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Agronomy
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Current Status and Future Prospects of Citrus Disease Management and...
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Current Status and Future Prospects of Citrus Disease Management and Resilience

A special issue of Agronomy (ISSN 2073-4395). This special issue belongs to the section "Pest and Disease Management".

Deadline for manuscript submissions: 31 October 2026 | Viewed by 1922

Editors

Dr. Fernando Alferez

E-Mail Website
Guest Editor
Horticultural Sciences Department, Southwest Florida Research and Education Center, Institute of Food and Agricultural Sciences (UF/IFAS), University of Florida, Immokalee, FL 34142-9515, USA
Interests: horticulture; citrus physiology; hormonal regulation of citrus fruit abscission; citrus tree health; fruit maturation and quality; postharvest technology; fruit senescence
Special Issues, Collections and Topics in MDPI journals
Dr. Ute Albrecht

E-Mail Website
Guest Editor
Horticultural Sciences Department, Southwest Florida Research and Education Center, Institute of Food and Agricultural Sciences (UF/IFAS), University of Florida, Immokalee, FL 34142-9515, USA
Interests: citrus; citrus production; citrus diseases; rootstocks; rootstock propagation; root traits; rootstock–scion interactions; huanglongbing
Special Issues, Collections and Topics in MDPI journals
Dr. Caroline Tardivo

E-Mail Website
Guest Editor Assistant
Horticultural Sciences Department, Southwest Florida Research and Education Center, Institute of Food and Agricultural Sciences (UF/IFAS), University of Florida, Immokalee, FL 34142-9515, USA
Interests: citrus physiology; rootstocks; HLB management

Special Issue Information

Dear Colleagues,

Citriculture faces unprecedented global challenges due to the increasing prevalence of devastating diseases, most notably Huanglongbing (HLB). Beyond HLB, citrus production is constrained by a wide range of fungal, bacterial, and viral pathogens that collectively reduce tree health, productivity, and grove longevity. These biotic stresses are often exacerbated by abiotic constraints, leading to disruptions in tree physiology and performance. Ensuring the sustainability of citrus production, therefore, requires an integrated understanding of disease impacts and the development of strategies that enhance host resilience. This Special Issue aims to provide a platform for innovative research addressing citrus disease management across diverse production systems. We invite original research articles and reviews that explore physiological, pathological, and horticultural responses to disease, with an emphasis on scion–rootstock interactions, mechanisms of tolerance, nutritional and cultural modulation, and therapeutic delivery systems. Contributions that bridge fundamental plant biology and applied horticulture are particularly encouraged, including studies that evaluate the effects of disease and management on vegetative growth, root systems, yield, and fruit quality. By synthesizing current advances, this collection aims to inform science-based practices and promote resilient citrus production in the face of increasing biotic and abiotic pressures.

Dr. Fernando Alferez
Dr. Ute Albrecht
Guest Editors

Dr. Caroline Tardivo
Guest Editor Assistant

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All submissions that pass pre-check are peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 250 words) can be sent to the Editorial Office for assessment.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-anonymized peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Agronomy is an international peer-reviewed open access semimonthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 2600 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

  • citrus diseases
  • huanglongbing (HLB)
  • disease management
  • tree resilience
  • citrus physiology
  • rootstock tolerance
  • biotic–abiotic stress interactions
  • grove management

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Published Papers (2 papers)

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Research

20 pages, 12303 KB  
Article
Get It Vigorous! Supplemental Tree Growth Regulators and Mineral Nutrients Can Improve Sweet Orange HLB Tolerance
by Camilo Lázaro Medina, Paulo Roberto de Camargo e Castro, Ricardo Silverio Machado, Nárcya Trindade de Souza and João Paulo Rodrigues Marques
Agronomy 2026, 16(14), 1390; https://doi.org/10.3390/agronomy16141390 - 22 Jul 2026
Viewed by 520
Abstract
Huanglongbing (HLB) is the main disease affecting citrus crops, and in the absence of resistant commercial cultivars, alternative management strategies are required. This study aimed to evaluate the effect of early application of tree regulators associated with foliar nutrition on tree development, fruit [...] Read more.
Huanglongbing (HLB) is the main disease affecting citrus crops, and in the absence of resistant commercial cultivars, alternative management strategies are required. This study aimed to evaluate the effect of early application of tree regulators associated with foliar nutrition on tree development, fruit quality, tolerance to HLB in sweet orange trees and vascular tissue organizations. The experiment was conducted in a commercial Citrus sinensis “Lima Verde” orchard, with asymptomatic (PCR−) and symptomatic (PCR+) tree, distributed in a completely randomized design with eight replications per treatment. The following six treatments were evaluated: negative control (asymptomatic trees, PCR−); positive control (symptomatic trees, PCR+); foliar application of gibberellic acid; foliar application of 2,4-D; foliar spraying of nutrients solution; and a combination of nutrients solution with gibberellic acid and 2,4-D. The evaluations included disease severity, canopy growth, analysis of mineral nutrients by fruit, dry mass, fruit quality, and histopathological analysis of the phloem and xylem. The integrated treatment (foliar nutrition + growth regulators) significantly reduced HLB symptom severity, promoted canopy growth comparable to healthy trees, and decreased fruit drop by 62.7% relative to the untreated HLB control. Fruit yield increased from 9.89 to 22.50 kg tree−1, representing a 127% increase, while harvested fruit number increased from 71.0 to 139.8 fruits tree−1. The combined treatment also restored fruit diameter to values similar to healthy trees, increased total fruit dry matter from 14.5 to 24.2 g, and maintained soluble solids (9.56 °Brix) close to the healthy control (10.33 °Brix). Fruit zinc concentration increased by 48% compared with untreated HLB-infected trees. Histological analyses demonstrated enhanced cambial activity, larger phloem and xylem areas, reduced starch accumulation, and improved vascular integrity in treated trees. These findings highlight the potential of integrated tree regulators and nutritional approaches as a valuable alternative for improving tree performance and tolerance under HLB prevalent conditions. Full article
(This article belongs to the Special Issue Current Status and Future Prospects of Citrus Disease Management and Resilience)
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18 pages, 2402 KB  
Article
Combining Individual Protective Covers and Homobrassinolide Treatment Prolongs Tree Health and Increases Fruit Yield in Young Tango Mandarin Trees Under Endemic HLB
by Saoussen Ben-Abdallah and Fernando Alferez
Agronomy 2026, 16(14), 1321; https://doi.org/10.3390/agronomy16141321 - 10 Jul 2026
Viewed by 641
Abstract
Huanglongbing (HLB), caused by Candidatus Liberibacter asiaticus (CLas) and vectored by Asian citrus psyllid (Diaphorina citri), remains a major constraint to sustainable citrus production. In Florida, individual protective covers (IPCs) have been adopted as an effective psyllid exclusion tool [...] Read more.
Huanglongbing (HLB), caused by Candidatus Liberibacter asiaticus (CLas) and vectored by Asian citrus psyllid (Diaphorina citri), remains a major constraint to sustainable citrus production. In Florida, individual protective covers (IPCs) have been adopted as an effective psyllid exclusion tool by shielding young trees from this vector of the phloem-dwelling bacterium CLas. Brassinosteroids (BRs), a class of plant steroid hormones, are being explored as a treatment to mitigate HLB and are approved for commercial use in the state. We investigated the effect of IPCs combined with homobrassinolide (HBr) applied as a foliar spray on CLas titer, canopy volume, tree growth, yield, fruit quality, and defense-related gene expression of the salicylic acid (SA) pathways in ‘Tango’ mandarin grafted on sour orange (SO) or US-942 rootstocks. After being covered with IPCs in the field for three years, trees were subjected to monthly foliar application of HBr upon IPC removal. The experiment included four treatment groups: trees with IPC and HBr spray (IPC HBr+), IPC without HBr (IPC HBr-), no-IPC with HBr (no-IPC HBr+), and no-IPC without HBr (no-IPC HBr-). IPCs effectively delayed bacterial infection for six to nine months after IPC removal, maintaining higher cycle threshold (Ct) values (lower CLas titers) than in no-IPC trees, confirming the protective effect of IPCs against early CLas colonization. The combination of IPCs and HBr spray significantly enhanced canopy volume, particularly in trees grafted on SO. This effect was sustained over one year and was consistently greater in IPC HBr+ trees than in IPC HBr- and no-IPC HBr+ or HBr- trees, suggesting a synergistic effect of the combined therapy on enhancing tree growth. The tree height and trunk diameter were primarily improved by IPC, regardless of HBr treatment. IPC-treated trees exhibited significantly greater height and trunk diameters (scion and rootstock) than no-IPC trees across one or both rootstocks, indicating that IPCs alone contribute to these horticultural growth improvements. IPC trees also showed reduced preharvest fruit drop compared to the no-IPCs trees, resulting in higher yields, with additional gains observed in IPC HBr+ trees on SO. Fruit quality attributes, including °Brix, titratable acidity, peel color, and size, did not differ significantly among treatments. Importantly, gene expression analysis revealed early and sustained upregulation of key SA pathway genes in IPC HBr+ trees, indicating that HBr effectively activated systemic acquired resistance (SAR), particularly on SO rootstock. This study highlights the complementary roles of IPCs and HBr in the management of HLB. While IPCs provided essential early protection against CLas and promoted long-term horticultural growth, HBr enhanced early canopy development, activated host defense mechanisms, and enhanced yield. The integration of both approaches offers a sustainable and effective strategy to protect young citrus trees, delay CLas infection, and improve tree health and productivity under endemic HLB. Full article
(This article belongs to the Special Issue Current Status and Future Prospects of Citrus Disease Management and Resilience)
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