Post Harvest Management of the Pests and Some Important Diseases of the Fruits

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1 See discussions, stats, and author profiles for this publication at: Post Harvest Management of the Pests and Some Important Diseases of the Fruits CHAPTER JANUARY 2015 READS AUTHORS: Sadegh Mohajer University of Malaya 42 PUBLICATIONS 44 CITATIONS Rosna Mat Taha University of Malaya 154 PUBLICATIONS 329 CITATIONS SEE PROFILE SEE PROFILE Jamilah Syafawati Yaacob University of Malaya 22 PUBLICATIONS 27 CITATIONS Aloka Kumari University of kwazulu Natal,Pietermaritzburg 41 PUBLICATIONS 17 CITATIONS SEE PROFILE SEE PROFILE Available from: Aloka Kumari Retrieved on: 21 December 2015

2 Post Harvest Management of the Pests and Some Important Post Harvest Management of the Pests and Some Important Diseases of the Fruits Sadegh Mohajer 1 *, Rosna Mat Taha 1, Jamilah Syafawati Yaacob 1 and Aloka Kumari 2 ABSTRACT A wide variety of fungal and bacterial pathogens cause post-harvest disease in fruits and vegetables. Some of these infect produce before harvest and then remain quiescent until conditions are more favourable for disease development after harvest. Other pathogens infect produce 1 Institute of Biological Sciences, Faculty of Science, University of Malaya, Kuala Lumpur, Malaysia. 2 School of Life Sciences, RCPGD, University of KwaZulu-Natal, Pietermaritzburg, S. Africa. * Corresponding Author: mohajer.ae@gmail.com

3 2 Recent Trends in Post Harvest Technology and Management during and after harvest through surface injuries. In the development of strategies for post-harvest disease control, it is imperative to take a step back and consider the production and post-harvest handling systems in their entirety. Traditionally fungicides have played a central role in postharvest disease control. However, trends towards reduced chemical usage in horticulture are forcing the development of new strategies. This provides an exciting challenge for the 21 st century. The objectives of this chapter are: i) to maintain the good quality of the produce grown so that the produce can be competitive in the various market places i.e. local or overseas; and ii) to reduce loss in quantity or volume and in the qualitative or nutritive value of the produce. Keywords:Fungicides, Post-harvest Management, Bacterial Pathogens, Disease control INTRODUCTION In the past three decades, many countries in Asia have promoted horticulture and export market development to increase the income of farmers as they diversify from cereal cropping. Mango and banana are important crops in much of tropical and subtropical Asia, providing income and nutrition through fresh and processed product. However, their intrinsic short shelf life and susceptibility to fruit rots reduce marketability and profits. Post-harvest decay is still a serious problem in the storage of many fresh fruits and vegetables, especially acidic, succulent and nutritious fruits and vegetables that suffer from rotting diseases (Philips, 1984; Moss, 2008). On average, 40% of fresh fruit and vegetables are lost to post-harvest disease (Irtwange, 2006), and such losses in China have been estimated as 4.5 billion US dollar per year (Hu and Zhang, 2007). Controlling or reducing disease relies on integrated crop and postharvest management, with attention to fungicide application, crop hygiene and nutrition, and the management of ripening, to optimise advantages conferred by the plant's natural resistance factors that prevent and delay disease development.agricultural production and food distribution systems have evolved over many years to a complex system which allows for nearly year-round supply of most fresh commodities through longterm storage and long-distance shipments to consumers. The expectation of year-round supplies has resulted in increased challenges for post-harvest handling systems. The availability of fungicides for disease management likely played a major role in the evolution of our current system of food distribution. With the recent loss of registration of many post-harvest

4 Post Harvest Management of the Pests and Some Important... fungicides and more expected under the Food Quality Protection Act (FQPA), as well as consumer pressure to reduce the amount of chemicals used on food, the challenge to maintain our current system of food distribution increases (Mitcham, 1999). Pest Management The fresh produce industry must begin to place increased emphasis on other methods of pest management. Integrated post-harvest(ipm) is a system approach towards pest management where good management practices are combined with one or more contributory treatments to result in an acceptable level of disease and insect control. A successful IPM system requires a higher degree of involvement with the post-harvest handling process including close observation and attention to details. Decisions on pest management strategies are made as a result of those observations (Mitcham, 1999). The ability of the pest to infest the host depends on the effectiveness of its mechanisms of invasion. In many ways, the pest is dependent on the host's susceptibility and environmental factors. The development of a pest infestation depends on favourable conditions in the environment, the host and the pest. By manipulation of one of these three factors, we can reduce the level of pest problems. The host's suitability for pest infestation can depend on natural resistance, cultural practices, or the presence of wounds. The environment can be manipulated easily after harvest to provide a temperature or an atmosphere that is unfavourable to pests and favourable to the host (Mitcham, 1999). Identification of the Pathogen Correct identification of the pathogen causing post-harvest disease is central to the selection of an appropriate disease control strategy. Many of the fungi which cause post-harvest disease belong to the phylum Ascomycota and the associated Fungi Anamorphici (Fungi Imperfecti) pathogen inhibition is greater when the antagonist is applied prior to infection taking place (Coates and Johnson, 1997) The genera Phgtophthora and Pgtttium are important post-harvest pathogens, causing a number of diseases such as brown rot in citrus (Phgtophthora citrophthora and P. parasitica) and cottony leak of cucurbits (Pgthium spp.). Rhizopus and Mucor are important genera of post-harves pathogens in the Phylum zygornycota. Rhizopus stolonifer is a common wound pathogen of a very wide range of fruits and vegetables, causing a rapidly spreading watery 3

5 4 Recent Trends in Post Harvest Technology and Management soft rot. Genera within the Phylum basidiomycota are generally not important causal agents of post-harvest disease, although fungi such as Sclerotium rolfsiiand and Rhizoctonia solanr, which have basidiomycete sexual stages, can causesignificant post-harvest losses of vegetable crops such as tomato and potato. The major causal agents of bacterial soft rots are various species of Ertuinia, Pseudomonas, Bacittus, LactobaciLLus and Xanthomonas. Bacterial soft rots are very important post-harvest diseases of many vegetables, although they are generally of less importance in most fruits. This is because most fruits have a low ph which is inhibitory to the majority of bacterial plant pathogens. Biological Control In recent years, there has been considerable interest in the use of antagonistic microorganisms for the control of post-harvest diseases. Such organisms can be isolated from a variety of sources including fermented food products and the surfaces of leaves, fruits and vegetables. Once isolated, organisms (whether they be bacteria, yeasts or filamentous fungi) can be screened in various ways for inhibition of selected pathogens. In the most reported cases, pathogen inhibition is greater when the antagonist is applied prior to infection taking place (Coates and Johnson, 1997). In Australia, only field applications of a non-antibiotic producing strain of Bacillus sp. have shown potential for the control of anthracnose in avocado. There are a number of reports in the literature concerning the biological control of wound pathogens in various fruits and vegetables. To be effective against wound pathogens, an antagonist must be able to successfully colonise wound sites to the exclusion of the pathogen. Lise Korsten's group has the longest history in this area, and they have focussed on using a gram positive bacterium, Bacillus licheniformis, that resists desiccation and is food safe. In general, minor reductions in disease occur at 10 ºC and 25 ºC, either alone or in combination with fungicides (Govender and Korsten, 2006). Although less publicized, significant reductions have also occurred with Gram negative bacteria and other amendments (Vivekananthana et al., 2004). Fungicides Control The benzimidazoles are still effective role as post-harvest treatments, although benomyl's registration has been cancelled (Ploetz, 2008). Thiabendazole (TBZ) is almost as effective as benomyl (benomyl's

6 Post Harvest Management of the Pests and Some Important... formulation enables superior host penetration, a greater spectrum of acitivity, and great efficacy), and it has a post-harvest residue tolerance in the USA. As mentioned above, prochloraz and imazilil have been used as post-harvest treatments in others countries but are not labelled for the US market. Although a non-specified strobilurin was tested in combination with a biocontrol agent for post-harvest anthracnose control in South Africa, it was not tested alone (Govender and Korsten, 2006). Non-Fungicidal Measures Since there is a close relationship between ripening and the development of post-harvest disease, post-harvest disease development can be managed indirectly by delaying the onset, and reducing the rate of ripening (Prusky and Keen, 1993). As a climacteric fruit, mango undergoes profound biochemical changes as it ripens. Ripening is a process in fruit senescence that is associated with and enhanced by increased ethylene production (Brecht and Yahia, 2009; Snowdon, 1990). Ripening can also be inhibited by modified atmosphere (MA) storage (usually reductions in O 2 levels and increased CO 2 ) (Brecht and Yahia, 2009). Some work has been conducted on the impact of MA on post-harvest disease. For example, when fruit were exposed to an atmosphere containing 30% CO 2 for 24 h, researchers reported an increase in the concentrations of antifungal compounds in fruit and consequently less disease when these fruits ripened (Prusky et al., 2009). Heat Control Hot water, vapour heat and forced hot air are post-harvest treatments for fruit flies, which are quarantine pests for fruit in much of the world (Jacobi et al., 2001). The Mediterranean fruit fly, Ceratitis capitata, and the Mexican fruit fly and related species, Anastrepha spp., must be controlled in mangos produced in tropical America that will be sold in the US (McGuire, 1991). Hot water, the most common of these treatments, is economical, reliable and can be used with other commodities (Jacobi et al., 2001). The times and temperatures that are needed to achieve prescribed lethal levels depends of the size and shape of the fruit that are treated. There is variation among different cultivars for heat tolerance. Jacobi et al. (2001) reviewed the requirements and heat tolerances of different cultivars and the symptoms that are associated with heat damage. An added benefit of heat treatment to satisfy insect quarantines is its reduction of anthracnose and other post-harvest decays (McGuire, 1991). 5

7 6 Recent Trends in Post Harvest Technology and Management Natural Fungicides Many compounds produced naturally by microorganisms and plants have fungicidal properties. Chitosan, for example, is not only an elicitor of host defence responses but also has direct fungicidal action against a range of pathogens (Coates and Johnson, 1997). Antibiotics produced by various species of Trichoder"RNA" have potent antifungal activity against Botrgtis ctnerea, Sclerotinta sclerottorum, Cortictum roljsti and other important plant pathogens. There are many other natural compounds which have been isolated and shown to possess considerable antifungal activity. Although these compounds may be more desirable than synthetic chemicals from a consumer viewpoint, their potential toxicity to humans needs to be evaluated before useable products are developed. Post-Harvest Diseases of Apple and Pear Post-harvest diseases of apple and pear fall into three general categories: Blossom Infections A number of fungi cause fruit infection by first colonizing or infecting the blossoms. The incidence of infection is much more prevalent in a wet spring. There are often no visible symptoms of disease until after harvest. In some cases infected fruit may colour and fall prematurely in the orchard. The spores of these fungi are prevalent in the ground litter and in the tree. Therefore, mowing and clearing of leaves, fallen fruits and prunings can help reduce potential sources of infection. These fungal pathogens can be reduced with spring sprays. Although there are no chemicals registered specifically for these fungi, carefully selected scab fungicides at the pink to petal-fall stages will provide some control. See table below for more information. Fall lenticel Infections Several fungi can enter the fruit through weak lenticels and wounds, and may not show symptoms until after a period of storage. Cleaning up the cankers in the trees is the most effective control for Bull's Eye and Phacidiopycnis rot. Since snow mold rot has been associated with soil and grasses or weeds being transferred from the orchard floor to the bin, careful handling of bins in the orchard should help reduce this problem. There are no fungicides registered specifically for these diseases.

8 Post Harvest Management of the Pests and Some Important... Some pin point scab sprays will reduce the incidence of these diseases in storage. Anthracnose in Mango and Banana The key diseases are anthracnose in mango and banana, caused by Colletotrichum gloeosporioides and C. musae, respectively, and stem-end rot in mango, cause by fungi in the family Botryosphaeriaceae (Neofusicoccum spp., Lasiodiplodia theobromae etc.).a significant component was the identification and evaluation of activators of plant defences under field conditions. The activators were known resistanceinducing agents, including acibenzolar-s-methyl (Bion), and elicitors derived from fungal pathogens (in banana). Another component was to characterise some of the key biochemical defences contributing to the resistance, and to identify treatments, varietal properties or other agronomic practices that may influence their relative effectiveness (Johnson, 2007). The Causal Agents of Avocado Fruit Diseases The most serious diseases of avocado fruit are all caused by fungi. In Australia,anthracnose is predominantly caused by the fungus Colletotrichum gloeosporioides, although C. acutatum is a minor causal agent of the disease. Although symptoms ofanthracnose do not normally appear in "Hass" fruit until ripening, the initial stages of infection by the pathogen actually occur in the field on developing fruit. Once the fungus penetrates the outer skin layer of fruit, it remains there in a dormant or'quiescent' state until changes occur in the fruit skin which allows infection to proceed (Coates et al., 2001). In particular, changes in theconcentration of antifungal compounds called 'dienes' are thought to be important in the regulation of anthracnose quiescence in avocado (Prusky, 1996). One theory states that the fungi occurs "endophytes" in avocado stem tissue, then graduallycolonising inflorescences, fruit pedicels and fruit stemend tissue are inoculated. Evidence for this mode of infection has been found in the case of mango stem-end rot (Johnson etal., 1992). Another theory is that spores of the stem-end rot fungi infect avocado at flowering, eventually leading to colonisation of the fruit stem-end tissue. A third possible mode of infection for the stem-end rot fungi is at harvest time via the freshly cut surface of the fruit (Everett, 1999). Colletotrichum gloeosporioides has been shown to cause pepperspot (Willingham et al. 2000).Cercospora spot caused by Pseudocercospora 7

9 8 Recent Trends in Post Harvest Technology and Management purpurea (Darvas, 1982) and sooty blotch caused by an Akaropeltopsis sp, are important pre-harvest diseases. The major post-harvest diseases are stem-end rot, caused by any of 10 organisms, with Thyronectria pseudotricha the most important (Darvas, 1978); anthracnose caused by Colletotrichum gloeosporioides (Kotzé, 1985) and the Dothiorella/ Colletotrichum rot complex (Darvas, 1978). In all the above instances, infection of fruit takes place in the orchard prior to harvest.sooty blotch is a field disease that is generally adequately controlled by the copper fungicide spray program used for anthracnose control. Although symptoms of thedisease are only superficial, they can reduce the market value of fruits. Recently, the causal agent of this disease in Australia was shown to be Stomiopeltis sp. (Pegg, 2001). Melon Post-Harvest During storage and transportation of melon fruits, post-harvest diseases occur, primarily caused by A. alternata, Fusarium semitectum, Rhizopus stolonifer, and Trichothecium roseum (Yang et al., 2006; Bi et al., 2007). Currently, application of synthetic fungicides is the primary means of controlling these post-harvest diseases (Ma et al., 2004). However, use of these fungicides has been progressively restricted, due to increasing concerns on the protection of the environment and human health, together with increased pathogen resistance to fungicides (Dianz et al., 2002; Marín et al., 2003; Rial-Otero et al., 2005). DISCUSSION Biological control of post-harvest disease (BCPD) has emerged as an effective non-chemical alternative. Bacillus species, including B. subtilis, produce spores that are resistant to various physical and chemical treatments, such as desiccation, heat, UV irradiation, and organic solvents (Leelasuphakul et al., 2008), and serve as excellent biological control agents against a wide range of plant pathogens by their production of antibiotics (iturin, surfactin, and fengycin), cell wall-degrading enzymes (chitinase and b-1,3 glucanase), and antifungal volatiles (Fiddaman and Rossall, 1993; Knox et al., 2000; Shoda, 2000; Jiang et al., 2001; Pinchuk et al., 2002; Kim and Chung, 2004; Leelasuphakul et al., 2006). At the same time, B. subtilis can occupy the same niche as many pathogens and play an antagonistic role (Bacon et al., 2001). Thus, B. subtilis has been recommended as a generally safe ('GRAS') microorganism by the United States Food and Drug Administration (Denner and Gillanders, 1996), which promotes its use in the food industry (Wang et al., 2010).The

10 Post Harvest Management of the Pests and Some Important... development of new fungicides based on natural compounds should include detailed investigations on their degradation in foods or in biological systems, although their natural origin makes them relatively biodegradable and with negligible residues. CONCLUSIONS Over the last two decades the increasing interest towards control measures alternative to synthetic fungicides against post-harvest pathogens has produced numerous studies with encouraging results. On the other hand, almost all the measures described above, taken individually, are unable to obtain an economically acceptable control level. So,some studies are in progress to improve their effectiveness. In the case of biocontrol agents, the formulation is still a key issue, together with the compatibility with the normal practice of fruit processing and storage. Moreover, research has highlighted some critical points that can be summarized as follows: i) difficulty in the registration of biofungicides; ii) potential toxicity to humans and the environment of so-called natural molecules and their possible phytotoxicity when used at high concentrations; iii) need for exhaustive study on the environmental fate and dispersal of the antagonist. REFERENCES Bacon, W. C., Yates, E. I., Hinton, M. D. and Meredith, F.; Biological Control of Fusarium moniliforme in Maize. Environmental Health Perspectives,109: , (2001). Bi, Y., Ge, Y. H., Wang, C. L. and Li, X. W.; Melon production in China. Acta Horticulturae, 731: , (2007). Brecht, J. K. and Yahia, E. M.; Postharvest physiology. In: Litz, R.E. (ed.) The Mango: Botany, Production and Uses. 2 nd edition. CABI. (In press). citrus fruits. Agricultural Engineering International, 5: 1-10, (2009). Coates, L. and Johnson, G.; Postharvest diseases of fruit and vegetables. In ' Plant Pathogens and Plant. Diseases', pp, , (1997). Coates, L., Willingham, S., Pegg, K., Cooke, T., Dean, J. and Langdon, P.; Field and postharvest management of avocado fruit diseases, Queensland Horticulture Institute, Department of Primary Industries, (2001). Darvas, J. M. and Kotzé, J. M.; Avocado fruit diseases and their control in South Africa. S. Afr. Avocado Growers' Assoc. Yearb, 10: , (1987). 9

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