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European Journal of Applied Sciences – Vol. 13, No. 1

Publication Date: February 25, 2025

DOI:10.14738/aivp.131.18203.

Larbi-Koranteng, S. (2025). Etiology, Epidemiology and Management of Diseases: Warfare Between the Pathogen and the

Pathologist. European Journal of Applied Sciences, Vol - 13(1). 307-331.

Services for Science and Education – United Kingdom

Etiology, Epidemiology and Management of Diseases: Warfare

Between the Pathogen and the Pathologist

Stephen Larbi-Koranteng

Department of Crop and Soil Sciences, Faculty of Agriculture Education,

Akenten Appiah-Menka University of Skills Training and

Entrepreneurial Development (AAMUSTED), Mampong campus

ABSTRACT

Perhaps, pathogens are the main biotic factor that cause diseases of plants reducing

yield considerably. Man in its interest and effort tries to defend/protect these plants

from the harassment by these pathogens. This review tries to look at the pathogen

as a causal agent of diseases, disease development and the pathologist as

management strategist employing various options to bring the pathogen under

control. This initiative to unravel the causes of disease, disease development and

management is seen as a “warfare” between the pathogen and the pathologist as

each of them is seen to be smarter in its approach. Different strategies from both

ends were examined and mechanisms by which each of them uses to outwit the

other in this warfare are discussed. There is no doubt, the pathogen is far ahead and

the most intelligent. It always tries to be a step ahead and seems to be dictating the

pace with resultant nightmares/sleepless nights to the pathologist. The pathogen

also tries to set the questions for the responses from the pathologist. Nevertheless,

the pathologist has never relented in its effort to always find an antidote/solution

to the swiftly and slippery nature of the pathogen. In nature’s own wisdom, perhaps

it would be impossible for the pathologist to find a lasting antidote/solution, as this

might appear to bring plant pathology as a profession to an end. The fight for

supremacy therefore continues unabated.

Keywords: pathogen, pathologist, warfare, different strategies.

INTRODUCTION

Since creation, living things depended on each other for survival. Man, animals, plants and

microorganisms depended on each other for food and nutrition. Man, a superior living thing

with particular interest in all others tries to protect each of these living things for maximum

benefits. Particularly, man depends on plant for all the nutrients needs, be it carbohydrates,

protein, fiber, fat and oils, vitamins, minerals etc. Man, also depends on plants for economic and

social benefits. For instance, what would have been the faith of national economies like Ghana

if it does not protect its cocoa industry against the Black pod disease? With a common saying

that “Ghana is Cocoa and Cocoa is Ghana” (OPEC FUND 2022). This has led to man’s interest to

protect these plants against other competitors such as animal and microorganisms.

Microorganisms have been at the forefront in competition against human beings for maximum

benefit from the plant. One particular instance is fighting the microorganisms from deriving its

nutrient from the plants. In the quest of the microorganisms deriving its nutrient from the plant,

not only leaves the plant with pathological effects but also reduce/minimize the yield that

otherwise will have served as food for the ever-growing human population (UN report 2019).

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European Journal of Applied Sciences (EJAS) Vol. 13, Issue 1, February-2025

It is in view of this that man has always been at the war front with the pathogen doing

everything possible to free the plant from these microorganisms as pathogens from causing

“harm” to the plant. Pathogens have caused indirectly devastating effect to human race since

time in memorial, recalls can be made to the 1846 “Irish famine” that caused death of about half

a million people and at the same time the migrating of about same number to United State of

America in search of food for survival (Agrios 2005). History tells us that the pathogen has

always been a step ahead of man in this warfare. It is the pathogen in its quest for survival,

initiates the process of deriving nutrient from the plant. The pathogen finds the plant as a

suitable partner/host and therefore initiates close association with it but this association with

the help of the environment always becomes detrimental in its effect to the host plant. After

exhausting the nutrients from the plant, the plant is denied survival that leads to the decrease

in potential yield of the plant or eventually die. Man realizing its dependency of the plant under

threat from the pathogen, therefore starts devising means for a fight against the pathogen.

This warfare has lingered on for over a century with each party trying to outwit the other. The

question is therefore not about who wins this fight but the various ways the pathogen initiates

these diseases, how the diseases develop and the effort man/pathologist makes to manage the

disease to bring the effort of the pathogen under control. This review gives insight into the

nature of the fight and the strategy each try to employ to outdo the other. The review therefore

tries to look at the various mechanisms/strategies use by both the pathogen and the pathologist

and the various roles played or contributions made by pathologists to grant the plant the

maximum freedom to produce to its maximum capability, so that maximum yield can be derived

from the plant to save the ever-growing population to end hunger and malnutrition (SDG goal

2).

HISTORICAL ANTECEDENT OF PLANT DISEASES

It is a common knowledge of the negative effects of plant diseases on food security worldwide

which has been acknowledged in time past. Early evidence of plant diseases dated back in the

Old Testament of Holy book, the Bible and other early reports by Indians, Sumerians and the

Romans made references to plant diseases dated back to 2000 BC with their devastated effect

especially causing different levels of famine and other economic loses (Norrie 2016). In fact,

early documentation of plant disease at that time was basically descriptive and current concept

of diseases and pathogens were non-existence where the causes of those diseases that affected

plant appeared superstitious. Evidence of this was the festival of the Romans that was

celebrated to pacify and sacrifice of red dogs to appease the gods, because it was believed at the

time that rust disease that effected farmers cereals were as a result of dissatisfaction of the

gods. One of such festivals was Robigalia and the god was Robigus (Secoy & Smith 1978) and

appeasing this god was seen as a method of managing the disease. This era marked the

beginning of plant disease control, an important aspect of plant pathology.

Whetzel (1918) in his ‘outline of the history of plant pathology” divided the period of plant

pathology into different era; Premodern era (expanding from the 17th to the middle of the 19

century and the Modern era (from the middle of the 19th century to date). During the period of

the pre-Morden era, the description of plant diseases became more detailed, systematic and

accurate in the time of Johann Batista Zallingger (1731-1785) which became known as the

Zallingerian period and constituted the first part of the pre-modern era, then in the later portion

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Larbi-Koranteng, S. (2025). Etiology, Epidemiology and Management of Diseases: Warfare Between the Pathogen and the Pathologist. European

Journal of Applied Sciences, Vol - 13(1). 307-331.

URL: http://dx.doi.org/10.14738/aivp.131.18203

of the pre-modern era constituted the “Ungerian period”, named after Franz Unger (1800-

1870). Franz initiated the process of identifying disease pathogens and their description. The

initial perception was that these organisms were not thought to actually cause the diseases but

were thought to have been originated from the plant itself rather than from external sources.

At this era, the descriptions were not done by Plant Pathologist but rather by Plant Physiologist

since the effects on the plant were as a result of disruption of the plant physiological processes

rather than the pathogen effect and also due to non-existence of such specialists at the time.

The pathogens were thought to have originated through the process of autogenesis, origination

of life from non-living things. Despite these assumptions, pathogens were worthy of given

names and classification. This initiated the thought and rise to the Modern era with the

evolution of the Gem Theory.

Though many scientists in the Ungerian period, believed in the autogenesis, many others were

adamant of this believe. One such person was Henry-Loius DuHammel du Moncecau (1728)

who gave accurate description of a disease and the pathogen who caused the disease, he

demonstrated the pathogen's capacity to survive and propagate independently of the Saffron

crocus plant. He consequently reported the diseases to be caused by a parasitic fungus,

Helicobasidium purpureum and concluded that the disease was infectious. Another prominent

entomologist, Johan Christian Fabricius of Danish origin, published his ideas about how plants

become diseased as far back as 1774. In his publication, he opined that fungi found associated

with diseased tissues were separate living entities and did not emerge from dying tissues as

hypothesized by other proponents.

GENESIS OF PLANT PATHOLOGY AS A DISCIPLINE

Initially the study of plant pathogens and diseases they cause were an aspect of botany or part

of mycology, so plant pathology was initially called Applied Mycology. This idea persisted far

into the 20th century until in 1883, in Copenhagen, Denmark, a plant pathology was established

at the Royal Veterinary and Agriculture University to study plant diseases and their cause. By

this time, plant pathology has gained relevance in the field of crop science in various

universities across the world. One-person worth mentioning is Emil Rostrup, a professor at the

plant pathology department, Royal Veterinary and Agriculture University, Copenhagen. He was

a specialist of plant diseases at the time and mostly farmers’ consultant. Among his notably

works was a book he published in 1870 titled “Om sygdromme hos de pa marken dyrkede

planter” simply put, diseases of field crops. By 1884, he has initiated comprehensive systematic

survey of plant diseases of field crops. Many more of such pioneers in plant pathology are worth

mentioning. Even though the initial objective of plant pathology was aimed at cataloguing and

describing different plant diseases and their pathogens, attention was sooner turned towards

their control and management. Diseases control, therefore became critical objective of plant

pathology as science which continued with the study of the interaction between the host plant

and the pathogens which added more to the body of knowledge as a discipline.

THEORIES OF DISEASE DEVELOPMENT

Disease Triangle

The disease triangle is the demonstration of the pressure the pathogen exerts on the host plant

with the favor of the environment which pushes the plant to succumb to the pathogens attack.

Diseases jeopardize effective ecological restoration and agricultural yield as a basis for food