Postharvest Pathology of Fresh Horticultural Produce

Lluís Palou, Joseph L. Smilanick, Lluís Palou, Joseph L. Smilanick

• Publisher: CRC Press
• Year: 2019
• Print ISBN: 9781138630833
• eBook ISBN: 9781351805889
• Edition: 1
• Topic: Technology & Engineering
• Subtopic: Food Science
• Index: Technology & Engineering

Optimal distribution of fresh horticultural products entails prolonging their freshness and nutritional quality as long as possible after harvest. A major limitation to their marketing is decay after harvest, which is caused primarily by fungal pathogens. Postharvest Pathology of Fresh Horticultural Produce provides a comprehensive resource of information about the biology and control of postharvest diseases of many fresh horticultural products, citing sources from appropriate literature of any age, rather than only the most recent.

The etiology and symptoms of postharvest diseases and the biology of postharvest pathogens are reviewed by leading experts, who are familiar with many of world's most popular fresh fruits and vegetables and the diseases that affect them.

Key aspects related to infection and epidemiology, methods to minimize postharvest decay losses, including use of conventional fungicides and alternative management strategies, harvest and handling practices, and other aspects are described for the most significant temperate, subtropical, and tropical fruits as well as fruit-like vegetables and leafy vegetables.

Features:

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• Provides comprehensive academic and practical reviews of postharvest diseases of fresh fruits and vegetables

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• Discusses the economic importance, etiology, and epidemiology of the most significant postharvest diseases

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• Includes quality color plates that allow the practical identification of disease symptoms

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• Explains practical postharvest disease management actions, including the use of conventional fungicides and alternatives to their use

The authors summarize a massive quantity of published information, and often apply their own considerable practical experience to identify and interpret the most significant information. This book is a valuable and comprehensive resource for industry professionals, academics, educators, students, consultants, pest control advisors, regulatory personnel, and others interested in this subject.

Section I

POSTHARVEST DISEASES OF FRESH HORTICULTURAL PRODUCE

Chapter 1

Citrus Fruits

Joseph L. Smilanick

Private consultant, formerly USDA-ARS, Kingsburg, CA, USA

Arno Erasmus

Wonderful Citrus, Delano, CA, USA

Lluís Palou

Laboratory of Pathology, Postharvest Technology Center (CTP), Valencian Institute of Agrarian Research (IVIA), Montcada, Valencia, Spain

1 Introduction

2 Diseases from Postharvest Fruit Infection

2.1 Green and Blue Molds

2.2 Sour Rot

2.3 Miscellaneous Diseases

3 Diseases from Preharvest Fruit Infection

3.1 Stem-End Rots

3.2 Anthracnose

3.3 Brown Rot

3.4 Black Rot (Alternaria Rot)

3.5 Miscellaneous Diseases

4 Commercial Disease Management

4.1 Fungicides

4.1.1 Imazalil

4.1.2 Thiabendazole

4.1.3 Pyrimethanil

4.1.4 Fludioxonil

4.1.5 Azoxystrobin

4.1.6 Sodium Ortho-Phenylphenate and Ortho-Phenylphenol

4.1.7 Propiconazole

4.1.8 Potassium Phosphite

4.1.9 Other Active Ingredients

4.2 Application Methods

4.2.1 High-volume Aqueous Applications

4.2.2 Low-Volume Non-Recirculating Spray Applications

4.3 Sanitizing Recirculating Solutions

4.4 Sequence and Combinations of Application Methods and Fungicides

4.5 Factors Further Affecting Fungicide Efficacy

4.5.1 Effective Residue

4.5.2 Infection Age and Fruit Susceptibility

4.5.3 Wound Size and Inoculum Load

4.6 Fungicide Resistance

4.7 Alternatives to Conventional Fungicides

Acknowledgments

References

Abbreviations

2,4-D	2,4-dichlorophenoxyacetic acid
AZX	Azoxystrobin
CFU	Colony forming units
EC	Emulsifiable concentrate
EU	European Union
FAO	Food and Agriculture Organization of the United Nations
FLU	Fludioxonil
FRAC	Fungicide Resistance Action Committee
GRAS	Generally recognized as safe
IMZ	Imazalil
MRL	Maximum residue limit
OPP	Ortho-phenylphenol
PAL	Phenylalanine ammonia-lyase
PAA	Peroxyacetic acid
PCZ	Propiconazole
PYR	Pyrimethanil
ROS	Reactive oxygen species
SOPP	Sodium ortho-phenylphenate
SS	Sulfate salt
TBZ	Thiabendazole
USA	United States of America

1 Introduction

Citrus fruits (Citrus spp., Rutaceae) are among the most important fruits produced for human consumption in the world and rank first in terms of value of international trade. Total worldwide production of fresh citrus exceeded 124 million tons in 2016, according to the following distribution: 67 million tons of oranges (Citrus sinensis L.); 33 million tons of mandarins or tangerines (Citrus reticulata Blanco), including clementines (Citrus clementina hort. ex Tanaka), Satsumas (Citrus unshiu Marcow.), and a variety of hybrid mandarins; 16 million tons of lemons (Citrus limon [L.] Burm. f.) and limes (Citrus aurantiifolia [Christm.]); and 8 million tons of grapefruits (Citrus paradisi Macfad.) (FAO, 2017). In 2016, the most important citrus-producing countries were China, Brazil, India, the United States of America (USA), Spain, Mexico, Egypt, Turkey, Iran, Italy, Argentina, South Africa, and Morocco, among others. In terms of international trade, Spain is the leading country, with 4.1 million tons of exports of fresh produce in 2016 (FAO, 2017).

We interpret postharvest diseases of citrus to be those caused by microbial pathogens that colonize or otherwise harm fruit, and do not include those disorders of physiological or abiotic origin. Most postharvest diseases of citrus fruits are caused by filamentous fungi, and the common names of the diseases they cause are based on the symptoms they produce. They have been classically divided into two groups according to the time when infection predominantly occurs (Eckert and Eaks, 1989). The first group of postharvest diseases is those that initiated when the pathogen infects the fruit before harvest, termed preharvest infections. These infections are called “latent” (when not visible) or “quiescent” (when the inactive infection is visible), and they do not cause significant disease until after harvest. The second group of postharvest diseases is those that initiated when infection occurs just before, during, or after harvest. Most of these pathogens infect through rind wounds and disease progresses immediately after infection. Wound pathogens infect mature fruit through rind injuries or bruises inflicted in the field near harvest or during harvest, postharvest handling in the packinghouse, transportation, or when marketed. In contrast, latent pathogens infect the fruit in the field during the growing season and remain inactive until they resume growth after harvest because of significant changes in the fruit properties and environmental conditions. The relative importance of each type of these diseases varies, but the most important factor is the climate of the citrus-producing area. In typical summer-rainfall production areas, such as Florida, Brazil, or Southeast Asia, diseases from preharvest infections are usually high. In contrast, in areas of sparse summer rainfall or Mediterranean-type climate areas, such as Spain and other Mediterranean countries, California, Australia, and most citrus areas in South Africa, the incidence of postharvest diseases is typically lower and diseases from harvest or postharvest infections, especially green and blue molds caused by Penicillium spp., cause most losses.

Regardless of the climatic area, losses of citrus fruits due to postharvest diseases are quite variable and dependent on the variety, tree age and condition, weather conditions during the growing and harvest season, the extent of physical injury to the fruit during harvest and subsequent operations, pathogen inoculum density, the effectiveness of antifungal treatments, sorting/grading operations after harvest, and the postharvest environment. In a summary of 12 yr of inspections of commercial shipments of California and Florida citrus fruits in the New York produce market, Penicillium decays, sour rot, and stem-end rot were present in 30, 9, and 5%, respectively, of the inspected shipments (Ceponis et al., 1986). In another study in California, the total percentage of fruit lost to decay during both storage and subsequent marketing was about 8% in three lemon packinghouses (Bancroft et al., 1984). Green mold losses in California are typically 2–4% during ethylene degreening, but can exceed 30% in disease-conducive years when heavy rains occur before harvest, or when numerous split fruit or other rind injuries occur and become infected on trees before harvest (Smilanick et al., 2006a). In Spain, Tuset (1987) estimated that Penicillium molds, black rot, gray mold, anthracnose, and sour rot accounted for 55–80, 8–16, 8–15, 2.5–6, and 2–3%, respectively, of total postharvest decay observed in oranges and mandarins during the marketing season. Pelser (1977a) reported that Penicillium molds accounted for about 75% of the decay observed in South African ‘Valencia’ oranges shipped to London. In Florida, among samples of several cultivars of untreated oranges collected over a 5-yr period in this high-rainfall area, stem-end rot was the most common disease, and it infected 13–42% of the fruit after storage at 21°C for 3 wk (Smoot, 1977). The fruit examined in all of these reports were from commercial packinghouses that employed sanitation measures, fungicides, and temperature management regimes to minimize decay; losses among fruit handled without these measures can be much higher. Among smaller growers, especially organic growers and some of those in underdeveloped countries, where efficient transportation, refrigeration, and chemical treatments may be less available, losses are typically much higher and can make export sales infeasible (Kader, 2005).

The percentage of fruit lost to postharvest diseases is only one measure of their economic impact. Citrus postharvest diseases can also cause significant losses for growers, packers, shippers, and consumers by harming future sales. Inspection standard thresholds for decay are low; typically, if the number of decayed fruits exceeds 0.5%, the grade and price of the shipment will be reduced. The unsightly appearance of rotten fruit, although the incidence may be comparatively low, repels wholesale buyers who may as a consequence abandon the affected producer and seek other sources. In addition to the losses of individual fruit, propagules produced from lesions on decaying fruit contaminate the surrounding environment, initiating new cycles of decay, and requiring the remaining healthy fruit to be cleaned and repackaged. If the losses occur after shipment, the producer is usually billed for these added costs, which can exceed their returns (Smilanick et al., 2006a). Furthermore, the loss of one piece of fruit after harvest can be more than twice as costly as the loss of one before harvest since expenses that begin at harvest typically surpass those to produce the fruit. For example, between 51 and 67% of the total cost of growing, harvesting, packing, marketing, and shipping California oranges and lemons occurred after the fruit were harvested (Eckert and Eaks, 1989).

The ubiquitous occurrence of virulent and aggressive pathogens, the employment of relatively warm storage conditions to avoid chilling injury (but favor rapid pathogen growth), and minimal resistance of citrus fruits to infection make management of postharvest diseases of paramount importance for producers and marketers of citrus fruits, particularly if export sales or long-term storage are employed. In this chapter, the major diseases and actions to manage them will be described.

2 Diseases from Postharvest Fruit Infection

2.1 Green and Blue Molds

Green mold, caused by Penicillium digitatum (Pers.: Fr.) Sacc., is the most important postharvest disease of citrus fruits produced in areas with a Mediterranean-type climate, characterized by scant summer rainfall. Blue mold, caused by Penicillium italicum Wehmer, is typically of lesser overall importance since it grows slower than P. digitatum at ambient temperatures, but may become the major problem under certain conditions. Penicillium molds are also important in production areas with abundant summer rainfall, where the total incidence of postharvest decay is higher and diseases caused by preharvest fruit infections are predominant (Eckert and Eaks, 1989; Palou, 2014). A third Penicillium sp., Penicillium ulaiense H.M. Hsieh, H.J. Su & Tzean, the cause of whisker mold, was first found in California in mixed infections with P. digitatum in stored citrus fruits (Holmes et al., 1994). It resembl...

Table of contents

• Cover
• Half Title
• Title Page
• Copyright Page
• Table of Contents
• PREFACE
• EDITOR BIOGRAPHY
• LIST OF CONTRIBUTORS
• Section I: Postharvest Diseases of Fresh Horticultural Produce
• Section II: General Aspects of Infection Causing Postharvest Disease
• Section III: Novel Technologies to Control Postharvest Decay of Fruits and Vegetables
• INDEX