ASHS 2025 Conference

Despite its challenges, non-chemical, reduced tillage vegetable production is of continued interest among researchers and growers as a way to improve soil health. Primarily success in this production method has been use of high biomass cover crops such as cereal rye terminated with a roller crimper. However alternative cover crops should be explored to diversify reduced tillage systems and to improve nitrogen synchrony. Sunn hemp (Crotelaria juncea) is a high biomass producing legume with potential to achieve weed suppression while reducing nitrogen immobilization in non-chemical, no-till vegetable production. A two-year study was conducted at the Meigs Horticulture Facility (Meigs) in Lafayette IN to assess the potential of sunn hemp as a cover crop suitable for rolling in a non-chemical, no-till vegetable production system. At Meigs roll success of three sunn hemp rolling dates was evaluated. Followed by Swiss chard production. Sunn hemp was rolled with and I and J roller crimper 60, 70, and 80 days after seeding. Prior to rolling sunn hemp height, above ground biomass (sunn hemp and weed), and roll success was measured 4 weeks after rolling by collecting terminated (senesced) and non- terminated (non- senesced) sunn hemp from 0.25m2 quadrats. Roll success was most related to sunnhemp height and biomass at time of rolling (R2 = 0.76 P < 0.01 ,0.68 P =0.15). In year one rolling was only successful 80 days after seeding, however in in year two rolling was successful at all seeding dates. More research is needed to understand mechanisms contributing to sunn hemp rolling success.

Tomatoes (Solanum lycopersicum L.) are the largest vegetable crop in the US by dollar value and represent a significant source of income for organic growers in the southeast. High tunnels allow growers to capture more profitable early markets, and the protection they offer provides additional benefits such as extended growing seasons and reduced leaf wetness/foliar disease. Most research on organic high tunnel tomatoes to date focuses on heirloom varieties due to their popularity among organic growers. However, advances in plant breeding in recent decades have yielded hybrids that combine the desirable culinary and aesthetic characteristics of heirlooms with the superior vigor and disease resistance of modern genetics. The objective of this study was to compare the performance and characteristics of such specialty hybrids under organic high tunnel, and organic and conventional field conditions in the Georgia Piedmont region. Two indeterminate cultivars were chosen for this project: ‘Estiva’, a mediterranean variety noted for setting fruit under high temperatures; and ‘Tomimaru Muchoo’, a Japanese pink slicer with thin skin and low acidity. Transplants of both varieties were grown under organic greenhouse conditions for several weeks before planting in organic field, organic high tunnel, or conventional field plasticulture systems. Data loggers were placed in each site to record temperature, relative humidity, PAR, and soil moisture. Fruits were harvested once per week and sorted by USDA marketability standards. Both total and marketable yield were recorded for each plot, as well as disease, pest, and physiological disorder damage. Subsampled fruits from each plot were measured for dimensions, mass, and qualitative aesthetic rating. Fruit and aboveground biomass samples from each plot were harvested, dried, and ground, then analyzed for elemental nutrient content. Soil samples were also taken from each plot prior to planting and after termination for nutrient analysis, pH, and organic matter. In 2023, the highest marketable yields were from the organic high tunnel, with ‘Estiva’ and ‘Tomimaru’ averaging 15491 and 15992 lb/A (FW), respectively; while the conventional field performed better in 2024, with average yields of 11807 (‘Estiva’) and 11611 lb/A (‘Tomimaru’). In 2024, ‘Estiva’ had substantial losses in the high tunnel due to blossom end rot, with 30% of the harvest being marketable as opposed to the 53% obtained from ‘Tomimaru’. These results suggest that under optimal conditions, organic growers can achieve similar yields of high-quality tomatoes to their conventional counterparts through proper application of high tunnels and superior varieties.

Organic lettuce production in hydroponic systems often yields less than conventional production. A previous study from the lab found that organic nutrient film technique (NFT) system with Pre-Empt organic fertilizer contained high concentrations of nitrite ions, which likely induce stress and resulted in lower lettuce yield. To address this toxicity, we conducted a series of studies investigating the effect of reservoir aeration, with the hypothesis that aeration would enhance microbial mineralization of organic nitrogen and reduce the concentrations of phytotoxic compounds such as nitrite and ammonium. In the first study, we aerated NFT reservoir tanks with 15.9 mL/L (2 oz/gal) Pre-Empt organic fertilizer. Aeration increased dissolved oxygen (from 6.4 to 7.8 mg/L) and decreased the ratio of nitrite-nitrogen to nitrate-nitrogen (from 1.1 to 0.2) but did not affect ammonium. As a result, aeration increased yield of ‘Casey’ lettuce by 2.6 times. In the second study, aeration did not increase lettuce growth when the concentration of Pre-Empt fertilizer decreased to 10.6 mL/L (1.4 oz/gal). Furthermore, in the third study, we found cultivar-specific response to the aeration of organic fertilizer. These results suggested that aeration can enhance mineralization of organic nitrogen, reduce root-zone nitrite toxicity and increase lettuce yield at high fertilizer rates and potentially depending on cultivar.

As environmental concerns grow, the horticultural sector is increasingly encouraged to adopt sustainable production practices. Certified Naturally Grown (CNG), established in 2002, offers a peer-reviewed certification rooted in organic principles and aims to foster a strong community network for small-scale producers. This research documents the process of certifying previously unmanaged farmland through the CNG program, offering research-based insights for growers considering certification. The project began with the revitalization of an overgrown, neglected field, focusing first on soil improvement and field preparation to support sustainable crop production. To build soil health and fertility, we planted both summer and fall/winter cover crop mixtures, which helped improve nutrient cycling and restore organic matter. In addition to soil improvement, we developed an integrated pest management (IPM) protocol tailored to our production system and selected OMRI-listed products to meet fertilization, pest, and disease control needs in compliance with CNG standards. To support certification, we also established a record-keeping system to document field activities, input usage, and compliance measures. Finally, we created postharvest handling protocols aligned with CNG principles to help ensure both food safety and product quality from field to market. Soil testing has shown an improvement in soil organic matter, plant-available soil nutrients, and an increase in soil microbial biomass. These gains reflect an improvement in overall soil health and provide a strong foundation for sustainable crop production. Ultimately, this project highlights the planning and steps required for successful CNG certification. The educational tools we create will serve as a guide for producers transitioning to CNG, equipping them with the knowledge to implement sustainable and resilient farming practices.

Momentum for sustainable and organic farming remains strong, driven by concerns for environmental stewardship, health, and social responsibility. As of the 2022 USDA Organic Certified Survey, the number of certified organic operations in the United States grew to 18,263, covering 5,083,623 acres. However, Mississippi continues to have a limited presence, with only 5 certified specialty crop operations as per the USDA Organic Integrity Database. Building on our initial findings, this year’s research continues to investigate the motivations and barriers producers face when adopting organic principles. In year two, we expanded the reach of our survey, pushing the 43-question instrument into all 50 states with the assistance of our partners. The survey remains focused on key challenges including social, environmental, and technical concerns. The core themes from year one—environmental consciousness, financial constraints, and the knowledge-implementation gap—remain prevalent, but we have also observed evolving trends in the responses. Producers continue to cite environmental and market motivations as key drivers. They emphasize the benefits of education on the producer and consumer level as a potential solution. Financial challenges remain a significant barrier, with many producers expressing concerns about the high costs of transition and the economic uncertainty during the process. New insights have emerged regarding the growing role of social networks and community support in facilitating the adoption of organic practices, suggesting that social capital may help mitigate some of the technical and financial challenges producers face. Our case study of a beginning farmer in Calhoun City, Mississippi, highlighted valuable insights into the specific challenges faced by farmers in a region where organic practices are still uncommon. It also highlighted the importance of bridging the knowledge gap and improving support systems for producers. The insights and data garnered have been used to develop a regional database of interested producers. These growers are helping refine recommendations and contribute to the development of targeted programs aimed at supporting the transition to organics including conferences, publication, and other educational efforts. These ongoing experiences continue to guide our understanding of the complexities of transitioning to organic agriculture, offering real-world examples that complement the survey data. As we move forward, we are also exploring how farmers' willingness to adopt organic practices evolves over time and how external factors may influence their decisions. This ongoing research plays a crucial role in advancing the transition to organic certification, ensuring producers are supported in their effort to pursue sustainable practices.

Studies in the Northeast United States and Canada have shown that sweetpotato yield can be comparable to the national average when grown with black plastic mulch. Western Washington has a diversity of microclimates, from the Pacific Coast to the Cascade Mountains, and assessing yield in response to growing degree days (GDD) will help growers determine if soil warming strategies are needed to achieve acceptable yield. This experiment was carried out in Mount Vernon, WA in 2024 and is being repeated in 2025. The experimental design was a split-split plot: the main plot treatment was bare soil and black polyethylene mulch (25.4 µm); the split plot treatment was cultivar, Covington and Cascade; and the split-split plot treatment was harvest date, every two weeks from 8 weeks after transplanting (WAT) to 18 WAT to assess root growth in response to accumulated GDDs. The experiment included 4 replications with 10 plants per plot, and raised beds with drip irrigation. Soil temperature was measured at 15-min intervals with sensors installed in both the mulch and bare soil plots. GDDs were calculated at two base temperatures, 10°C and 15.5°C, as both are reported in the literature. In 2024, for bare soil and plastic mulch treatments at base temperature 10°C, GDDs were 528 and 667 at 8 WAT (29 July), respectively, and 1080 and 1300 at 18 WAT (7 Oct.), respectively. At base temperature 15.5°C, GDDs for bare soil and plastic mulch treatments were 238 and 375 at 8 WAT and 428 and 635 at 18 WAT, respectively. At 8 and 18 WAT, GDDs for AgWeatherNet air temperature located 410 m from the field site were 629 and 1308 for 10°C base temperature and 138 and 275 for 15.5°C. Overall, black plastic mulch increased soil temperature by 1.78°C on average, and soil GDDs were 44% and 21% higher with plastic mulch compared to bare soil for a base temperature of 15.5°C and 10°C, respectively. At 18 WAT, root yield (US No. 1 and US No. 2) without accounting for wireworm damage was 11.7 t/ha for ‘Covington’ and 9.9 t/ha for ‘Cascade’ with plastic mulch and 7.7 t/ha for ‘Covington’ and 8.4 t/ha for ‘Cascade’ with bare soil. Sweetpotato yield in Mount Vernon, WA, was 35% greater on average with plastic mulch, but plastic mulch may not be necessary in warmer regions of the Pacific Northwest.

The profile of volatile organic compounds (VOCs) in tomato (Solanum lycopersicum) fruit significantly influences their sensory attributes, particularly aroma, which affects consumer preference. This study examines variation in VOCs between commercially processed tomato products and greenhouse-grown tomatoes, focusing on processing techniques and how they alter VOC profiles. Headspace solid-phase microextraction coupled with gas chromatography-mass spectrometry (HS-SPME-GC-MS) was employed for detailed VOC profiling. Optimization of HS-SPME parameters, including salt-assisted extraction, extraction temperature, and fiber selection, enabled precise identification and quantification of VOCs. The optimized conditions involved extracting samples in a 30% NaCl solution to maximize volatile release, adsorption onto a 50/30 µm DVB/CAR/PDMS fiber at 80 °C for 30 minutes, and analysis using a Restek Rtx-Wax column with helium as the carrier gas. SPME-GC-MS analysis confirmed that processing techniques significantly influence the release, chemical nature, and composition of VOCs. Commercially processed tomato products exhibited elevated levels of volatiles such as (Z)-3-hexenal and (E)-2-hexenal. Since processed products often undergo thermal treatments such as pasteurization and decontamination, the reduction in volatile composition compared to fresh, unprocessed tomatoes could be attributed to the thermal degradation of heat-sensitive compounds such as cis- and trans-hexanol, hexanal, geranial, and methyl salicylate, contributing to a pronounced cooked tomato aroma. In contrast, greenhouse-grown tomatoes, cultivated under controlled conditions, contained lower overall VOC concentrations but retained higher levels of methyl salicylate and norisoprenoids, yielding a milder, sweeter aroma profile, which is generally absent in processed products. This study underscores the impact of processing on tomato aroma and highlights the importance of optimizing analytical methods for VOC profiling. Detailed VOC profiling offers valuable insights for breeders and food processors seeking to enhance the flavor quality of both greenhouse-grown and processed tomato products. This research was supported by USDA-NIFA-2024-51181-43464 and USDA-NIFA-AFRI-2023-67013-39616 through the Vegetable and Fruit Improvement Center and the Institute for Advancing Health Through Agriculture at Texas A

Globe artichoke (Cynara cardunculus var. scolymus L.) is an herbaceous, perennial plant native to the Mediterranean region and belongs to the Asteraceae family. It requires adequate winter chilling for bud induction, yet susceptible to freeze damage. In subtropical or tropical climates, artificial flower induction or vernalization is necessary for winter crops. Our preliminary results indicate that gibberellic acid (GA3) effectively induces bud formation without chilling. Understanding crop phenology facilitates management planning and performance assessment under diverse conditions. This study used the Biologische Bundesanstalt, Bundessortenamt, CHemische Industrie (BBCH) scale to characterize the phenological development of artichoke cultivated in a subtropical climate with insufficient winter chilling. Seedlings of ‘Green Queen’ (GQ), ‘Imperial Star’ (IS), ‘Opal’ (OP), ‘20-063’, ‘22-017’, ‘23-057’, and ‘24-060’ cultivars were transplanted on 18 October 2024 in West Central Florida. Plants initially exhibited vegetative growth characterized by leaf development (Stage 1) and rosette formation (Stage 3–4) up to 79 DAP. GA3 applications at 62 and 76 days after planting (DAP) promoted vegetative growth by increasing both leaf number and size. Vegetative growth was most vigorous in ‘GQ’ and least in ‘20-057’, whereas in the Mediterranean climate, growth at this stage typically arrests through winter due to low temperatures. GA3 applications successfully induced bolting, initiating the transition to reproductive growth between 80 and 82 DAP. Buds reached the optimum maturity stage to harvest with the maximum diameter at around 115 DAP, earlier than the typical 120 to 150 days in annual culture. Marketable yields varied significantly among cultivars, from 2.69 t·ha–1 for ‘OP’ to 7.33 t·ha–1 for ’20-063’. By 160 DAP, mature buds exhibited floral opening with characteristic lilac-colored florets (Stage 6: flowering and capitulum formation). In Florida, although hot and humid summers constrain the harvest window, our results suggest that GA3-induced vernalization enables artichoke production during the winter months in a timeframe that is 5 to 35 days shorter than under Mediterranean conditions. This study advances understanding of artichoke adaptability to subtropical climates, promoting its potential as a winter specialty crop for edible and ornamental uses.

Arbuscular mycorrhizal fungi (AMF) are a widespread and naturally-present soil microorganism that form symbiotic relationships with the roots of terrestrial plants. These fungi have been credited with numerous host plant benefits, the most relevant to this study being their ability to improve plant-water relations through multiple mechanisms. Bell peppers are extremely vulnerable to drought stress and require high amounts of water, so the colonization of AMF could potentially help fortify peppers against this prevalent stressor. However, AMF populations are greatly affected by the disruptive agricultural practices utilized in vegetable production. Therefore, there is a need to research the integration of AMF into traditional production systems. Existing research on AMF is often inconclusive and inconsistent when compared across locations and environments due to their complex nature. An AMF trial was carried out at greenhouses in Raleigh, NC to examine the effect of AMF application on water use efficiency (WUE) in bell peppers. ‘Red Knight’ F1 hybrid bell pepper seeds were inoculated with a commercially available AMF spore product (Endomycorrhizae formulation). The seeds then germinated and grew for eight weeks to allow the AMF root colonization to establish. Afterwards, the pepper seedlings were transplanted into 2 gal pots and placed on weighing lysimeters before growing for four more weeks to allow the roots to establish in the pots. Two irrigation treatments were then applied to the plants: 100% container capacity (CC) and water deficit (WD). The 100% CC treatments were irrigated in daily intervals to keep the media at maximum soil moisture. The WD treatments were individually irrigated back up to 100% CC each time visual wilting symptoms presented for a plant. Water use for each plant was calculated throughout the growing season by weighing the pots and runoff-catchment containers at each irrigation event to precisely determine the amount of water available to each plant. At the end of the growing season, WUE was determined for each plant by comparing the total water used to the total biomass produced. Results show no difference in WUE for the control vs AMF inoculated plants under water deficit. However, there were some differences observed in other measurements collected, such as floral abortion rates, plant height, biomass, stomatal conductance, and water pressure potential.

Optimizing Harvest Timing for Enhanced Hop Quality in a Subtropical Climate Alvaro J. Bautista* and Shinsuke Agehara University of Florida, Institute of Food and Agricultural Sciences, Gulf Coast Research and Education Center, 14625 County Road 672, Wimauma, FL 33598, United States *Presenter: Alvaro J. Bautista Corresponding author: Shinsuke Agehara (sagehara@ufl.edu) Hops (Humulus lupulus L.) are a key ingredient in brewing, contributing bitterness, aroma, and microbiological stability. While traditionally cultivated in temperate climates, our previous research has demonstrated that subtropical regions like Florida offer unique opportunities for hop production, enabling two production cycles per year with supplemental lighting. Harvest timing is critical for optimizing hop cone biochemical composition, particularly alpha acids (AA), beta acids (BA), and essential oils, which directly influence beer quality. This study examined the seasonal and developmental dynamics of ‘Cascade’ hop cone chemistry to determine the optimal harvest window for both spring and fall growing seasons. Data were collected from 2021 to 2024 from the plants established in 2021 at the University of Florida’s Gulf Coast Research and Education Center in west-central Florida. Cone samples were collected at different days after flower induction (DAFI) to assess changes in AA and BA, cohumulone and colupulone, and essential oil composition. Acid levels showed significant seasonal variation. In spring, AA and BA ranged from 9.38% and 5.48% in 2021 to 4.48% and 2.0% in 2024, respectively. In fall, AA and BA ranged from 4.7% and 2.49% in 2021 to 2.97% and 2.0% in 2024, respectively. Acid accumulation also showed seasonal patterns, peaking at 36–48 DAFI in spring compared to 24–30 DAFI in fall. In contrast, cohumulone and colupulone maintained stable levels around 27.54% of total AA and 47.79% of total BA, respectively, throughout the study. Essential oil content increased during cone maturation, reaching its optimal aromatic profile at 36–42 DAFI (1.5 ml/100g). Myrcene (81.8% of total oil), the dominant terpene across all seasons, followed the same trend as total essential oil content. Humulene and caryophyllene peaked between 24 and 36 DAFI (19.7% and 10.9.% of total oil, respectively), while geraniol and linalool remained stable (0.5% and 0.7% of total oil, respectively) throughout maturation. These findings provide a foundation for optimizing hop production in non-traditional climates and highlight the importance of precise harvest timing to enhance hop quality for brewing applications. Future research will explore additional environmental, physiological, and management factors influencing hop maturation under subtropical conditions.

A comprehensive, two-year field evaluation of bicolor, white, and yellow sweet corn (Zea mays var. saccharata) varieties was conducted in southern Georgia during the spring seasons of 2022 and 2024. This research aimed to evaluate the yield and quality performance of commercial supersweet sweet corn varieties for the main kernel color market segments. The experiment was conducted at the Hort Hill Research Farm on the University of Georgia Tifton Campus. A total of ten bicolor, five white, and five yellow sweet corn varieties were used in this study. Significant interactions were observed between years and varieties, impacting ear characteristics and marketability. Overall, 2022 exhibited significantly higher ear and shank lengths, while 2024 had increased blank tip lengths and higher unmarketable ear counts. Among the bicolor varieties, ‘Redemption’ demonstrated exceptional performance with the highest ear length and width measurements, shank length, and the lowest blank tip measurements. ‘Grizzly’ had the lowest ear width, shank length, and highest blank tip measurements, while ‘American Dream’ recorded the shortest ear length. ‘Obsession’ and ‘Seminole Sweet’ had the highest marketable yield and 48-ear boxes per acre, reflecting their superior yield performance, whereas ‘Grizzly’ exhibited the lowest performance parameters, including the lowest marketable yield, total ear counts, and 48-ear boxes per acre. Additionally, ‘Superb’, ‘American Dream’, and ‘Courage’ recorded higher unmarketable ear counts per plot, which ultimately resulted in a significantly lower percentage of marketable ears. For the white varieties, there were no significant differences in ear characteristics and yield parameters. However, the yellow varieties displayed statistically significant differences in ear width and shank length. ‘GSS1170’ excelled, with the highest ear width and shank length, making it an excellent option for yellow corn production. Varieties ‘SC1336,’ ‘Astronaut,’ and ‘Passion’ had significantly higher unmarketable ear counts, with total ear counts also varying significantly among varieties, indicating differences in both productivity and marketability. Based on these research findings, the recommended varieties for optimal performance in ear characteristics and marketability are ‘Obsession’, ‘Seminole Sweet’, and ‘Redemption’ for bicolor corn and ‘GSS1170’ for yellow corn. These varieties exhibited excellent yield performance, making them ideal choices for growers seeking to increase yield. Conversely, since white corn varieties did not exhibit significant differences for any ear characteristics or marketability parameters, no specific recommendations can be made for this category.

Agrivoltaics is a production system that allows for dual land use through the deployment of solar panels for energy production while maintaining agricultural production underneath and/or between solar panels. This study was conducted at the Alliant Solar farm at Iowa State University, Ames, IA. Treatments included bell pepper (Capsicum annuum ‘SVPB8415’) grown between and outside (open-field) the solar panels. For the solar panel treatment, two raised beds with white plastic mulch were created on each side of the single-axis solar tracking panels. Each bed was 19.5m long. Two beds on each side were spaced 1.5m (center to center). Two rows of open-field peppers served as the control treatment. Control beds were 6.7m long. All treatments were replicated three times. Peppers were transplanted on June 6, 2024 at 0.3m spacing, double row. HOBO soil temperature, air temperature, and light intensity sensors were installed on the same day. No pesticides were needed to manage pests. A total of 6 harvests occurred throughout the season on a weekly basis between September 6 and October 14. Plants between the solar panels yielded 52.1 kg per row while the open-field yielded 27.0 kg, a 48% increase in the solar treatment. From June to September, the air temperature was cooler than the control on average by 4 degrees Fahrenheit while the soil temperature was 3 degrees Fahrenheit cooler. Based on first year results, bell peppers show promise within an agrivoltaics production system. More data will be collected in the coming years on plant growth characteristics, soil moisture, and postharvest quality of peppers.

Climate change presents a serious challenge for the future of agricultural production, with communities around the world undergoing agroecological disaster as a result of rapidly developing climatic conditions. Among the most pressing concerns for coastal production is sea level rise and salt intrusion into agricultural soils. Such is the case with Florida, which is regarded as a developing “ground zero” of the climate crisis. Along with California, Florida is the largest tomato producer in the country but is greatly at risk from sea level rise and saltwater intrusion, and tomato crop suffers considerably under salt stress. However, regenerative agriculture (RA) techniques present an opportunity for reducing the effects of saltwater intrusion, as they can enhance crop resistance to stresses and facilitate Na leaching out of soil biomes and improve crop yields. This research project aims to test two RA techniques (green manure and mycorrhizal inoculation) as ameliorating agents of salt stress in tomato (Solanum lycopersicum cv. “Sanibel”). In greenhouse controlled conditions, two treatments of pigeon pea green manure was applied to soil prior to the planting of tomatoes (0g mulch [control] and 60g) and tomatoes were subject to two mycorrhizae inoculation conditions (no inoculation [control] and inoculation with the salt-resistant species Glomus intraradices). Tomato plants were then subjected to four irrigation water salinities (0, 4, 8, and 12 dS m-1). Saline treatments were prepared using Instant Ocean® Sea Salt and distilled water. Tomato plant chlorophyll content and fruit texture quality parameters were analyzed in order to determine the salt-stress ameliorating efficacy of these regenerative techniques.

Brassinosteroids (Brs) are a natural group of hormones known for their significant impact on responses to both biotic and abiotic stresses across various plant species. Brs can also influence plant growth and fruit maturation. With the recent availability of commercial formulations, this plant growth regulator is becoming an increasingly popular management tool in agriculture. Our team has been working on understanding BRs mode of action in citrus, because information is still scarce. In Florida, citrus industry is now in decline due mainly to the citrus greening disease (HLB), which has become endemic in the state, with no potential cure in the horizon. The disease reduces internal fruit quality and compromises viability of young, newly planted citrus trees. Our work has unveiled that Homobrassinolide (HBr) may increase internal maturation in sweet orange under citrus greening endemic conditions. We have determined the optimal application rate and the most effective timing for Hamlin and Valencia cultivars. We have shown that the beneficial effects of HBr are more pronounced in the healthier trees. This has led us to adapt the use of HBr in combination with oxytetracycline (OTC) injections, as growers in Florida are now injecting OTC in mature trees to reduce HLB. Our results show that HBr, when used on OTC-injected trees, improve internal fruit quality significantly. In addition, we have found that treating young, newly planted trees with HBr induces a strong immune response by activating the salicylic acid pathway, resulting in a delay in HLB infection. We have also shown that other Br analog, Epibrassinolide (EBL) improve the cold tolerance of citrus trees when young, treated plants were exposed to -4 ℃ for 24 hours. In addition, we have also observed EBL are helpful in improving the postharvest fruit quality. This is of special interest in the northern part of the state, where fresh market citrus industry is expanding, as region often experiences frequent chilling conditions during winter months. All in all, we are showing that Brs may be a ready-to-use tool in Florida citrus industry.

Huanglongbing (HLB), a devastating bacterial disease presumed to be caused by Candidatus Liberibacter asiaticus, disrupts normal plant physiology by inducing hormonal imbalances that impair growth, fruit development, and defense responses. With no known citrus germplasm exhibiting resistance to HLB, effective management strategies are essential for sustaining citrus production. This study focuses on the combined application of methyl salicylate (MeSA), a systemic acquired resistance (SAR) inducer, and gibberellic acid (GA₃), a growth-promoting hormone, as a potential strategy to improve tree health and mitigating symptoms in HLB-affected citrus orchards. The study is being conducted at UF-CREC in Lake Alfred, Florida, on 15-year-old Valencia trees grafted onto Swingle rootstock. Four treatments are being evaluated: Control, GA₃, MeSA, and GA₃ MeSA. Trees were sprayed every 45 days from July to November 2024 with GA₃ and MeSA at 10 ounces per acre. The study assesses key production parameters, including yield, fruit drop, canopy density, and fruit quality. Preliminary results indicate that GA₃ application reduced preharvest fruit drop by 57% compared to the control. The leaf water content was significantly higher in Ga MeSa (58.42%) as compared to Control. No significant differences in canopy density were observed across treatments. Leaves were collected for molecular analysis on Days 7, 14, 30, 46, and 60 after the first treatment application. Differential gene expression analysis revealed significantly lower transcript levels of Rboh and LOX2 within 7 to 14 days post-treatment in GA MeSA, suggesting a potential reduction in oxidative stress. In contrast, CDR1 expression was significantly higher in MeSA treated leaves between days 30 and 45, likely indicating SAR activation. These physiological responses may contribute to improved tree performance under HLB pressure. The study will continue into the next year to refine application strategies and better understand the sustained impact of these treatments on tree health and productivity.

Pre-harvest fruit drop significantly challenges citrus orchard yield and economic viability, especially those affected by Huanglongbing (HLB). This issue is relevant in Florida’s citrus industry. This study investigated the efficacy of propionic acid he experiments applied three monthly doses of propionic acid in two consecutive years—in 2023 treated doses were 300 ppm, 1,100 ppm and 2,200 ppm— to trees, with an untreated group serving as the control. For this experiment, results indicated that the 1,100 ppm of propionic acid was most effective in controlling fruit drop, significantly reducing losses by 30% compared to the control. In 2024, the second experiment aimed to fine-tune doses. Trees were treated with three monthly doses of propionic acid utilizing 700 ppm, 1,100 ppm, and 1,400 ppm, with an untreated group serving as the control. Results showed that the 700 ppm dose was the most effective treatment in preventing fruit drop, retaining 15% more fruit than untreated trees. In both years, propionic acid increased average fruit weight. The 700 ppm dose improved yield by 36% compared to the control in 2024, while the 1,100 ppm dose led to a 17% increase in 2023 and 6% in 2024. Propionic acid did not alter fruit quality parameters, including °Brix and acidity. These findings suggest that propionic acid is a promising management tool for reducing pre-harvest fruit drop under HLB conditions.

Huanglongbing (HLB), also known as citrus greening, is a devastating disease of citrus and has severely impacted the citrus industry in Florida, causing substantial economic losses. With no known cure, management practices just aim to mitigate the harmful effects on the tree. Recent studies have shown that the 5 monthly foliar applications (September-January) of gibberellic acid (GA) can reduce preharvest fruit drop, improve fruit set, and enhance tree health. The potential impact of these findings is huge for commercial citrus production; however, growers are looking for alternatives to foliar application as foliar sprays are highly weather dependent and expensive, currently an air blast sprayer application can range anywhere from $30 to $50 per acre. Therefore, it becomes critical to find alternatives to foliar GA application. Supply of GA to the plants through irrigation could be a valid alterative instead of foliar application. This study explores the feasibility of GA application through irrigation as an alternative to foliar sprays. Specifically, we investigated GA uptake efficiency through citrus roots, its effects on overall plant growth, and transcriptomic changes in leaves and roots. Preliminary results indicate that both foliar (GF) and root applications (GR) induced tree responses, altering the hormone profiles in leaves and roots. Fifteen days post application, GR showed significantly higher concentration of GA₁ (950 ng/g fresh weight (FW)), GA₃ (450 ng/g FW), and GA8(112 ng/g FW) in the roots whereas these hormones were undetectable in the GF or untreated controlled. In the leaves, GA3 was significantly higher (210 ng/g FW) in GF but undetectable in untreated and GR. At 30 days post treatment, an enhanced leaf growth response was observed in GF trees with a mean new growth of 35 leaves as compared to 20.2 in GR and 17.8 in untreated control. Similarly, a 60-day hydroponic study demonstrated that root GA application significantly increased leaf production (p = 0.04). Bud growth was also significantly higher in root-treated plants compared to controls at both 10 days (p = 0.01) and 20 days (p = 0.01) post-application These preliminary findings suggest that root-applied GA does not mimic foliar application effects but offers some benefits for plant growth. An in-depth, long-term analysis is underway to validate the potential of GA delivery via irrigation.

Brassinosteroids (BRs) are essential plant steroid hormones that regulate a wide range of developmental and physiological processes. In addition, these hormones play a significant role in helping plants cope with stress by modulating responses to various stressors, including heat, cold, drought, and heavy metals. Freezing temperatures during winter and spring pose a serious threat to citrus production, putting the sustainability of this newly emerging citrus industry in north Florida. Based on the protective effects of BRs, we hypothesized that exogenous application of BRs could enhance the basal tolerance of citrus plants exposed to freezing temperatures. To test this hypothesis, we evaluated the photosynthetic performance and cellular damage of cold sensitive grapefruit (cv. Ray Ruby) plants sprayed with BRs (6 ppm) under freezing stress. Plants were treated with BRs (0 and 6 ppm) at 12, 24, and 48 hours before freezing stress (hbfs). Plants maintained at 20°C and sprayed with BRs (0 and 6 ppm) served as controls. Following treatment, the plants were placed in a freezing chamber and subjected to a gradual temperature decrease until reaching -6°C, where they were maintained for 1.5 hours. Freezing stress induced greater cellular damage in exposed plants compared to those kept at 20°C. However, BRs-treated plants at 12, 24, and 48 hbfs showed approximately 30% less cellular damage compared to water-sprayed plants. Photosynthetic parameters were affected by freezing stress, leading to reductions in CO₂ assimilation (

The Georgia citrus industry is rapidly growing. The citrus farmgate value increased by ~70% from 2022 ($22.4M) to 2021 ($13.2M). More acres of citrus are put in every year and, as of 2024, there are nearly 5,000 acres of citrus across the southern half of the state. Of this acreage approximately 60% are satsumas. This has generated a bottleneck for packinghouses as a majority of the citrus grown in the state reach an acceptable maturity at the same time. Georgia citrus growers have expressed an interest in expanding the harvest window of their existing plantings so more fruit can reach the market. The plant growth regulator, gibberellic acid (GA), has historically been used to delay color break in Florida citrus. Unfortunately, the existing recommendations from Florida are not applicable to the citrus varieties grown in Georgia. The present works aims to develop GA recommendations for Georgia satsumas. GA was applied at a rate of 0, 8, 10, 15, 20 ppm (n = 4) prior to color break in August 2024. The 15 and 20 ppm concentrations saw significantly less red and yellow color development by mid-December (p

The citrus industry experiences considerable losses due to a physiological rind disorder that compromises mandarin fruit quality and marketability—particularly in cultivars like Satsuma Owari. This disorder, characterized by water-soaked areas that progress to brown lesions, is likely triggered by multiple factors, including environmental conditions such as high relative humidity and rainfall. It typically appears after fall rain events and is more prevalent in fruit from the outer canopy. Our study, conducted in a commercial orchard in California’s San Joaquin Valley, explored the role of environmental conditions, rind water status, and potential management strategies. We found that treatments applied at the color break stage, 2,4-dichlorophenoxyacetic acid (2,4-D, 16 mg/L), gibberellic acid (GA₃, 20 mg/L), and Vapor Gard® (0.5% v/v)—significantly reduced rind damage. However, GA₃ delayed external color development by approximately four weeks. Susceptibility to rind disorder varied by cultivar, with Kishu being the most susceptible, followed by Satsuma Owari and Gold Nugget, while Page, Tango, and W. Murcott exhibited greater tolerance. We also investigated biochemical, hormonal, and molecular changes associated with the disorder. Damaged tissues showed reduced cellulose concentrations but similar levels of pectin and hemicellulose compared to healthy tissue. Additionally, damaged rinds had higher hydrogen peroxide (H₂O₂) content and increased peroxidase (POD) and polyphenol oxidase (PPO) activities. Metabolomic and hormonal profiling identified 76 metabolites, with 43 differing significantly between healthy and damaged tissues, highlighting the involvement of jasmonic acid and related compounds in the disorder’s development. Transcriptomic analysis further revealed differential expression of genes involved in stress responses, cell wall degradation, and hormone signaling between healthy and affected tissues. These findings suggest that delaying rind senescence using targeted treatments may reduce the incidence of this disorder. This research provides new insights into the physiological, biochemical, and molecular basis of mandarin rind disorder and offers practical management strategies to mitigate fruit losses across different varieties.