Dahlia Doctor Research Library: Dahlia Tuber Rot, Tuber Collapse, and Clean Stock

A Curated Knowledge Card Collection

Copyright © 2026 by Steve K. Lloyd
All Rights Reserved

Dahlia tuber losses in storage and propagation are not random. They follow recognizable patterns: wet collapse during forcing, stem rot under humid field conditions, and silent bacterial infections that travel through propagation chains without symptoms until the damage is done. Understanding those patterns requires knowing which pathogens are involved, how they enter and spread, what conditions favor their activity, and where the current limits of diagnosis and prevention actually lie.

This collection assembles the research evidence on dahlia tuber rot in its full range: fungal pathogens causing field and storage losses, the bacterial soft rot complex responsible for the phenomenon Dutch growers call ploffers, the diagnostic testing developed to detect Erwinia before collapse occurs, and the clean-stock systems designed to interrupt the cycle at the propagation stage. The evidence base here is unusually specific to dahlia, reflecting decades of Dutch and international research on a problem that has cost commercial producers significant losses.

The collection does not cover storage substrate, dormancy, or overwinter survival conditions. Those topics are treated in the companion collection on dahlia tuber storage, dormancy, and overwinter survival. Skin set, curing, and wound healing at lifting are treated in the companion collection on lifting timing, skin set, curing, and storage readiness.

Each post in this series presents a curated set of Dahlia Doctor Knowledge Cards organized around a specific research topic. A Knowledge Card summarizes one scientific or technical source using a consistent structure: study system, experimental context, experimental design, key results, mechanistic insight, practical guidance, and why the source matters to dahlia growers and researchers.

These summaries represent original interpretive work. They are intended as a research guide, not a substitute for reading the original papers. Each citation title links to a Google Scholar search for that source, opening in a new tab, to help you locate the original publication independently.

Each Knowledge Card appears once in this collection, placed in the topic cluster where it contributes most directly. Some sources are relevant to more than one cluster. Placement reflects primary emphasis rather than exclusive relevance.

This collection focuses on tuber rot symptoms and pathogen identity, the bacterial soft rot and poppers complex, diagnostic testing and its limits, and clean-stock prevention systems. It does not cover storage substrate, dormancy, or overwintering conditions. Those are treated in the companion collection on dahlia tuber storage, dormancy, and overwinter survival. Skin set, curing, and wound healing at lifting are treated in the companion collection on lifting timing, skin set, curing, and storage readiness.

KC-0418, Van Leeuwen and Trompert (2005), appears in this collection for its full Erwinia chrysanthemi and poppers disease narrative. The same source appears in the companion collection on lifting timing and storage readiness, where its tuber maturity and potting-up moisture findings have a distinct application. In this collection, the disease findings are the primary focus.

KC-0420, van Doorn et al. (2008), covers multiple bulb crops including dahlia. It is dahlia-including evidence, not dahlia-exclusive, and is used here for the broader Erwinia and Dickeya soft-rot complex in ornamental bulb crops.

KC-0479, Bruton (1994), covers fruits and vegetables, not dahlia. It is included as general postharvest pathology support for the principles of wound entry and latent infection that the dahlia-direct clean-stock sources document in practice.

Publication Type
Doctoral Dissertation

Full Citation
Ali, E. O. H. (2004). Pathological studies on dahlia tuber rots (Doctoral dissertation). Department of Agricultural Botany, Faculty of Agriculture at Moshtohor, Zagazig University.

Study System
Dahlia pinnata; fungal and bacterial pathogens associated with tuber rot under Egyptian field and storage conditions.

Experimental Context
Field and storage tuber rot diseases investigated through isolation, identification, pathogenicity testing, and chemical control trials.

Experimental Design
Isolation of pathogens from rotting tubers; pathogenicity testing through inoculation; physiological and biochemical assays characterizing enzyme activity and host response; chemical control trials evaluating management options.

Key Results
Sclerotium rolfsii was identified as the most destructive tuber rot pathogen under the tested conditions. Disease severity was linked to wounding, inoculum density, and pathogen enzyme activity. Multiple fungal and bacterial pathogens were associated with tuber rot, with virulence varying by species and conditions.

Mechanistic Insight
Pathogen virulence was driven by production of pectolytic and cellulolytic enzymes that degrade tuber cell walls, combined with biochemical shifts in host tissue that reduce resistance. Wound sites provided entry points that amplified disease severity.

Practical Guidance
Injury reduction during handling, storage management to limit pathogen-favorable conditions, and targeted chemical control were identified as the primary management approaches. Clean handling and avoidance of mechanical damage reduce inoculation opportunity.

Why This Source Matters
This dissertation provides a systematic pathological survey of dahlia tuber rot from isolation through pathogenicity confirmation and management testing. For growers, the central finding, that Sclerotium rolfsii was particularly destructive and that wound sites were primary entry points, reinforces that mechanical damage during lifting, division, and storage is not just a cosmetic concern. Every cut and bruise is a potential infection site.

Publication Type
Experimental Research Article

Full Citation
Pikovskyi, M. Y., Kolesnichenko, O. V., Melnyk, V. I., & Serediuk, O. O. (2019). Parasitism of micromycete Sclerotinia sclerotiorum (Lib.) de Bary on the dahlia plants (Dahlia Cav.) under different weather conditions. Biological Resources and Nature Management, 11(3–4), 16–24.

Study System
Dahlia plants affected by Sclerotinia sclerotiorum under natural infection conditions; field monitoring in dahlia plantings in Kyiv, Ukraine, 2015 to 2017.

Experimental Context
Field phytopathological monitoring of white mold development on dahlia plants across three vegetation periods under varying weather conditions.

Experimental Design
Stationary plots were inspected every ten days. Disease spread was calculated as appearance frequency. Disease development was evaluated on a six-point severity scale based on stem lesion length, mycelium presence, sclerotia formation, stem circumference affected, lateral shoot symptoms, wilting, cracking, and plant death. Hydrothermal coefficient was calculated from precipitation and temperature data.

Key Results
Stem white mold was detected on dahlia plants across all three monitored seasons. Symptoms included wet, moisture-saturated spots on stems, white mycelium under humid conditions, black sclerotia on stem surfaces and inside infected stems and floriferous shoots, tissue discoloration under drier conditions, tissue maceration, stem and shoot cracking, plant wilting, and bud and flower drying. Disease appeared during autumn vegetation during mass flowering. Initial appearance timing varied with hydrothermal conditions, from the first decade of September in drier seasons to the first decade of October in wetter ones. Maximum spread and development occurred when precipitation continued from the second decade of September through the end of October with no low-temperature interruption. Tubers were infected when lower plant parts were affected.

Mechanistic Insight
Disease spread and development were associated with meteorological conditions. The authors concluded that maximum disease expression was conditioned by extended autumn precipitation combined with the absence of low temperatures during that period. Stem colonization caused stem death even at low disease development ratings. Tuber infection occurred as a downstream consequence of severe stem colonization in lower plant parts.

Practical Guidance
The timing of white mold appearance on dahlia should be considered when planning protective measures. The authors recommended further analysis of weather-factor effects on disease development as a basis for predictive modeling. Growers in regions with warm, wet autumns face elevated Sclerotinia risk during the period of mass flowering.

Why This Source Matters
This study documents Sclerotinia white mold as a recurring field-season pathogen in dahlia, with a clear connection to autumn weather patterns. The finding that tuber infection occurs as a consequence of lower-stem colonization is directly relevant to storage: tubers lifted from plants with active Sclerotinia infections may carry pathogen structures, including mycelium or sclerotia, into storage. For growers, this is a reminder that storage rot sometimes originates in the field before lifting, not in the storage environment itself.

Publication Type
Experimental Research Article

Full Citation
Vlad, I., Vlad, M., & Vlad, I. (2017). Actual fitosanitary problems of cultivated dahlia plants and of tuberous roots stored over winter. Annals of the University of Oradea, Fascicle: Environmental Protection, 29, 127–132.

Study System
Cultivated dahlia plants and tuberous roots stored over winter; greenhouse production using overwinter-stored tuberous roots.

Experimental Context
Greenhouse production in Sîntandrei, Bihor County, Romania, using overwinter-stored tuberous roots planted in March. Disease attack was measured across five treatment variants on 100 plants per variant.

Experimental Design
Five treatment variants were tested across 40 m² plots: thermal substrate disinfection at 90°C for 10 minutes; foliar treatment with Benlate 0.1%; substrate disinfection with 5% formaldehyde; crop rotation; and untreated control. Disease attack was measured as number and percentage of attacked plants.

Key Results
Thermal substrate disinfection at 90°C for 10 minutes reduced disease attack to 5 plants out of 100. Foliar treatment with Benlate 0.1% reduced attack to 30 plants out of 100. Substrate disinfection with 5% formaldehyde reduced attack to 40 plants out of 100. Crop rotation reduced attack to 50 plants out of 100. Untreated plants showed 97 attacked plants out of 100.

Mechanistic Insight
Dahlia diseases in this study were attributed to fungi, bacteria, and viruses together. The paper emphasizes latent infection in tuberous roots, symptom masking in virus carriers, possible bacterial movement into tuberous roots, and abnormal shoot proliferation consistent with cytokinin-like effects. The high disease incidence in untreated controls reflects accumulated inoculum in substrate and planting stock.

Practical Guidance
Preventive sanitation, clean substrate preparation, health monitoring, removal of visibly diseased plants, and laboratory testing during periods of symptom latency are the primary management tools supported by this study. Chemical treatments referenced in the source reflect historical practice and should not be treated as current recommendations.

Why This Source Matters
This study frames dahlia disease not as an isolated event but as a cumulative sanitation problem. The near-total disease incidence in untreated controls, 97 out of 100 plants attacked, illustrates how quickly pathogen load builds in the absence of active management. For growers, the practical message is that disease pressure in dahlia production is not a question of whether pathogens are present but of whether sanitation, substrate management, and stock health are sufficient to suppress them.

Publication Type
Technical Report

Full Citation
Van Leeuwen, P. J., & Trompert, J. P. T. (2005). Onderzoek naar oorzaak van ploffers in Dahlia: De invloed van knolrijpheid, minerale samenstelling, en teelt-, bewaar- en oplegomstandigheden op het optreden van ploffers [Investigation of the causes of “poppers” in dahlia: Effects of tuber maturity, mineral composition, and cultivation, storage, and potting conditions] (Report No. 330793). Praktijkonderzoek Plant & Omgeving.

Study System
Dahlia cuttings and tubers from commercial production lots with high losses from ploffers during cutting production; cultivars ‘Rosella’, ‘Sandra’, ‘Myama Fubuki’, and ‘Stolze von Berlin’.

Experimental Context
Multi-year investigation of wet-rot tuber collapse during cutting production after tubers were laid in greenhouse substrate and temperature was raised to approximately 68 to 72°F (20 to 22°C).

Experimental Design
Three groups of trials tested tuber maturity and drying regime, tuber mineral composition, and cultivation, storage, and potting-up conditions. Additional observations followed a high-ploffer lot handled as potentially infected with Erwinia chrysanthemi. Ploffer percentages, tuber weight, mineral content, and disease incidence were tracked across years and treatments.

Key Results
Tuber maturity and mineral composition trials produced large differences in measured variables but did not produce consistent, reproducible effects on ploffer percentages. Wetter and more humid potting-up conditions promoted ploffers consistently. In a lot approaching 40% ploffers, treating the lot as potentially Erwinia-infected coincided with reduction to 6.5% ploffers in the following year. Erwinia chrysanthemi was detected in a portion of the ploffers and in tubers from plants showing wilting symptoms.

Mechanistic Insight
The report concluded that tuber maturity, mineral composition, cultivation conditions, and storage conditions sometimes influenced ploffer percentages but did not appear to be the primary cause. Wetter potting-up conditions consistently increased ploffers. The final conclusion identified Erwinia chrysanthemi as the very probable cause, while noting that further confirmatory testing was needed.

Practical Guidance
Managing lots as potentially Erwinia-affected, taking later cuttings, removing wilting plants in the field, and avoiding wet potting-up conditions coincided with substantial reduction in losses. These handling adjustments do not require confirmed diagnosis to be worth implementing in high-risk lots.

Why This Source Matters
This report is the foundational Dutch investigation into the ploffers problem, translated here as “poppers”: a specific dahlia tuber-collapse disorder documented in commercial production research. Its significance lies partly in what it ruled out, including tuber maturity and mineral nutrition, which were leading candidate explanations at the time, and partly in what it identified as the probable cause. The convergence of detection data and disease-management response around Erwinia chrysanthemi set the direction for subsequent research. For growers and producers, the report’s most transferable finding may be the simplest one: wet conditions during potting-up increase collapse risk, regardless of the precise causal mechanism.

Publication Type
Trade / Extension Article

Full Citation
Van Leeuwen, P. J., & Trompert, J. P. T. (2006). Erwinia chrysanthemi ook bij ploffers in dahlia boosdoener [Erwinia chrysanthemi also implicated as the cause of “poppers” in dahlia]. BloembollenVisie, 4(97), 20–21.

Study System
Cultivated dahlia tubers and cuttings in greenhouse propagation and field production.

Experimental Context
Pathogen inoculation experiments and symptom observation following the 2005 investigation that identified Erwinia chrysanthemi as the probable cause of poppers.

Experimental Design
Pathogen inoculation experiments with symptom observation and re-isolation; cultivar comparison for susceptibility differences.

Key Results
Erwinia chrysanthemi was confirmed as the causal agent of tuber ploffers and stem wilting in the tested dahlia material. Cultivar susceptibility varied. Latent bacterial infection remained symptomless and caused tuber collapse under warm forcing conditions.

Mechanistic Insight
Bacterial infection remains latent in tuber tissue and is activated by the warm, moist conditions of greenhouse forcing. The transition from symptomless infection to visible collapse is triggered by environmental conditions rather than by pathogen arrival at that point.

Practical Guidance
Clean starting material, propagation sanitation, temperature management during forcing, and cultivar selection for lower susceptibility all reduce poppers risk.

Why This Source Matters
This article confirmed what the 2005 report could only identify as probable: Erwinia chrysanthemi was implicated as the causal agent behind dahlia ploffers, translated in the citation as “poppers.” The confirmation of latent infection is the central practical insight. Bacteria could be present in apparently healthy tubers and remain undetectable until forcing conditions triggered collapse. That finding explains why visual inspection before storage or forcing cannot reliably identify affected material, and why propagation hygiene and stock origin matter more than what tubers look like at planting time.

Publication Type
Trade Journal Article

Full Citation
Van Leeuwen, P. J., Dees, R. H. L., Vreeburg, P. J. M., & van Doorn, J. (2012). Oorzaak Erwiniaproblemen dahlia vooral Dickeya dianthicola [Cause of Erwinia problems in dahlia primarily Dickeya dianthicola]. BloembollenVisie, 2012(246), 22–23.

Study System
Cultivated dahlia in commercial propagation and field production.

Experimental Context
Field monitoring of propagation chains, PCR diagnostics, hygiene assessments, and artificial inoculation trials to identify the specific bacterial species responsible for Erwinia problems in commercial dahlia.

Experimental Design
Field monitoring of propagation chains with PCR-based pathogen identification; hygiene assessments of propagation practices; artificial inoculation trials to confirm pathogenicity.

Key Results
Dickeya dianthicola was identified as the primary causal organism of Erwinia-associated problems in commercial dahlia production, including wilting and tuber ploffers. Infection increased in later cuttings taken from the same stock. Latent tuber infections were common. Mowing equipment was demonstrated as a transmission route in the field.

Mechanistic Insight
Dickeya dianthicola is host-specifically pathogenic in dahlia. Latent infection and mechanical spread through propagation tools and field equipment govern disease expression more than environmental conditions alone. Each successive cutting cycle from infected stock increases the bacterial load carried into the propagation chain.

Practical Guidance
Hygiene in propagation, disinfection of cutting and mowing equipment, disease-free tissue culture starts, and careful water management all reduce Dickeya risk. Taking fewer cutting cycles from stock plants and starting from pathogen-tested material limits cumulative infection buildup.

Why This Source Matters
This study refined the bacterial identity question that KC-0517 and KC-0418 had established around Erwinia chrysanthemi. Taxonomy of soft-rot bacteria in this group has been revised substantially since the early poppers research, and Dickeya dianthicola is now recognized as the primary agent in this dahlia context. The mowing equipment finding is the most practically significant result for field growers: a piece of equipment running through an infected planting can spread Dickeya to healthy plants without any obvious indication of transmission occurring.

Publication Type
Research Report

Full Citation
Van Doorn, J., Vreeburg, P. J. M., & Van Leeuwen, P. J. (2008). Beheersing van Erwinia in bolgewassen: agressief snot en witsnot in hyacint, Zantedeschia, dahlia en andere bloembolgewassen [Control of Erwinia in bulb crops: aggressive soft rot and white rot in hyacinth, Zantedeschia, dahlia, and other bulbous crops]. Praktijkonderzoek Plant & Omgeving.

Study System
Bulbous ornamental crops including hyacinth, Zantedeschia, dahlia, and others; field, harvest, processing, storage, and propagation chain contexts.

Experimental Context
Survey, diagnostics, bioassays, inoculation trials, and field experiments across the ornamental bulb crop sector, with dahlia included as one of the affected crops.

Experimental Design
Culture, ELISA, and PCR diagnostics applied to affected material; bioassays and inoculation trials to characterize pathogen behavior; field trials to evaluate risk factors and management responses.

Key Results
Erwinia chrysanthemi, Dickeya spp., and Pectobacterium carotovorum were frequently associated with soft rot across the bulb crop sector. Dahlia ploffers were linked to Erwinia chrysanthemi. Damage, moisture, and temperature were identified as key risk factors across crops. Mechanical spread dominated transmission pathways.

Mechanistic Insight
Soft rot in bulb crops requires sufficient bacterial load combined with tissue damage and favorable moisture and temperature conditions. Mechanical spread through processing, propagation, and field equipment is the primary transmission pathway rather than soil-borne or airborne dispersal.

Practical Guidance
Hygiene throughout the production chain, damage reduction at harvest and processing, rapid drying after lifting, temperature control during storage and forcing, avoidance of washing practices that spread bacteria in water, and targeted diagnostics all reduce soft-rot risk across bulb crops including dahlia.

Why This Source Matters
This report is included as dahlia-including bulb-crop evidence, not dahlia-exclusive research. Its value for the dahlia context is the broader mechanistic picture it provides: the conditions that govern soft-rot development in dahlia are not unique to dahlia but are shared across a range of ornamental storage organs. The risk-factor framework, bacterial load, tissue damage, moisture, and temperature, applies directly to how dahlia growers should think about postharvest handling, storage environment, and propagation-chain hygiene.

Publication Type

Technical Research Report

Full Citation

Van Leeuwen, P. J., & Trompert, J. P. T. (2009). Ontwikkelen van een praktische toets op Erwinia bij Dahlia (ploffers) [Development of a practical diagnostic test for Erwinia in dahlia (“poppers”)] (Project No. 32 360433 00). Praktijkonderzoek Plant & Omgeving.

Study System
Dahlia tubers in commercial cutting production.

Experimental Context
Applied diagnostic testing for bacterial ploffers under commercial horticultural conditions, following the establishment of Erwinia chrysanthemi as the probable causal agent.

Experimental Design
Warm, moist incubation tests were applied to tuber lots and compared with actual ploffer incidence during forcing; bacterial identification of rotting tubers was conducted during testing.

Key Results
Test-induced rot did not reliably predict ploffer incidence during subsequent cutting production. Non-Erwinia bacteria caused false positives under the warm, moist incubation conditions.

Mechanistic Insight
Ploffer development under commercial forcing conditions is not specifically triggered by the same stress response that the incubation test induces. The test conditions selected for general soft-rot susceptibility rather than Erwinia-specific pathogenicity, producing results that did not correspond to commercial outcomes.

Practical Guidance
The proposed warm, moist incubation test was found unsuitable for practical screening of dahlia lots before cutting production. Sanitation protocols and clean stock are more reliable preventive measures than pre-production screening with this method.

Why This Source Matters
The attempt to develop a practical diagnostic test is itself informative. It shows how difficult it is to design a quick, reliable screen for a pathogen that behaves differently under incubation stress than under commercial forcing conditions. For growers considering whether a field test or home-scale rotting trial can predict which tubers will collapse in forcing, this research gives a clear caution. The biology of latent Erwinia infection in dahlia does not lend itself to that kind of simple prediction.

Publication Type

Trade Journal Article

Full Citation

Van Leeuwen, P. J., & Trompert, J. P. T. (2009). Praktische toets voor ploffers in dahlia werkt onvoldoende [Practical test for “poppers” in dahlia proves inadequate]. BloembollenVisie, 2009(181), 20.

Publication Type
Trade Journal Article

Full Citation
Van Leeuwen, P. J., & Trompert, J. P. T. (2009). Praktische toets voor ploffers in dahlia werkt onvoldoende [Practical test for “poppers” in dahlia proves inadequate]. BloembollenVisie, 2009(181), 20.

https://scholar.google.com/scholar?q=praktische+toets+ploffers+dahlia+werkt+onvoldoende+Van+Leeuwen+Trompert+2009+BloembollenVisie

Study System
Dahlia tubers in commercial cutting production and postharvest disease screening.

Experimental Context
Evaluation of a warm, humid incubation test as a practical pre-production screen for poppers, published as a trade communication of the findings reported more fully in KC-0419.

Experimental Design
Warm, humid incubation test applied to commercial lots and compared with actual ploffer outcomes during cutting production.

Key Results
Test results did not consistently predict ploffers during cutting production. The test identified soft-rot susceptibility under stress conditions but not Erwinia-specific infection.

Mechanistic Insight
Soft-rot symptom expression under applied stress does not reliably indicate Erwinia infection or predict commercial ploffer incidence.

Practical Guidance
Do not rely on warm, humid incubation tests as a pre-production screen for poppers. Prioritize bacterium-free planting material and rigorous propagation hygiene as the primary prevention strategy.

Why This Source Matters
This trade article communicates the same findings as KC-0419 to a practitioner audience and is included here because it reached a different readership than the technical report. Together, KC-0419 and KC-0429 represent the research and practitioner-facing publications from the same investigative work: a paired record of a diagnostic approach that was tested, found unreliable for practical prediction, and publicly reported as such. That transparency is itself part of the scientific record on dahlia ploffers.

Publication Type
Conference Proceedings Paper

Full Citation
Lemattre, M., & Lemattre, P. (1980). Production of Erwinia free stocks of dahlia in France. Acta Horticulturae, 109, 529–533.

Study System
Dahlia vegetatively propagated tubers and cuttings; detection of Erwinia chrysanthemi in asymptomatic cuttings during glasshouse propagation.

Experimental Context
Evaluation of detection methods for Erwinia chrysanthemi in symptomless dahlia cuttings from 37 cultivars, with the aim of developing a practical routine for producing bacteria-free propagation material.

Experimental Design
Approximately 600 symptomless cuttings from 37 cultivars were tested using three detection methods applied to basal stem segments: isolation on YPDA and King B agar plates; immunofluorescence staining with anti-serum; histofluorescence microscopy in blue light. Methods were compared for diagnostic performance and suitability for routine commercial use.

Key Results
Isolation on YPDA allowed diagnosis within two days and provided clear differentiation of infected samples. Immunofluorescence staining sometimes produced difficult identification due to cross reactions and fluorescent cell walls. Histofluorescence allowed observation of infected vascular vessels. Isolation on YPDA was determined to be the most practical routine diagnostic method and produced effective results over two years of commercial application.

Mechanistic Insight
Erwinia chrysanthemi spreads primarily through propagation of symptomless infected cuttings produced from infected tubers. The bacterium colonizes vascular tissues and is detectable through culture-based isolation and fluorescence-based visualization of infected vessels before visual symptoms appear in the cutting.

Practical Guidance
Routine isolation of basal stem fragments on YPDA medium provides a reliable and economical method for detecting Erwinia-infected cuttings and enabling production of bacteria-free propagation material. The method is practical for commercial scale and does not require advanced laboratory infrastructure.

Why This Source Matters
This study is among the earliest systematic approaches to breaking the cycle of Erwinia transmission through dahlia propagation chains. Its central finding, that symptomless cuttings can be screened and infected material removed before it enters the propagation cycle, established the principle that clean stock production in dahlia is achievable through routine diagnostic monitoring. For growers and producers who rely on vegetative propagation, this is the research foundation behind the recommendation to start from tested, certified, or tissue-culture-originated material whenever Erwinia pressure is a concern.

Publication Type
Journal Article

Full Citation
Bruton, B. D. (1994). Mechanical injury and latent infections leading to postharvest decay. HortScience, 29(7), 747–749.

Study System
Fruits and vegetables; postharvest disease development linked to mechanical injury and latent infection across horticultural crops.

Experimental Context
Literature synthesis of infection pathways, host responses, and control strategies in postharvest pathology.

Experimental Design
Narrative review of experimental literature on wound-facilitated pathogen entry, latent infection mechanisms, and management approaches.

Key Results
Wound and latent infections are major drivers of postharvest decay across horticultural crops. Mechanical injury increases pathogen entry and activates latent infections. Cell wall degradation by pectolytic enzymes and calcium-mediated wall stability govern decay progression.

Mechanistic Insight
Mechanical injury disrupts the physical barrier that excludes pathogens and can activate latently present organisms that would otherwise remain quiescent. Pectolytic enzyme activity is central to tissue breakdown once pathogen entry has occurred. Calcium status of host tissue influences cell wall integrity and resistance to enzymatic degradation.

Practical Guidance
Minimizing mechanical injury, managing storage conditions, and maintaining adequate calcium status in crop tissue reduce postharvest decay risk. These principles apply broadly across horticultural crops where wound entry and latent infection are operative.

Why This Source Matters
This review is included as general postharvest pathology support, not as dahlia-direct evidence. Its contribution here is mechanistic: it articulates the principles of wound-facilitated pathogen entry and latent infection activation that the dahlia-specific sources in this cluster document in practice. The latent-infection behavior established for dahlia by KC-0749 and KC-0441, bacteria present in symptomless tissue and activated by conditions rather than by new infection events, is consistent with the broader postharvest pathology framework this review describes. The review does not prove these mechanisms apply specifically to dahlia; the dahlia-direct sources establish that. It provides the mechanistic vocabulary for understanding why they occur.

The Knowledge Card summaries in this collection were written by the author based on direct reading of the cited sources. AI tools assisted with retrieval, formatting, and assembly of this collection from the Dahlia Doctor research archive. All curatorial decisions, including source selection, topic organization, and editorial framing, were made by the author.