This document discusses the early blight disease of tomatoes caused by the fungus Alternaria solani. It describes the pathogen, including its scientific classification and physical characteristics. The document outlines the disease symptoms which include brown-black leaf spots and stem lesions. It also covers the disease epidemiology, including favorable warm, wet conditions for spread. Management strategies discussed are cultural controls like crop rotation and debris removal, as well as chemical controls using fungicides applied every 15-20 days.

1. COLLEGE OF AGRICULTURAL TECHNOLOGY
(Affiliated to Tamil Nadu Agricultural University, Coimbatore-3)
Kullapuram (Po),ViaVaigai Dam, Theni-625 562
TOMATO EARLY BLIGHT
STUDENT COURSE TEACHER
T.MANOJ KUMAR Dr. PARTHASARATHY. S
2015021077 Asst. Prof., (Plant Pathology)

2. Disease Name:
Tomato Early blight
Pathogen Name:
Alternaria solani
Common Name:
Early Blight
Hosts:
Tomato, potato, egg plant and other solanum family.

3. Systematic Position
Kingdom : Fungi
Phylum : Ascomycota
Class : Dothediomycetes
Order : Pleosporales
Family : Pleosporaceae
Genus : Alternaria
Species : A. solani

4. Occurrence
History and Diversity
Early blight is caused by Alternaria solani (Ell. &
Mart.) L.R. Jones and Grout.
A. solani is problematic in tomato production areas
east of the Rocky Mountains and is generally not an
issue in the less humid Pacific or inter-mountain
regions

5. Pathogen description
The mycelium which is septate and branched, hyaline
in the beginning and later becomes darker in colour.
The conidia are 12-20 × 120-296 µm and are found
singly or in chains of two.
Conidiophores are short and produces an obclavate or
muriform shaped conidia with horizontal and vertical
septation and it is pointed at distal end.

6. Symptoms:
Foliar symptoms of A. solani generally occur
on the oldest leaves and start as small lesions
that are brown to black in color.
These leaf spots resemble concentric rings a
distinguishing characteristic of the pathogen.
Both the area around the leaf spot and the
entire leaf may become yellow or chlorotic.

7. Under favorable conditions (e.g., warm
weather with short or abundant dews),
significant defoliation of lower leaves may
occur, leading to sunscald of the fruit.
Stem lesions are dark, slightly sunken and
concentric in shape.
 Fruit spots are similar in appearance to those
on leaves – brown with dark concentric
circles. Mature lesions are typically covered
by a black, velvety mass of fungal spores

8. Leaf lesion of Alternaria solani Stem lesion of Alternaria solani
https://en.wikipedia.org/wiki/Alternaria_solani

9. https://www.ipmimages.org/browse/detail.cfm?imgnum=5393411

10. Spread of disease
Mode of survival:
The conidia and the mycelium in the soil or in
the debris of the affected plants can remain viable for
more than 17 months.
Mode of spread:
Primary spread by air borne conidia
Secondary spread by infected plant debris

11. Epidemiology:
Dry warm weather with intermittent rain.
Poor vigor.
Temperature: 25-30°C.
Poorly manured crop.

12. Management
Cultural control
Clear infected debris from field to reduce inoculum for
the next year.
Rotate to a non-Solanaceous crop for at least three
years.
Removal and destruction of infected plant debris
should be done because the spores lying in the soil are
the primary source of infection

13. Chemical control
Very early spraying with Zineb or captan 0.2% and
repeating it for every 15 – 20 days gives effective
control.