. Thus, phloem and xylem modifications seem to be involved in SB tolerance.

Plant-Derived, Nodule-Specific Cysteine-Rich Peptides as a Novel Source of Biopesticides for Controlling Citrus Greening Disease.

Nodule-specific cysteine-rich (NCR) peptides, encoded in the genome of the Mediterranean legume Medicago truncatula (barrelclover), are known to regulate plant-microbe interactions. A subset of computationally derived 20-mer peptide fragments from 182 NCR peptides was synthesized to identify those with activity against the unculturable vascular pathogen associated with citrus greening disease, 'Candidatus Liberibacter asiaticus' (CLas). Grounded in a design of experiments framework, we evaluated the peptides in a screening pipeline involving three distinct assays: a bacterial culture assay with Liberibacter crescens, a CLas-infected excised citrus leaf assay, and an assay to evaluate effects on bacterial acquisition by the nymphal stage of hemipteran vector Diaphorina citri. A subset of the 20-mer NCR peptide fragments inhibits both CLas growth in citrus leaves and CLas acquisition by D. citri. Two peptides induced higher levels of D. citri mortality. These findings reveal 20-mer NCR peptides as a new class of plant-derived biopesticide molecules to control citrus greening disease.

Ancient plant DNA reveals High Arctic greening during the Last Interglacial.

Summer warming is driving a greening trend across the Arctic, with the potential for large-scale amplification of climate change due to vegetation-related feedbacks [Pearson et al., Nat. Clim. Chang. (3), 673-677 (2013)]. Because observational records are sparse and temporally limited, past episodes of Arctic warming can help elucidate the magnitude of vegetation response to temperature change. The Last Interglacial ([LIG], 129,000 to 116,000 y ago) was the most recent episode of Arctic warming on par with predicted 21st century temperature change [Otto-Bliesner et al., Philos. Trans. A Math. Phys. Eng. Sci. (371), 20130097 (2013) and Post et al., SciAdv (5), eaaw9883 (2019)]. However, high-latitude terrestrial records from this period are rare, so LIG vegetation distributions are incompletely known. Pollen-based vegetation reconstructions can be biased by long-distance pollen transport, further obscuring the paleoenvironmental record. Here, we present a LIG vegetation record based on ancient DNA in lake sediment and compare it with fossil pollen. Comprehensive plant community reconstructions through the last and current interglacial (the Holocene) on Baffin Island, Arctic Canada, reveal coherent climate-driven community shifts across both interglacials. Peak LIG warmth featured a ∼400-km northward range shift of dwarf birch, a key woody shrub that is again expanding northward. Greening of the High Arctic-documented here by multiple proxies-likely represented a strong positive feedback on high-latitude LIG warming. Authenticated ancient DNA from this lake sediment also extends the useful preservation window for the technique and highlights the utility of combining traditional and molecular approaches for gleaning paleoenvironmental insights to better anticipate a warmer future.

Green cities and vector-borne diseases: emerging concerns and opportunities.

Aligned with the Sustainable Development Goals, nature-based solutions such as urban greening e.g. public gardens, urban forests, parks and street trees, which aim to protect, sustainably manage or restore an ecosystem, have emerged as a promising tool for improving the health and well-being of an ever-increasing urban population. While urban greening efforts have undeniable benefits for human health and the biological communities inhabiting these green zones, disease vector populations may also be affected, possibly promoting greater pathogen transmission and the emergence of infectious diseases such as dengue, West Nile fever, malaria, leishmaniosis and tick-borne diseases. Evidence for the impact of urban green areas on vector-borne disease (VBD) transmission is scarce. Furthermore, because of vast disparities between cities, variation in green landscapes and differing scales of observation, findings are often contradictory; this calls for careful assessment of how urban greening affects VBD risk. Improved understanding of the effect of urban greening on VBDs would support planning, monitoring and management of green spaces in cities to sustainably mitigate VBD risks for surrounding urban populations.

Increasing tree cover and high-albedo surfaces reduces heat-related ER visits in Los Angeles, CA.

There is an urgent need for strategies to reduce the negative impacts of a warming climate on human health. Cooling urban neighborhoods by planting trees and vegetation and increasing albedo of roofs, pavements, and walls can mitigate urban heat. We used synoptic climatology to examine how different tree cover and albedo scenarios would affect heat-related morbidity in Los Angeles, CA, USA, as measured by emergency room (ER) visits. We classified daily meteorological data for historical summer heat events into discrete air mass types. We analyzed those classifications against historical ER visit data to determine both heat-related and excess morbidity. We used the Weather Research and Forecasting model to examine the impacts of varied tree cover and albedo scenarios on meteorological outcomes and used these results with standardized morbidity data algorithms to estimate potential reductions in ER visits. We tested three urban modification scenarios of low, medium, and high increases of tree cover and albedo and compared these against baseline conditions. We found that avoiding 25% to 50% of ER visits during heat events would be a common outcome if the urban environment had more tree cover and higher albedo, with the greatest benefits occurring under heat events that are moderate and those that are particularly hot and dry. We conducted these analyses at the county level and compared results to a heat-vulnerable, working-class Los Angeles community with a high concentration of people of color, and found that reductions in the rate of ER visits would be even greater at the community level compared to the county.

Associations between violent crime inside and outside, air temperature, urban heat island magnitude and urban green space.

There are more incidents of violence in summer and on hot days, a trend likely to be exacerbated by climate change. Urban areas experience additional temperature modulation due to the urban form, however, to date, no studies have considered the effect of the urban heat island (UHI) or green space with respect to the temperature-violence relationship. This study modelled the relationship between the number of daily violent crime incidents that occurred inside or outside between July 2013 and June 2018, and the average surface UHI or percentage greencover (including grasses, shrubs and trees) within each local government area in Greater Sydney, Australia. Panelised negative binomial time series regression models indicated that the violent crime rate was associated with higher surface UHI for crimes committed outside (p = 0.006) but not inside (p = 0.072). Greater percentage of all vegetation was associated with significantly lower rates of violent crime committed outside (p = 0.011) but was not associated with violent crimes committed inside (p = 0.430). More socio-economic disadvantage was associated with higher rates of violent crime committed inside (p = 0.002) but not outside (p = 0.145). Greater temperature was non-linearly associated with higher rates of violent crime committed both inside and outside (p < 0.001). The findings of this study are important because both violence and heat exposure are critical health issues and will be stressed by urbanisation and climate change. The expansion of green space and/or reduction in UHI may mitigate these effects.

Comparison of Insecticide Sprays in Alternate Rows and in All Rows on Asian Citrus Psyllid Control and Huanglongbing Progress in Sweet Orange Orchards.

One strategy to reduce huanglongbing (HLB) is controlling its insect vector, the Asian citrus psyllid (ACP) Diaphorina citri, by preventive insecticide sprays. The recommendation is to spray insecticide in all rows (conventional spray [CONV]), but some growers empirically spray in alternate rows (ALT) to increase the spray frequency without increasing the operating cost. Therefore, this work compared the effect of ALT with CONV on the ACP population and HLB incidence. The spray deposition (amount of metallic copper per leaf area), coverage (percentage of water-sensitive paper area covered by spray), and efficacy (ACP mortality) of each treatment were also evaluated on both sides of the trees. Two field trials were performed: Trial #1 compared ALT every 7 days (ALT7) with CONV every 14 days (CONV14), and trial #2 compared different spray frequencies of ALT with CONV every 7 days (CONV7). In trial #1, no differences were observed in the ACP population or HLB progress between ALT7 and CONV14 after 5 years. In trial #2, ALT7 presented the highest percentage of ACP and cumulative HLB incidence than CONV7 and ALT every 3 to 4 days, after 2 years. Hence, when the frequency of ALT was half the frequency of CONV, similar results were observed. Spray deposition, coverage, and efficacy were similar between tree sides in CONV, but they were uneven in ALT, resulting in higher values on the tree side that directly received the spray. Insecticide spray should be performed with the frequency enough to keep new shoots protected during their growth.

Variation in Pathogenicity and Subsequent Production of Sclerotia of Sclerotinia sclerotiorum Isolates in Different Cover Crops, Flower Strips, and Weeds.

Cover crops and flower strips are used in agricultural fields as part of integrated pest management strategies. However, their potential as secondary hosts of soilborne pathogens such as Sclerotinia sclerotiorum in oilseed rape cultivation is not fully comprehended. In the current study, we evaluated the effect of pathogen virulence on the development of Sclerotinia stem/leaf rot and sclerotia production in 33 plant species from 11 botanical families using two S. sclerotiorum isolates. Furthermore, the effect of sclerotial size on carpogenic germination was studied. Results showed that the pathogen's virulence significantly affected the occurrence and development of Sclerotinia stem/leaf rot and the subsequent production of sclerotia. Among all plant species tested, 26 were more susceptible to the highly aggressive S. sclerotiorum isolate, which produced more and bigger sclerotia in 17 species than the less aggressive isolate. Moreover, a stronger positive correlation was found between the relative lesion length of plants inoculated with the highly aggressive isolate and the number of sclerotia produced by this isolate (Spearman's rank correlation coefficient [rs] = 0.572; P = 0.004). Additionally, we found that larger and heavier sclerotia produced stipes and apothecia earlier and at a greater rate than smaller ones. The heavyweight class had the highest carpogenic germination rate (82.4%), followed by the average (67.2%) and lightweight classes (59.5%). Our findings highlight the need for further investigation into the potential risks associated with cover crops, weeds, and flower strips as secondary hosts of soilborne pathogens in agricultural fields.

Report of Citrus tristeza virus in Diaphorina citri (Hemiotera: Liviidae) insects of different sexes, color morphs, and developmental stages.

Diaphorina citri, also known as the Asian citrus psyllid, is the main vector of 'Candidatus Liberibacter asiaticus' (CLas) associated with citrus Huanglongbing. It has been reported that D. citri could also be infected by Citrus tristeza virus (CTV), a virus that has been previously reported to be vectored by certain aphid species. In this study, the CTV and CLas profiles in different organs, color variants, developmental stages, or sexes of D. citri insects were analyzed. Although no significant differences were found between nymphs and adults in CTV titers, we found that the third instar nymph of D. citri was more efficient in CTV and CLas acquisition compared to the fourth and fifth instars and adults. With the instars of D. citri development, the relationship between the acquiring of CTV and CLas by D. citri seemed to follow an inverse trend, with the titer of CLas increased and the titer of CTV decreased. No significant differences were observed between the 2 sexes of D. citri in acquiring either CTV or CLas titers in the field. However, no differences were drawn among the 3 color morph variants for CTV titers. CTV titers in the midguts of adult D. citri were significantly higher than those in the salivary glands. Both CTV-positive incidence and CTV titers in the midguts of adult D. citri increased with increasing exposure periods. This study provides new data to deepen our understanding of the CTV-involved interaction between D. citri and CLas.