plant disease diagnosis

1. Presentation On:
Basic Procedures in the diagnosis
of plant diseases
Submitted To: DR. Naveed Aslam
Submitted By: Ali Raza C-010
Ammad Ahmad C-024
M Awais Sharif C-033
The Islamia University Of
Bahawalpur

2. Types of Diseases
1. Infectious diseases ( Pathogens/
Biotic factors)
2. Non-infectious diseases
( Environmental Factor/ Abiotic
factor)

3. Signs & Symptoms
Signs:
A sign of plant disease is physical evidence of the
pathogen. For example, fungal fruiting bodies are a
sign of disease. When you look at powdery mildew on a
lilac leaf, you’re actually looking at the parasitic fungal
disease organism itself.
Symptoms:
A symptom of plant disease is a visible effect of disease
on the plant. Symptoms may include a detectable
change in color, shape or function of the plant as it
responds to the pathogen.

4. Infectious Diseases
Pathogens (fungi, bacteria, parasitic higher
plants, nematodes, viruses, mollicutes, and
protozoa)
Surface of the plants (some fungi, bacteria,
parasitic higher plants, and nematodes)
Inside the diseased plant (at the margins of
the affected tissues, at the vascular tissues, at
the base of the plant, and on or in its roots)

5. Diseases Caused by Parasitic
Higher Plants
Parasitic higher plant (e.g., dodder,
mistletoe, witch weed, or broomrape)
Dodder Plant

6. Diseases Caused by Nematodes
Nematode is present on, or in the
rhizosphere of a plant showing certain kinds
of symptoms
Nematode can be identified as belonging to a
species or genus known to cause such a
disease

7. Diseases Caused by Fungi
Signs:
Leaf rust (common leaf rust in corn)
Stem rust (wheat stem rust)
Sclerotia (white mold)
Powdery mildew
Symptoms:
Birds-eye spot on berries (anthracnose)
Damping off of seedlings (phytophthora)
Leaf spot (septoria brown spot)
Chlorosis (yellowing of leaves)

8. Symptoms of Fungal diseases

10. Diseases Caused by Mollicutes
Mollicutes are small, polymorphic, wall-less
bacteria that live in young phloem cells of their
hosts; they are generally visible only under an
electron microscope
Symptoms:
Mollicutes symptoms appear as stunting of plants,
yellowing or reddening of leaves, proliferation of
shoots and roots, production of abnormal flowers,
and eventual decline and death of the plant

11. Aster yellow disease caused by
Mollicutes

12. Diseases Caused by Bacteria
Signs (difficult to observe, but can include):
 Bacterial ooze
 Water-soaked lesions
 Bacterial streaming in water from a cut stem
Symptoms:
 Leaf spot with yellow halo
 Fruit spot
 Canker
 Crown gall
 Sheperd’s crook stem ends on woody plants

13. Symptoms of Bacterial disease

15. Diseases Caused by Viruses
Virus can be identified by some procedures.
Virus transmission tests
Fluorescent antibody staining technique
Microscopic examination of infected cells
Electrophoretic tests

16. Signs:
None – the viruses themselves can’t be seen
Symptoms:
Mosaic leaf pattern
Crinkled leaves
Yellowed leaves
Plant stunting

17. Symptoms of Viral disease

18. Noninfectious Diseases
If no pathogen can be found, cultured, or
transmitted from a diseased plant, then it must be
assumed that the disease is caused by an abiotic
environmental factor.
A lack of an essential substance (water, oxygen,
temperature, humidity or mineral nutrients).