*Phytophthora* Threats on Economic Plants in Egypt and Ghana

#### **Chapter 1**

## *Phytophthora* spp.: Economic Plant Threats in Egypt

*Waleed Mohamed Hussain Abdulkhair*

#### **Abstract**

The potato crop is exposed to infection with many fungal diseases including late blight, caused by *Phytophthora infestans*. The control of late blight disease requires an integrated management approach represented in cultivation control, plant resistance, and fungicide control. The citrus plants are infected by *Phytophthora nicotianae* that is causing root rot disease in Egypt. Three species of *Phytophthora* responsible for infection of citrus plants; *P. nicotianae*, *P. citrophthora*, and *P. palmivora*. Other pathogens associate *P. nicotianae* and form complexes or coinfection that release different diseases for citrus plants such as gummosis, *Phytophthora*–*Diaprepes* complex (PDC), and Huanglongbing syndrome (HLBS).

**Keywords:** oomycetes, pathogenicity, coinfection, citrus plants, potatoes

#### **1. Introduction**

Plants are exposed to various biotic and abiotic stresses that affect their growth and yield. Biotic stress is represented by different microbial diseases that infect the plant. Therefore, the control of biotic stress is very urgent to maintain healthy crops Egypt suffers from accelerated population growth, which hinders economic development and constitutes an explicit threat to food security if it is not decisively controlled. FAO reported that "In the next decades, Africa will suffer from severe decrease of crops due to water deficiency, adverse weather events, pests and other factors, which lead to famines and drought".

Crops are exposed to microbial infections particularly fungal infections including *Phytophthora* infection as one of the main destructive phytopathogens. Among these crops, citrus is exposed to damage and subsequently high economic loss due to *Phytophthora* infection. − spp. infect different parts of citrus plants causing various diseases such as damping-off of seedlings, fibrous root rot, crown rot, and gummosis [1]. Ten species of genus *Phytophthora* are known to infect citrus plants around the world causing serious diseases such as gummosis, and root and fruit rots [2]. Chemical fungicides are one of the control measures, which provide an effective result, but their effects are not eco-friendly due to their harmful effects. Different fungicides, including Fosetyl-Al and Metalaxyl-M, may be used separately or by alternation to reduce the development of fungicide resistance [3]. Metalaxyl-M is usually used in East African countries to control the *Phytophthora* infection prevalence in potatoes [4, 5]. Climatic conditions play an important role in the prevalence of *Phytophthora* infection in citrus plants; i.e., the root infections caused by *P. citrophthora* are severe during spring and very mild during winter, on

the other hand, the root infections caused by *P. nicotianae* are severe during summer and early autumn and very mild during winter [6].

Potato is one of the economic crops which are important for Egyptian exportation. This strategic and economic crop is exposed to complete damage by late blight disease caused by *P. infestans*, which is considered the most common disease for both potatoes and tomatoes worldwide [7–10]. Control of *Phytophthora* infection depends mainly on the contentious elimination of spoiled piles of potatoes and using a convenient means for both harvesting and storage [11]. Although different fungicides are used in the control of late blight, the phenyl amide fungicides such as Ridomil still the most effective ones [12, 13]. Nevertheless, the use of Ridomil leads to resistance development with frequent usage, so the strategy of Ridomil practice should be modified; i.e., the potatoes should be treated with Ridomil (0.75 kg ha−1) followed by another dose (1.5 kg ha−1) to prevent both formations of late blight disease and resistance development [14–16]. In such a way, using fungicides as an effective treatment for late blight disease increases the productivity of potatoes by as much as 60% and therefore decreases the economic loss [17]. In this chapter, we will elucidate the harmful effects of *Phytophthora* spp. on crops in Egypt, and the followed recent methods to control its diseases to maintain sustainable agriculture and a strong economy, therefore.

#### **2.** *Phytophthora*

The phytopathogenic fungus *Phytophthora* spp. is unrelated to true fungi and belongs to oomycetes. This oomycete has mycelia which released branched sporangiophores, which produce lemon-shaped sporangia at their tips. This oomycete is characteristic of swellings produced by sporangiophores at the places of sporangia formation [18, 19]. Different species are belonging to the genus *Phytophthora* including *Phytophthora infestans* which have two mating types (A1 and A2) which are required to produce sexual spores known as oospores. *P. infestans* is the causative pathogen of potato late blight disease [18–20]. Oospores are the main reason for new strains' release of *P. infestans* worldwide, which are more deleterious than the old strains. Sexual reproduction begins with the growth of the two mating types adjacently, where the globose oogonium is developed above the antheridium due to the growth of female hypha through the young antheridium, which in turn fertilizes the oogonium to develop a thick-walled and hardy oospore. The germination of oospores is carried out by a germ tube that produces sporangia, which germinate entirely by releasing three to eight zoospores at temperatures up to 12 or 15°C, whereas above 15°C sporangia may germinate directly by producing a germ tube [19].

#### **3.** *Phytophthora* **diseases in Egypt**

Egypt is an agronomic country that depends on the exportation of crops to develop its economy. Therefore, all agronomic pests including *Phytophthora* spp. which destroy the crops and other plants are threats and lead to decline of the economy. Potatoes and citrus plants are occupied the first ranks of Egyptian agronomic crops which export to different countries over the world, especially the European Union and Arabic Gulf countries. In Egypt, potatoes and citrus plants are usually attacked by *P. infestans* and *P. nicotianae*, respectively. These phytopathogenic fungi are very deleterious due to their severe effects and resistance ability for many fungicides. So, the control of these pathogens is a very urgent approach to maintain

healthy crops, food security, and a strong economy. In the last 5 years, the Egyptian government has succeeded to render the orange crop is the first exported citrus plant worldwide due to new strategies and sustainable agriculture programmes which are applied intensively.

#### **4.** *P. infestans*

#### **4.1 Life cycle**

Temperature plays an important role in its life cycle, where sporangia of *P. infestans* can germinate by a single germ tube at 13–21°C, and the emergence of late blight is accompanied by a moderate temperature (10–16°C) and high relative humidity [21, 22]. The fungal growth is inhibited at 30°C or more, and it can further sporulate when the temperature be relatively moderate with high relative humidity near 100% [19]. The emergence of lesions is the main symptom of late blight disease. These lesions have appeared as small circular or irregular with light to dark green color, and they are also water-soaked [22]. These lesions are appeared on both lower and upper leaves, where unfavorable and favorable climate conditions are present, respectively [22]. At high humidity, the lesions are fast enlarged with the formation of brown areas with the absence of clear borders. At these borders, a white zone (3–5 mm) of downy mildew growth has appeared on the lower sides of the leaves, and then all leaves are infected and die [19]. Therefore, there is a relationship between late blight infection and humidity, where the infection and symptoms appearance are accompanied by high relative humidity for a minimum of 7–10 hours. The late blight infection is distributed via spores scattering by wind and rain until reach healthy plants where the disease cycle begins again. The life cycle of *P. infestans* depends on two main environmental factors; humidity and temperature. The moderate temperature and high relative humidity intensively allow to formation and distribution of late blight infection. Many life cycles maybe happen in one season, and subsequently, the oomycetal infection is more prevalent even in the soil as a carrier for spores. The late blight disease can completely damage the potatoes within a few days or a few weeks when favorable environmental conditions are provided. On the other hand, late blight disease is attenuated and disappeared with dry weather, where the oomycetal activity is stopped and the existing lesions do not enlarge and turn black, curl, and wither [19].

The late blight infection begins with close contact with sporangia and tubers. Usually, late blight infection happens when sporangia are penetrating the tubers of potatoes. Developing and mature tubers are a target for sporangia; however, mature ones are a more favorable targets because they can cause cracks in the soil and give sporangia ready access. The moist soil accelerates the infection of tubers, which are usually appeared as irregular dark purple or brownish blotches. When the infected tuber is torn off, water-soaked, dark, reddish-brown infected tissues have appeared, and the oomycetal infection may be deeply extended into 5–15 mm in the tuber flesh. The coinfection may happen for the infected tubers, where other fungal and bacterial infections are present. The coinfection causes soft rots which characterize by a putrid taste and offensive odor [19, 22].

There are two types of sporangia germination of *P. infestans*; direct germination by a germ tube or indirect germination by zoospores formation. Secondary sporangia may be produced by germ tubes, and germinate at 7–13°C with the presence of free water on leaves, and form 8–12 motile zoospores per sporangium, which swim in the water and attach to the leaf surface and infect the plant. Zoospores liberate the germ tubes and by which infect the leaves either through

stomata or by direct penetration, where the mycelia grow and release long-curled haustoria between the cells. The second phase of the life cycle starts in the moist soil bearing sporangia. Zoospores profusely germinate and penetrate the tubers through the wounds [21, 22].

#### **4.2 Control**

The control of late blight infection depends on different management approaches including cultivation control, plant resistance and fungicides control.

#### *4.2.1 Cultivation control*

Control of late blight disease can be achieved by using good agricultural practices as the most common control technique including using healthy seeds, elimination of all infected potatoes, avoidance of frequent or night-time overhead irrigation, using more conventional methods for both harvesting and storage, and using more effective fungicides and herbicides to destroy the dropped infected parts of potato plant [23]. As mentioned above, the prevalence of late blight disease depends on providing adequate weather conditions (moderate temperature and high relative humidity) despite these conditions being beyond the control. Nevertheless, some measures should be applied such as the selection of proper fields and taking into account the appropriate method, time and amount of irrigation. The proper field should have good water seepage, high drainage, free from inoculum sources (infected potatoes), and also free from the weeds which restrict the air movement within the canopy and block the access of fungicides to the leaves and tubers of potatoes, and alternative late blight hosts like hairy nightshade that supports the disease prevalence [21, 22]. Sprinkler irrigation is a more adequate method for potato cultivation because it does not provide sufficient humidity that allows fungal growth and late blight disease incidence. It is preferable to grow potatoes in rows parallel with the winds to improve the air circulation and therefore foliage dryness. Conscious cultivation of potatoes requires rooting of the vines before 2 weeks of harvest, and then spraying the foliage with fungicides to kill living late blight spores. The healthy tubers should be dried during and after storage, while the infected tubers should be separated from the healthy ones [24].

#### *4.2.2 Plant resistance*

The plant resistance to late blight disease is another means for control that saves us from using fungicides and subsequently prevents or diminishes fungicide resistance. The plant resistance for late blight disease is an eco-friendly means, so the modern approach of potato cultivation depends on using resistant cultivars, which vary among each other in the resistance rate to late blight disease. Therefore, the pursuit of late blight resistance is a very urgent matter, so a lot of potato cultivars are genetically engineered to be resistant. Nevertheless, these genetically engineered cultivars can be destroyed by other new strains of *P. infestans* because the resistance is encoded by a single gene. So, using of polygenic (durable) resistant cultivars is very helpful to allow the production of healthy potatoes free from any deposits of fungicides. Although plant resistance technique is very effective for control of late blight disease, avoidance of cultivation inadequate weather for late blight emergence is required; as well as, frequent spray with an effective fungicide to completely prevent the growth of *P. infestans* [25].

#### *4.2.3 Fungicides control*

Despite the two previous effective methods in controlling the spread of late blight that infects potato plants, using fungicides are very essential to completely prevent or eradicate the late blight disease. The fungicides are also used as prophylactic agents, where they are sprayed on healthy potatoes to prevent any growth chance of *P. infestans*. The use of fungicides must be frequent and periodically because they may be broken down by weather factors. There are two types of fungicides according to their mobility named protectant and penetrant. The protectant fungicides are usually used before the incidence of late blight infection because the already infected potatoes never get rid of the symptoms of late blight and the damaged tissues are never repaired. The penetrant fungicides are effectively used after the incidence of late blight infection because they can kill the fungus and stop the prevalence of late blight infection. Both protectant and penetrant fungicides have broad-spectrum and systemic action, so they are powerful chemical control agents [26].

#### **5.** *P. nicotianae*

#### **5.1 Description**

The main pathogen of citrus plants in Egypt is *P. nicotianae* or also called *P. parasitica*. This phytopathogenic oomycete was firstly isolated from tobacco in Indonesia in 1896s. The oospores are produced from both antheridia and septate oogonia. The spherical, ovoidal, or ellipsoidal sporangia are present with one to three sharp papillae. The intercalary or terminal spherical chlamydospores and arachnoid mycelia are also present. Although *P. nicotianae* can infect around 90 different plant families, the citrus plants are still the main target of it. So, this pathogen causes a high loss of citrus plants to reach to 15% in Egypt and subsequently negatively affects the Egyptian exports from citrus plants and in turn leads to significant economic loss. The isolation of *P. nicotianae* from the soil can be carried out by different methods, but the baiting method is the most common and effective one. *P. nicotianae* can be identified either by classical methods depending on morphology determination or by genetical methods depending on SSCP fingerprinting and ITS sequencing. The eradication of *P. nicotianae* depends on the same methods mentioned above especially using effective fungicides such as Metalaxyl-M and phosphonate.

#### **5.2 Pathogenicity spectrum**

The genus *Phytophthora* has a wide array of species that reaches 120 due to the improvement of identification tools and methods, a wide survey of natural habitats, and reports of new diseases [27, 28]. This blossoming may increase in the next years where it has been reached 600 species [29]. Therefore, the host plants of *Phytophthora* genus are also extending to be about 4400 hosts [30]. The pathogenicity spectrum is differed from one species to another and subsequently influence on agronomic productivity. *P. nicotianae* is characterized by its wide pathogenicity spectrum against 90 families of plants particularly citrus ones and causes a high loss of productivity. *P. nicotianae* is widely distributed worldwide especially in temperate countries like Egypt and infects a considerable number of plants causing huge economic loss [31, 32]. This pathogen causes many plant diseases including brown rot, foot rot, root rot, gummosis, and black shank of tobacco [33].

#### **5.3 Pathogenicity behavior**

The phytopathogenic *P. nicotianae* usually infects the roots of different plants and other parts such as leaves, stems, and fruits and causes crown rot disease. The pathogenicity behavior of *P. nicotianae* is hemibiotrophic; i.e., the pathogenicity is accomplished through two steps; the first one is called biotrophy that implies the pathogen intimately contacts with the healthy tissues at the early stages of infection, and the second step is called necrotrophy in which the pathogen penetrates the tissues and profusely grows and causing tissue wilting and death. *P. nicotianae* has sporangiophores that bear multinucleate sporangia, which directly germinate in the proper weather and produce wall-less zoospores which are uninucleate and possess two flagella to can migrate until contact with the host tissues. Once contact is done, zoospores form a cell wall and cysts, which in turn germinate to form germ tubes by which they can penetrate the plant tissues [34, 35]. Moreover, *P. nicotianae* can reproduce sexually by formation thick-walled oospores as a net result of male and female gametangia fusion. Sexual reproduction leads to high genetic variation which in turn leads to releasing of novel pathogenicity and virulence factors. The main habitat of oospores is the soil where they can persist for several years until germination and formation of germ tube that penetrates the host tissues and causes the diseases.

Under hard extreme environmental conditions, *P. nicotianae* produces thickwalled asexual structures called chlamydospores, which persist in the soil very long time reach to several years. Chlamydospores can actively germinate at moderate and high temperatures, while they are dormant in low temperatures as the same with oospores. Therefore, *P. nicotianae* can tolerate the hard weather of the winter by both oospores and chlamydospores which be dormant in rhizospheres of host plants. Some animals like termites and snails are good vectors for both oospores and chlamydospores, which survive in their gastrointestinal tracts and feces [36]. It is argued that, *P. nicotianae* can reproduce sexually and asexually according to weather conditions; i.e., under proper conditions, they usually reproduce by sexual propagules, but under unfavorable conditions, they tend to asexual reproduction to tolerate the hard conditions. So, the life cycle of *P. nicotianae* includes both sexual and asexual propagules [37].

#### **5.4 Coinfection**

The coinfection implies the association of *P. nicotianae* as a soil-borne pathogen with other pathogens which together infect the host-plant tissues and cause unprecedented diseases such as the new citrus diseases, which are somewhat incurable diseases.

#### *5.4.1* Phytophthora *gummosis*

Citrus plants represent a high economic value in Egypt, so they must be protected from all destructive pathogens especially *P. nicotianae*. Citrus plants may usually be infected by 10 species of *Phytophthora*, the severe diseases are incident by only three species namely *P. nicotianae*, *P. citrophthora* and *Promecotheca palmivora*, but *P. nicotianae* is the most destructive one not only in Egypt but all over the world where it causes root rot, foot rot, and gummosis [38]. The coinfection is usually accompanied by the life cycle of *P. nicotianae*, where it is associated with *P. palmivora* in warm countries like Florida or Southern Asia, and it is associated with *P. citrophthora* in the Mediterranean countries and causing branched cankers [39, 40]. *P. citrophthora* is active in spring, while *P. nicotianae* is

#### Phytophthora *spp.: Economic Plant Threats in Egypt DOI: http://dx.doi.org/10.5772/intechopen.101115*

active in the summer and early autumn causing root infection. Therefore, *P. nicotianae* requires a high temperature more than *P. citrophthora* for growth and activity. *P. nicotianae* is a dominant phytopathogenic fungus in Brazil, Egypt, South Africa, and Tunisia. Fungicides, resistant plants, and sanitary practices are good measures for the control of *P. nicotianae* [41].

#### *5.4.2* Phytophthora*:* Diaprepes *complex (PDC)*

*Diaprepes* is the polyphagous root weevil found in citrus areas due to the distribution of infected nursery stock. The roots of citrus plants are being infected by the larvae of the weevil which are feeding on root tissues until be dilapidated and then be died. On the other hand, the infection with *Diaprepes* is followed by the infection with *P. nicotianae* through the injured roots predisposed to *Phytophthora* infections, and PDC is formed, which is an incurable disease that is very difficult to control [42].

#### *5.4.3 Huanglongbing syndrome (HLBS)*

There is another coinfection include *P. nicotianae* called HLBS that is more incurable than PDC. The name of this disease returns to the citrus greening or yellow dragon disease which is the oldest citrus disease worldwide. Although, this disease is widely distributed in most citrus areas over the world, the Mediterranean Basin region, Australia and Japan are less affected [43]. HLBS is usually transmitted by both psyllid vectors and grafting. Three varieties are belonging to unculturable Gram-negative bacterium; *Candidatus liberibacter*. The first variety was isolated from Africa; *C. liberibacter africanus* and designated as (CaLaf), the second variety was isolated from Asia; *C. liberibacter asiaticus* and designated as (CaLas), and the third and last variety was isolated from America; *C. liberibacter americanus* and designated as (CaLam) [44]. The effect of this disease is very severe because it causes vascular decline, reduces both fruit size and quality, and completely kills the trees [45]. The seriousness of this disease returns to no resistant plants are found and also no efficient management program is currently available, so the plant losses may reach 100% locally [46]. Moreover, the pathogenic bacteria attack all parts of the host plant and cause complete damage particularly if the coinfection included *P. nicotianae* is incident. Accordingly, the control of this disease mainly depends on the eradication of psyllid vectors and following the sanitary practices including removal of infected trees, which may be avoided by following a good nutrition program. Furthermore, effective mefenoxam-based fungicides can be used as helpful agents to get a ride of this dreaded plant disease. This control strategy has two disadvantages: high cost and inefficiency with mild or long persistence [3, 47].

#### **6. Methodology**

#### **6.1 Isolation of pure cultures of** *Phytophthora* **spp.**

Isolation of *Phytophthora* spp. is usually carried out by using Rye B Agar medium [48] (60 g rye grain, 20 g glucose/sucrose, 15 g agar, and 1.0 L distilled water, pH 6.8 ± 0.2). The rye grains were soaked in distilled water and left at room temperature for 36 hours. The supernatant was poured off and kept in a separate vessel, while the distilled water was added to the settled grains and heated in a water bath at 50°C for 3.0 hours. The mixture was filtered through a sieve and the grains were discarded. The filtrate was mixed with the kept supernatant, glucose/sucrose, and agar, and the

distilled water was added until the volume reached 1.0 L, and then agitated thoroughly. The mixture was autoclaved at 121°C for 20 minutes. The autoclaved medium was left to be cooled at 45°C, and 3 ml of a stock rifamycin (30 µg/ml) and 1 ml of stock piramycin (10 µg/ml) were added and mixed thoroughly.

The infected part of plant with *Phytophthora* spp. was cut into small fragments, which were placed into the healthy part susceptible to infection. The two parts were fastened back together with a rubber band and incubated at 16°C for 4–9 days. The infected part was cut into small fragments by a sterile scalpel. These fragments were disinfected in 70% ethanol for 15–20 seconds and then de-aerate in 0.1% sublimate of HgCl2 for 30–45 seconds, or in 1% sodium hypochlorite for 180 seconds. The disinfected fragments were rinsed three times with sterile distilled water, and placed onto the agar surface of Rye B medium containing antibiotics and maintained in dark at 16°C for 10 days. The colonies of *Phytophthora* were examined microscopically by a lens (400×). The sporangia of *Phytophthora* appeared in different shapes according to the species [49].

#### **6.2 Storage of** *Phytophthora* **spp.**

#### *6.2.1 Using agar slopes under paraffin oil or water*

The pure culture of *Phytophthora* spp. was grown on Rye B Agar medium for 2 weeks. The agar surface loaded by the growth of *Phytophthora* spp. was flooded with sterile paraffin oil or water and stored at 4–7°C. The sub-culture must carry out at least once every 3 years.

#### *6.2.2 Using liquid nitrogen*

The pure culture of *Phytophthora* spp. was grown on Rye B Agar medium for 10–14 days at 16°C. The growth was cut into discs by a sterile cork-borer, and placed in 1.5 ml cryovials containing a sterile 15% dimethyl sulfoxide solution (DMSO), and mixed thoroughly until be immersed. The temperature of cryovials containing *Phytophthora* discs was decreased gradually (−1°C/min) for at least 4 hours at −70°C using a specified device for this purpose. The frozen growth was transferred into liquid nitrogen (−196°C). Due to the toxic effect of DMSO on the growth of *Phytophthora* spp., the growth discs must be quickly thawed and rinsed carefully and thoroughly with sterile distilled water when out of the liquid nitrogen.

#### **6.3 Preparation of** *Phytophthora* **inoculum**

The mycelial growth of *Phytophthora* spp. was placed on the agar surface of Rye B Agar medium between two slices (1 cm) of susceptible host plant for infection. The two slices never completely cut off from each other to be closely attached with the moist medium to enhance the pathogen proliferation. The agar plates were incubated at 16°C for a week at high relative air humidity (80–100%) until thick mycelia appeared on the upper surface of the top slice. The sporangia of *Phytophthora* were collected from the mycelia by a brush and washed with deionized water. The hemocytometer was used to prepare the required inoculum concentration (50 sporangia μl −1). The inoculum was left at 7°C for 2 hours, and at room temperature for half an hour to increase the liberation of zoospores from sporangia. During the test, the inoculum should be constantly and gently agitated to prevent sporangia sedimentation and therefore zoospores accumulation that provides an adverse event on the solution surface [50].

### **7. Conclusions**

The potato is one of the economic crops in Egypt that participates in the providing of local food security and valuable national income through the exportation of agronomic crops. The production of potatoes should be provided with complete care that includes the use of modern safe methods that prevent or treat diseases that affect it, including late blight. Using of effective fungicides is one of these methods which protect from and eradicate the infection of *P. infestans*. The integrated disease management strategy is the best method to control the prevalence of late blight due to the development of new fungicides-resistant strains. The citrus plants are also economic crops in Egypt and require complete care to prevent the growth of the main destructive pathogen called *P. nicotianae* that cause different diseases especially through its association with other pathogens (coinfection).

### **Acknowledgements**

The author sincerely thanks everybody who introduced the required assistance and was helpful to complete this work.

#### **Conflict of interest**

The author declares no conflict of interest.

### **Author details**

Waleed Mohamed Hussain Abdulkhair Egyptian Drug Authority (National Organization for Drug Control and Research), Giza, Egypt

\*Address all correspondence to: waleed\_hamada@yahoo.com

© 2021 The Author(s). Licensee IntechOpen. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/ by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

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[36] Alvarez LA, Gramaje D, Abad-Campus P, GarciaJiménez J. Role of the Helix aspersa snail as a vector of *Phytophthora citrophthora* causing branch cankers on clementine trees in Spain. Plant Pathology. 2009;**58**:956- 963. DOI: 10.1111/j.1365-3059.2009. 02088.x

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[38] Cacciola SO, Magnano G. Management of citrus diseases caused by *Phytophthora* spp. In: Ciancio A, Mukerji KG, editors. Integrated Management of Diseases Caused by Fungi, Phytoplasma and Bacteria. 3rd ed. Dordrecht, The Netherlands: Springer Science; 2008. pp. 61-84

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[40] Alvarez LA, León M, Abad-Campus P, García-Jiménez J, Vicent A. Genetic variation and host specificity of *Phytophthora citrophthora* isolates causing branch cankers in Clementine trees in Spain. European Journal of Plant Pathology. 2011;**129**:103-117. DOI: 10.1007/ s10658-010-9696-8

[41] Vernière C, Cohen S, Raffanel B, Dubois A, Venard P, Panabières F. Variability in pathogenicity among *Phytophthora* spp. pathogenic to citrus in corsica. Journal of Phytopathology. 2004;**152**:476-483. DOI: 10.1111/j. 1439-0434.2004.00878.x

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[46] Graham JH, Feichtenberger E. Citrus Phytophthora diseases: Management challenges and successes. Journal of Citrus Pathology. 2015;**2**:1-11. DOI: 10.5070/C421027203

[47] Duncan LW, Rogers ME, Futch SH, Graham JH. 2014 Production guide: Citrus root weevils [thesis]. UF/IFAS Extension, Florida Citrus Production Guide, University of Florida; 2014

[48] Caten CE, Jinks JL. Spontaneous variability of single isolates of *Phytophthora infestans*. I. Cultural variation. Canadian Journal of Botany. 1968;**46**:329-348. DOI: 10.1139/b68-055

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[50] Andrivon D, Avendano-Corcoles J, Cameron AM, Carnegie SF, Cooke LR, Corbiere R, et al. Stability and variability of virulence of *Phytophthora infestans* assessed in a ring test across European laboratories. Plant Pathology. 2001;**60**:556-565. DOI: 10.1111/j. 1365-3059.2010.02392.x

#### **Chapter 2**

## *Phytophthora* Diseases in Ghana: Threats, Management Options and Prospects

*Joseph Adomako, Stephen Larbi-Koranteng, Frederick Kankam, Yaw Danso, Jerry Fenteng Asamoah, Patricia Oteng-Darko, Kennedy Agyeman, Stephen Yeboah, Erasmus Narteh Tetteh and Eric Owusu Danquah*

#### **Abstract**

Ghana's agricultural economy is largely dominated by the crop subsector with much focus on the production of tree, arable and vegetable crops. Nevertheless, *Phytophthora* spp. are major threat to the production of these crops contributing significantly to yield reduction. In this review, the main focus will be to look at the threats the pathogen poses to production, economic importance of *Phytophthora* diseases, highlights some *Phytophthora* diseases with limited research in the country but have the potential of affecting crop production, management options and the prospect of developing and deploying biological control strategies considered environmentally friendlier and devoid of human health risks to reduce the effect of this pathogen on crop production as well as reducing the dependency on chemical control option.

**Keywords:** Biocontrol, Chemical control, Epidemiology, *Phytophthora*, Symptoms

#### **1. Introduction**

Plant diseases are of significant importance in plant production globally. From the resource poor small-scale farmer to the most sophisticated commercial grower, plant diseases remain a major source of concern affecting all levels of the farming enterprise contributing significantly towards achieving a reliable world's food systems. It influences decision making process of not only producers but traders, processors and even consumers contributing immensely towards the various components of food systems. Directly, diseases impact negatively on yield and it is estimated that about 16% of global arable food is lost to diseases [1, 2]. Several pathogens cause plant diseases, however, since the infamous Irish potato famine in 1840, the pathogen, *Phytophthora* sp., has been considered the most destructive plant pathogen [3] with more than 80 species in the genus with multiple or diverse host ranges [4, 5]. Several documents have reported on the negative impact of *Phytophthora* diseases on global economy in relation to human suffering, hunger, disease and subsequent death [6, 7]. Yield losses associated with the pathogen is estimated in billions of dollars annually [8, 9].

For years, *Phytophthora* diseases have impacted tremendously on Ghana's agriculture threatening the economic livelihood of farmers most especially those in cocoa production sector. *Phytophthora* pod rot disease commonly known as the Black pod disease (**Figure 1**) caused by *Phytophthora palmivora* and *P. megakarya* is the most destructive cocoa disease worldwide accounting for over 30% pod yield loss through pod rot and 10% tree death [11]. Since the incidence of *Phytophthora* diseases of cocoa were reported in Ghana [12], high yield loss ranging between 60 and 100% has been recorded [12] with the country losing more than a quarter of its 2012 annual output of 850,000MT to *Phytophthora* spp. disease [13]. Continuous destruction of cocoa by *Phytophthora* has compelled most farmers to abandon cocoa production for other crops [14, 15].

Although *Phytophthora* diseases on cocoa have received a lot of attention and well documented in Ghana, reports on their impact on other crops are scanty and highly unavailable except for taro [*Colocasiae esculenta*] which recently has been documented. Since the initial report of taro leaf blight [16] in the Eastern region of Ghana, several researchers [17, 18] have reported the prevalence of *Phytophthora* leaf blight of taro (**Figure 2**) and morphological and genetic variations in isolates of the pathogen from different parts of the country [19]. Apart from reduction in yield, the pathogen is reported to have caused most farmers to shift from taro production to other crops such as sugar cane and rice [17]. Akrofi et al. [20] reported that plants such as *Xanthosoma saggitifolium*, *Musa paradisiaca*, *Carica papaya*, *Ananas comosus*, *Elaeis guinnensis*, *Persia americana* and *Mangifera indica* commonly used as shade plants in cocoa production, served as alternative hosts to *Phytophthora*. This is worrying as little research has so far been geared towards studying the impact of *Phytophthora* on several crops in Ghana. This clearly poses a threat to crop production especially as several reports reveal susceptibility of most of the country's food and cash crops to different *Phytophthora* species leading to massive decline in their production. For example, diseases such as the tomato late blight, pineapple heart rot, and root rot of papaya which are caused by *Phytophthora* species can greatly cause fruit and vegetable insecurity in the event of future outbreak when knowledge on them is low. These challenges and gaps present opportunities for research into *Phytophthora* diseases in the country such as assessing population structure and determining the epidemiology of *Phytophthora* diseases, identifying host ranges and designing management strategies to minimize its impact. Impact studies of the pathogen can also be carried out to quantify their effect on crop production. The aim of this review is not to exhaust all aspects on *Phytophthora* diseases in Ghana but bring to light current and potential threats on some important crops, control options being used by farmers and the need to research and promote the use of biocontrol agents in Ghana. It is believed this review will inspire Plant Pathologists to delve deep into *Phytophthora* research in Ghana.

**Figure 1.** *Pods showing symptoms of black pod diseases [10].*

**Figure 2.** *Symptoms of taro leaf blight [17].*

#### **2.** *Phytophthora* **diseases of economic importance**

Characteristics of all host plant impairments, *Phytophthora* diseases generally interrupt with the normal physiological functions of their host thereby reducing productivity and consequently lead to food and economic insecurity among populations which depend on it. Globally, impact of the late blight disease of potato, caused by the *P. infestans* [Mont.] de Bary showed clearly the significance of plant diseases and more especially those caused by *Phytophthora* species. This epidemic led to mass starvation, death and migration of people from Ireland to the United States [21]. In Ghana, the impact of *Phytophthora* diseases is highly prominent and its impact heavily felt in cocoa production. The crop is a major earner for the country accounting for about 67% of household income for about 25–30% of Ghanaians living across the cocoa growing regions [22]. As important as the economic value of cocoa to the country, *Phytophthora palmivora* and *P*. *megakarya* infections has been reported to cause a stagnating effect on its production. The disease which was first reported in Ghana in 1985 [12], covering an estimated area of about 16, 000 hectares of cocoa farm land is now prevalent across all cocoa growing areas in the country [10]. The black pod disease, caused by *Phytophthora* sp. has been described as the single most destructive limitation to the economic production of cocoa. Apart from the heavy pod loss, *Phytophthora* spp. causes stem canker in cocoa leading to the death of plant [23]. This clearly shows a reduction in plant population and consequently yield of the farm. Omane et al. [16] identified *Phytopthora colocasiae* as causing taro leaf blight disease in the country apart from *Phytophthora palmivora* and *P*. *megakarya* on cocoa. The disease has been associated with about 90 and 50% leaf and corm yield losses respectively. High incidence and severity of the disease was reported in eleven districts of the semi-deciduous agro ecologies of Ghana [17]. It causes corm rot and invasion of the rot by other pathogens such as *Lasiodiplodia theobromae* causing the corms to blacken in storage [24]. The major characteristic feature of all countries where the disease had been reported is the forced abandonment of taro production by farmers or replanting of fields with crops like sugar cane and rice [17]. This increases food insecurity in taro growing communities as the crop is used as a substitute to major food crops during lean seasons. A survey by [25] revealed high incidence of citrus trunk rot in plantations in Ghana. Reports later showed *Phytophthora citrophthora* as major cause of the disease as it causes citrus gummosis, [26] affecting major *Citrus* species such as sweet orange [*C. sinensis*], lemon [*C. limon*], mandarin [*C. reticulata*], grapefruit [*C. paradisi*], and lime [*C. aurantifolia*] [27]. The pathogen is reported to cause tree cankers leading to death and decline of the tree crop in the field. Despite several interventions by farmers and various stakeholders to possibly eliminate the menace of this disease, it had not been successful which buttressed its economic importance in citrus production [28].

#### **3. Neglected** *Phytophthora* **diseases on crops of economic importance**

Majority of research reports on *Phytophthora* diseases, in Ghana have focused on cocoa, with limited number on taro and citrus and virtually none existing for other crops. The pathogen, however, has been reported to be a great limitation to the production of many crops produced globally. Various species of *Phytophthora* cause varying degrees of damage to fruits, legumes, orchards and vegetable crops. The pathogen is responsible for several plant diseases such as late blight, root, stem and fruit rots in several crop species from different families such as Bromeliaceae [*Ananas comosus*, Pineapple], Caricaceae [*Carica papaya-* Pawpaw], Sterculiaceae [*Cola nitida*-bitter cola and *Sterculia tragacantha*], Agavaceae [*Dracaena manni*], Arecaceae [*Elaeis guinneensis*-African oil palm], Apocynaceae [*Funtumia elastic* -West African Rubber tree], Anacardiceae [*Magnifera indica*-Mango], Musaceae [*Musa x paradisiaca*], Lauraceae [*Persia americana*-Avocado], Euphobiaceae [*Ricinodendron heudelotii*-njanysa] and *Inviigia* sp. [20], although reports on disease assessment, prevalence and economic importance have not been established in Ghana. In several countries where *Phytophthora* diseases have been assessed and reported in any crop species, pre and post-harvest losses due to even latent infections during transportation and storage has been huge. Akrofi et al. [20] reported the role of some economic crops on cocoa farms in black pod disease epidemiology. Since these economic plants serves as alternative host to *Phytopthora* species on cocoa farms, then the potential of a possible disease outbreak due to *Phytophthora* cannot be ignored. Fresh fruits and vegetable crops produced in Ghana are exported to several countries for foreign exchange. *Phytophthora* infections can therefore lead to the rejection of these produce at various quarantine checks at points of entry. Furthermore, any delay in the transport of infected fruits or other produce to their destination of use will lead to huge loss as disease development is very fast when conditions are favorable.

It is worth noting that *Phytophthora* disease does not only have impact on the produce but also on the general cost of production. With the objective to manage the severity of the infestation of the pathogens, most farmers employ several methods among which chemical method of control is most preferred due to the quick result it provides. The cost of acquiring these chemicals in the long run increases the production cost of the farmer. Chemicals used in controlling most of these diseases in most cases turn to react with the environment. This leads to the contamination of water bodies and destruction of other useful microorganisms in the ecosystem. *Phytophthora* diseases have the potential of threatening the agricultural economy of the country with the potential to cause food insecurity. Therefore, serious attention needs to be paid to the disease to limit the menace of its impact on the agriculture enterprise.

#### **4. Epidemiology and symptoms of** *Phytophthora* **diseases**

Impact of climate conditions on the incidence and severity of the *Phytophthora* spp. have been reported [29]. Ndoumbe'-Nkeng [30] postulated that high levels rainfall, higher relative humidity, and lower atmospheric temperatures are known to be the main conditions favorable for the development of Phytophhtora diseases. In agreement to this, Deberdt et al. [29] also observed a significant positive correlation between rainfall and incidence of the *P. megakarya* pod rot. It has been observed in Ghana that the occurrence of the disease is between July and October across the cocoa growing areas [15, 31]. According to [32], Phythophtora disease cycle is denoted by a parasitic phase which occurs during wet and dry seasons.

Phytophthora *Diseases in Ghana: Threats, Management Options and Prospects DOI: http://dx.doi.org/10.5772/intechopen.99135*

*Phytophthora* spp. over-seasons on pod husks, in the soil, leaf debris and or roots or shade plants [33]. When conditions are favorable [mostly during the rainy season], there is a germination of the fungi sporangia, followed by the releasing of motile zoospores of the *Phythophtora* mostly in free water and quickly spread to cause destruction of host plant. *Phytophthora megakarya* and *P. palmivora* for example undergoes series of developmental phases to form the disease cycle (**Figure 3**). Symptoms of *Phytophthora* infections can be observed on every part of an infected plant mostly under wet or humid conditions. In almost all foliar diseases resulting from *Phytophthora* infection, the appearance of small translucent spot are the initial symptoms which later appears as brown to darkened spots of lesions on the affected parts [11]. These spots coalesce as environmental conditions favors it. In cocoa for example, infected pods result in browning, blackening, shriveling up, or total rotting of the pod [20]. Infected roots cause plants to pull up easily from the soil due to root

**Figure 3.** *Disease cycle of P. megakarya on cocoa [20].*

**Figure 4.** *Stem canker of cocoa [www.pestnet.org].*

**Figure 5.**

*Symptoms of* Phytophthora *infection causing pineapple heart rot (A), Avocado fruit rot (B) and Papaya fruit rot (C). [34, 35] (https://www2.ipm.ucanr.edu/agriculture/avocado/Phytophthora-fruit-rot/).*

rot and loss. In most instances, mycelial growth covers infected plant parts areas under moist conditions. *Phytophthora* diseases can also cause cankers (**Figure 4**), fruit rots (**Figure 5**) and leaf blight (**Figure 2**).

#### **5. Management of** *Phytophthora* **diseases**

Crop disease management is one of the heaviest cost burdens in the crop production enterprise. The neglect of diseased farms without control or management interventions can cause a serious loss to the farmer. Management of plant diseases aims at either attacking the pathogen directly or creating a condition that will be unfavorable for its establishment and development. Achieving this calls for the employment of several possible control methods and strategies.

For years, various fungicides have been employed in the control of *Phytophthora* diseases most especially black pod disease in cocoa [36–39] and recently *Phytophthora* leaf blight of taro in the country [40, 41]. The chemical control relies mainly on copper-based fungicides and systemic fungicides such as metalaxyl and phosphonates. Among them are Kocides 101 [77% cupric hydroxides], Cocoabre Sandox [56% cuprious oxides], Copper Nordox 50 [50% cuprous oxide], Copper Nordox 75 [Copper oxide] Champion [77% cupric hydroxide], Ridomil 72 plus [12% metalaxyl and 60% cuprous oxide] among others for the control of *P. palmivora* and *P. megakarya*, the two main causal agents of *Phytophthora* pod rot of cocoa [42]. The effectiveness of fungicide for the control of *Phytophthora* disease, however, depends on factors such as the climatic conditions at the time and location of application, the crop variety, and pathogen species among others like social and economic considerations [38]. To be able to achieve an effective chemical control of *P. megakarya*, fungicides have to be sprayed at shorter intervals. In agreement with this, [15] reported that whiles a by-weekly application was recommended in Cameroon due to high and frequent rainfall, an average of 4-weeks intervals in Ghana was effective. This deference could be attributed to the differences in the frequency and amount of rainfall in Cameroon and Ghana. Chemical control in most cases have been reported to be costly. This makes chemical control unattractive to many peasant farmers. However, this approach could be cost effective when crop price is comparatively high and the crop is also under a low disease pressure [14].

Cultural control strategies according to [43], is one of the ancient strategies in the management of plant diseases. It is the strategic use of the day-to-day farm practices to either inhibit, obstruct the establishment, growth and development of the pathogen. Cultural control system has proved not only to increase yield but also created the conducive environment for efficient performance of applied fungicides [44]. To the

Phytophthora *Diseases in Ghana: Threats, Management Options and Prospects DOI: http://dx.doi.org/10.5772/intechopen.99135*

low-income farmers, cultural control is the most cost-effective disease management approach. This is because it does not require any extra cost apart from that which has already been the situation. For instance, early harvesting, removal of infected pods and pruning of infected branches reduces the inoculum load present by the primary or secondary infection. As postulated by [32], the appropriate tree spacing improves aeration, reduces huge canopy humidity and also keeps leaf mulch or litter in check. However, Luterbacher [45] in contrast of this report also reported that leaf litter has no major impact in reducing cocoa pod infection from soil inoculum. Despite the promising impact of this method, it was also observed that the sole implementation of this approach could be labour intensive and thus needed to be complemented with other control methods [30, 31, 46].

With frequent travel and trade within Ghanaian cities and regions, the fast spread of *Phytophthora megakarya* has been linked to the movement of plant materials from one district to another [15, 23]. This poses a high risk as several plant diseases are moved from infected regions to an uninfected region. Quarantine method could be adopted to overcome this menace. The quarantine system of plant disease control ensures that agriculture and natural resources in a localized area or district or region are safeguarded against the entry of disease pathogens. This will help to ensure an abundant, high-quality, and varied food supply within the territory and beyond.

#### **6. Novel approaches to control** *Phytophthora* **diseases in Ghana: success, challenges and prospects**

In the management of *Phytophthora* diseases in Ghana, especially cocoa diseases, much emphasis has been laid on chemical and cultural control as against other control options such as biological control. In the chemical control of *Phytophthora* disease, there has not been only an over reliance but an abuse of synthetic fungicides which have both health and environmental effects although the strategy is quicker, reliable and effective [47]. Utilization of control option such as biological control is not only imperative but possible, since there are numerous reported cases of biological control attempts [48–51]. Biological control strategy if harnessed will not only become a complementary but also an alternative for the control of *Phytophthora* disease as it is considered as an environmentally friendly form of disease control [52]. Biological control is the judicious use of an antagonist, its parts or product (antibiotic/secondary metabolite) to inhibit, prevent or control plant diseases. Directly, it protects their host using mechanisms such as competition for nutrients, root colonization and competition for infection sites, secretion of extracellular lytic enzymes and hyperparasitism, and induction of plant resistance. Indirectly, it promotes plant growth thereby protecting the plant from pathogen's attack [53, 54]. Not much reported success stories on the use of biocontrol agents against *Phytophthora* diseases in Ghana, but several attempts such as identifying microbial antagonists, botanicals, and resistant varieties have been initiated which needs to be appreciated.

There have been reports on the use of natural agents against *P. palmivora* and *P. megakarya* in Ghana especially *in vitro.* Not much work have been done in the field. The first of such reports was by Attafuah [55] who demonstrated that there was an inhibition of *P. palmivora* by an isolate of *Pseudomonas aeruginosa* [Schröter] Migula on cocoa husk *in vitro.* It was reported that the antagonist was isolated from cocoa mealybug, *Planococcoides njalensis* Laing and tested against *P. palmivora*. It was through the effort and the works of Attafuah that formed the basis for Odamtten and Clerk [56] to work with *Aspergillus niger* and *Trichoderma viride*. Their results showed that

metabolites of *A. niger* and *T. viride* inhibited zoospore motility, direct germination and indirect germination of sporangia, mycelial growth, sporulation and sporangial size of *P. palmivora in vitro*. Akrasi [57] isolated and identified eight *Bacillus* species strains from yam rhizosphere which were antagonistic to *P. palmivora*, the causal agent of cocoa pod rot disease (Black pod disease as being referred to in Ghana). Akrasi [57] elucidated that the filtrates of the rhizobacteria were fungitoxic and thermostable when exposed to temperature of about 121°C during autoclaving. He also reported that the filtrates of the bacteria were comparable in their effect to two fungicides, Thiophanate Methyl [Topsin M 70 WP] and Ridomil 72 plus [72% WP].

Based on the findings of Akrasi [57], [58] applied the promising rhizobacteria as protectant on cocoa pods and reported that that both broth culture and culture filtrate of the rhizobacterium isolates applied, completely inhibited *P. palmivora* infection and lesion development on detached cocoa pods. In recent studies, the rhizobacterium was identified as *Bacillus amyloliquefaciens* and field studies conducted alongside with two other antagonist viz. *Aspergillus* and *Penicillium* spp. showed these three antagonists as having potential to be developed as biocontrol agents against the black pod disease of cocoa [59].

Apart from the numerous inorganic pesticides, reports on the use of plant-based fungicides against *Phytophthora* in Ghana is limited. However, Awuah [60] postulated that natural substances from plants possess antimicrobial effects that could be potentially used in the control of *Phytophthora* diseases. This was based on the fact that, crude steam distillate of *Ocimum gratissimum* completely inhibited the growth of the pathogen and prevented black pod development on detached cocoa pods. The author further reported that the use of *Cymbopogon citratus* and *O. gratissimum* against the black pod pathogen in the field were effective against the black pod pathogen comparable to Kocide 101 [60].

For years several attempts have been made in the identification, breeding and selection of germplasm especially in cocoa for resistance to *P. palmivora* and *P. megakarya*. The use of such traditional breeding techniques for the breeding of cocoa resistance to *P. palmivora* and *P. megakarya* has been of little success. There is a welldocumented reports on screening of cocoa accessions for resistance to *P. palmivora* [61]. There was also a programme to assess the existing cocoa germplasm in Ghana for resistance or tolerance to *P. megakarya* [62]. However, [63] reported that there were no cocoa genotypes with immunity to the black pod disease pathogens in Ghana. Modern breeding approaches are currently employed to determinine the mode of inheritance, combining ability and heritability of resistance to *P. palmivora* and *P. megakarya* in cocoa germplasm [64]. Cocoa hybrids such as Alpha B36xPa7/808, Pa7/808 pound 7 and Alpha B36 xT65/326 were identified to possess different levels of resistance against major cocoa diseases [65]. With respect to taro, some germplasm have shown high level of tolerance to *P. colocasie* [19, 66].

The main challenges confronting the development and use of biological control as complementary/alternative to chemical control options in Ghana are the lack of Government initiative to promote biological control as against the importation and use of synthetic fungicides that have health and environmental effect. In some countries, there are policies to promote the use of biological control agents for the control of plant diseases. Through the National Research Initiative and other USDA programmes, research funds are made available for funding biological control activities. Among such funds are the Section 406 programme, IR-4, Regional IPM grants, and Integrated Organic Programme. Funds are also made available to stimulate the development of commercial ventures for the small business innovative research [SBIR] programmes [67]. The Government of Ghana therefore has to make it as a policy to promote research and encourage the usage of novel control options to complement the use of chemicals in an integrated manner. Scientific research in

Phytophthora *Diseases in Ghana: Threats, Management Options and Prospects DOI: http://dx.doi.org/10.5772/intechopen.99135*

Ghana on biological control needs to be coordinated leading to the establishment of Biological Control Community of Practice to encourage effective research and promotion of biocontrol agents. Farmers and other stakeholders need continuous education to raise their awareness on the dangers of abusing synthetic pesticides and its effect on health and the environment.

Notwithstanding the challenges, the future looks bright for the development of biological control and other control strategies in the country to mitigate the effects of *Phytophthora* due to the fact that awareness on the impact of the pathogen on crop production is gaining attention and research to characterized the structures and functions of biological control agents, pathogens, and host plants at molecular, cellular, organismal, and ecological levels are gradually receiving attention of plant pathologists and breeders in the country. To ensure that world food becomes safer in the next decade, then there should be increase in demand for safer pesticide in Agriculture and the solution should therefore be a biological control in an integrated management [IM] systems.

#### **7. Conclusion**

*Phytophthora* disease and its impact as a potential cause of food insecurity is something that every economy has to seriously take into consideration. It affects a wide range of crops; fruits, vegetables, legumes, root and tubers. It causes total yield loss, both in the field, transport or even in storage due to latent infection. Despite the threat posed by this pathogen, limited studies have been carried out on most crops in Ghana. In this chapter, we able to elucidate the various crops that are affected by the pathogen, the effort being made to manage it, the prospect of using biocontrol agents against the use of chemical fungicides due to their effect on the environment and humans. The review has also thrown more light on how concentration has been on *Phytophthora* pod rot disease of cocoa at the neglect of other equally important diseases caused by the pathogen. Highlighting the challenges confronting the use biocontrol as an option, the main issue addressed was lack of governmental policy to promote this practice and insufficient funding to promote research on *Phytophthora*. More attention is therefore needed with the aim of limiting its impact on food and tree crops production in Ghana.

#### **Conflict of interest**

Authors declare no competing interest.

#### **Author details**

Joseph Adomako1 \*, Stephen Larbi-Koranteng2 , Frederick Kankam3 , Yaw Danso1 , Jerry Fenteng Asamoah1 , Patricia Oteng-Darko1 , Kennedy Agyeman1 , Stephen Yeboah1 , Erasmus Narteh Tetteh1,4 and Eric Owusu Danquah1

1 CSIR-Crops Research Institute, Kumasi, Ghana

2 College of Agricultural Education, Apenten Appiah-Menka University of Skills Training and Entrepreneurial Development, Asante-Mampong, Ghana

3 Department of Crop Science, Faculty of Agriculture, Food and Consumer Sciences, University for Development Studies, Tamale, Ghana

4 Department of Agroforestry, Kwame Nkrumah University of Science and Technology, Kumasi, Ghana

\*Address all correspondence to: joeadomako@gmail.com

© 2021 The Author(s). Licensee IntechOpen. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/ by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

*DOI: http://dx.doi.org/10.5772/intechopen.99135* Phytophthora *Diseases in Ghana: Threats, Management Options and Prospects*

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## Section 2
