Plant Pathology, Symptomatology and Identification of diseases with reference to Fungal, Bacterial and Viral infections

Principles of Plant Pathology:-

Plant pathology:- It is the science that studies the causes of plant diseases, the mechanisms by which diseases develop in individual plants and in plant populations, and the ways and means by which plant diseases can be managed or controlled.

Fathe of Plant Pathology:- Heinrich Anton de Bary

Father of Modern Plant Pathology:- Sir Edwin John Butler

Plant Disease:- is a dynamic process where a living or nonliving entity interferes with the normal functions of a plant over a period of time.

Disease Triangle:- The disease triangle points out that three favorable conditions must coexist to cause a disease problem. These three conditions are the presence of a pathogen, a susceptible host (plant) and proper environmental conditions.

Basic plant pathology terminology:-

Parasite:- Feeds on another living organism.

Saprophyte:- Feeds entirely on dead matter.

Pathogen:- Entity capable of causing disease.

Life cycle:- Successive stages in the growth and development of a pathogen.

Vector:- Assist in spread/movement of disease agent (inoculum)

Host plant:- Plant with the ability to develop a disease caused by a particular pathogen.

Nonhost plant:- Plant that cannot be infected by a particular pathogen.

Host range:- All the plant species (cvs./var.) that can be infected by a particular pathogen.

Resistance:- Ability of a host plant to resist a pathogen, either partially or completely.

Susceptibility:- Inability of a host plant to resist a pathogen, either partially or completely.

Symptom:- Abnormal appearance of a plant.

Sign:- Physical presence of a pathogen. 

Symptomatology and Identification of diseases:-

1. Fungal disease symptoms:-

> Birds-eye spot on berries (anthracnose)

> Damping off of seedlings (phytophthora)

> Leaf spot (septoria brown spot)

> Chlorosis (yellowing of leaves)

2. Bacterial disease symptoms:-

> Leaf spot with yellow halo

> Fruit spot

> Canker

> Crown gall

> Sheperd’s crook stem ends on woody plants

3. Viral disease symptoms:-

> Mosaic leaf pattern

> Crinkled leaves

> Yellowed leaves

> Plant stunting