Preface

*Phytophthora* is a microbial genus belonging to a fungi-like group of oomycetal phytopathogens. This genus has many species that affect different parts of the plant, especially the root and stem base. The diseases of *Phytophthora* are usually accompanied by definite symptoms such as wilting and foliage discoloration. *Phytophthora* is widely prevalent worldwide because it can survive under extreme conditions and different habitats like soil and plant debris.

Microbial infection with *Phytophthora* spp., one of the more destructive phytopathogens, is a common reason for loss of economic crops. The agronomic countries depend mainly on exportation of essential plants like fruits, vegetables, and cereals. Thus, damage to these plants leads to economic loss and food security threats. Various species of *Phytophthora*, including *P. cinnamomi*, *P. cryptogea*, *P. citricola*, *P. cactorum*, and *P. cambivora*, damage different plants including ornamental horticulture plants. *Phytophthora* infects the aerial parts of the plant, targeting the root and stem base. However, some species of *Phytophthora*, such as *P. ilicis*, *P. ramorum*, and *P. kernoviae*, affect only the aerial parts of plants.such as *P. ilicis*, *P. ramorum*, and *P. kernoviae*.

Discoloration and decay are symptoms of infection of roots and stem bases. Foliar symptoms do not appear until most of the plant's roots have been killed, or microbial invasion of the stem base has been carried out. The infected foliar parts of plants like conifers are usually associated with clear symptoms such as wilting, shedding of leaves, dieback, and a gradual fading of color. *Phytophthora* infection leads to retarding of water and nutrient delivery to the stem, therefore resulting in the symptoms mentioned previously. Extreme conditions like drought will hasten their onset. As such, constant examination of roots and stem bases is essential because the foliar symptoms never appear at the early stages of *Phytophthora* infection of the roots. Some other foliar symptoms are represented as wet, dark brown to black spots on the leaves and stems causing wilting and aerial dieback but no stem or root death.

Although *Phytophthora* belongs to a fungi-like group called oomycetes, it is more closely related to algae. *Phytophthora* is a motile microorganism that migrates via tiny spores called zoospores, which quickly move in water and attract to the roots due to chemical exudates. Poor discharging or retaining of water inside the plant leads to worse disease because zoospores require water to survive and move. Other long-living spores produced by the *Phytophthora* species are called oospores and chlamydospores, which are liberated after roots decay in the soil causing contamination even for compost and standing areas. But oospores are more dangerous than chlamydospores because they can survive outside the host. Unfortunately, the fungicides used for *Phytophthora* control are fungistatic not fungicidal, so disease progression takes place after fungicide decays. Other than fungicides, there are various chemical disinfectants and non-chemical methods like steaming, solarization, and bio-fumigation used for *Phytophthora* control.

The final and radical solution to the problem of *Phytophthora* infection of plants is based on two axes. The first axis is prophylactic, that is, prevention of *Phytophthora* infestation via continuous disinfection of irrigation water sources, preventing sewage from reaching the soil, purifying the soil continuously from weeds and harmful plants, and spraying pesticides and fungicides in reduced doses. The second axis depends on the treatment in the event of any infection, whether to the roots, stems, or foliar parts of the plant, by spraying fungicides in intensive doses with re-examination of the tissues of all plant parts to ensure plant safety and to stop disease spread.

Advisements given to farmers in the form of preventive measures include draining any open soil and standing water, ensuring water irrigation is free from *Phytophthora*, covering water reservoirs to prevent contamination, filtrating and sterilizing water, using disposable tools like pots and trays or at least carefully disinfecting reused ones, and taking only healthy cuttings at propagation. Those individuals importing plants should inspect all plants and remove any that show signs of infection.

This book is divided into three sections. Section 1, "*Phytophthora* Threats on Economic Plants in Egypt and Ghana," includes Chapter 1 "*Phytophthora* spp.: Economic Plant Threats in Egypt" and Chapter 2 "*Phytophthora* Diseases in Ghana: Threats, Management Options and Prospects." Section 2, "Biocontrol of *Phytophthora* Infections," includes Chapter 3 "Plant Beneficial Microbes Controlling Late Blight Pathogen, *Phytophthora infestans*" and Chapter 4 "Endophytic Microorganisms as an Alternative for the Biocontrol of *Phytophthora* spp.". Section 3, "Prevalence and Recognition of *Phytophthora*," includes Chapter 5 "*Phytophthora* Diseases Prevalence, Its Effects and Controls in Ghana" and Chapter 6 "Recognition and Early Stage Detection of *Phytophthora* in a Crop Farm Using IoT".

> **Waleed Mohamed Hussain Abdulkhair** Microbiology Department, Egyptian Drug Authority, (National Organization for Drug Control and Research, formerly), Giza, Egypt

## Section 1
