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Investigatory Project on Diseases of Crop Plants

A Study of Diseases of Crop Plants of a Particular Area



The plant diseases may be defined as any abnormal physiological or morphological condition which causes a marked disturbance in the plants as a whole or any part of it, induced by certain external agencies. The most important agents which lead to diseases are unfavorable environmental conditions, deficiency of some elements, pathogens etc. Pathogens are the organisms which cause diseases. The various plant diseases delimit the normal growth of crop plants.

Diseases of crop plants will negatively affect the fanning community and ultimately the economy of the society. Hence the study of crop diseases is very important. There are different techniques available for the identification, curing and controlling of these diseases. Materials and Methods


Materials and Methods


Tag, Microscope, Hand lens, knife, scissors, blade etc was collected. Demarcated a local area (name of the place) for the collection and study of diseases of crop plants. The collection trips were arranged in different times of the year. Five diseased crop plants were collected carefully and brought to the laboratory.

With the help of hand lens specimens were examined. The observed symptoms were noted down. Then took thin sections through the affected part of the plant and stained with cotton blue. It was placed on a clean glass slide and mounted in glycerin. The prepared slide of each disease was observed under a compound microscope.

Prepared the herbarium sheets of the major five crop diseases. They were used to obtain information regarding pathogen, symptoms and control measures. Identified the disease and causative organism of each disease, and the symptoms were studied. Control measures for each disease were recommended.


Observation and Results


The identified diseases, their causative organism, host crop plant, and infected plant part are given in the tabular column.


1. Name of the disease – Grey leaf spot of coconut

Causative Organism – Pestalotia Palmarum

Host Plant – Coconut Palm

Infected Plant Part – Leaves


2. Name of the disease – Nut fall of arecanut

Causative Organism – Phytophthora arecae

Host Plant – Arecanut Tree

Infected Plant Part – Leaves inflorescence and nuts


3. Name of the disease – Blast of paddy

Causative Organism – Pyricularia oryzae

Host Plant – Paddy

Infected Plant Part – Leaves and stem


4. Name of the disease – Bunchy top of banana

Causative Organism – Banana virus I

Host Plant – Musa

Infected Plant Part – Leaves and stem


5. Name of the disease – Citrus canker

Causative Organism – xanthomonas citri

Host Plant – Citrus

Infected Plant Part – Stem, leaves and fruits

The identified symptoms of crop plants studied are given below.


1. Name of the disease - Grey leaf spot of coconut

Symptoms – Yellow leision on the surface of leaves. Later these leisions united to form large necrotic patches.


2. Name of the disease - Nut fall of arecanut

Symptoms – Water soaked areas appear on the basal part of the young nuts and leaves. The affected leaves and fruits are subjected to defoliation at an early time.


3. Name of the disease - Bunchy top of banana

Symptoms – The leaves of infected plants get clustered or bunched together at the apex forming "bunchy top". Hence the disease name bunchy top. The leaves become brittle, margins may be rolled spirally. The dwarfing and curling o mature leaves.


4. Name of the disease - Citrus canker

Symptoms – Leisions appear on the lower surface of leaves then spread to the stem and fruits. Leisions rapture and dead area with raised margins is formed. These dead areas are called Canker. Affected leaves and fruits fall off.


5. Name of the disease - Blast of paddy

Symptoms – Appearance of small whitish patches on leaves. They rap-idly enlarge to form spindle shaped areas. Severe infection produces drying out and browning of leaves and presence of "rotten neck" and prevention of filling up of the kernel.


Discussions and Conclusions


Identified the diseases of crop plants and their causative organisms were studied. Bunchy top of banana was a viral disease Citrus canker was a bacterial disease. Grey leaf spot of coconut, Nut fail of arecanut and Blast of paddy were fungal diseases.

Among these, the fungal disease was disseminated by air. The bacterial disease was spread by mechanical implements, insects, rain water etc. An insect Pentalonia nigro - nervosa disseminated viral disease.

The control measures for viral, bacterial and fungal diseases of crop plants were recommended.

1. The viral diseases can be controlled by

a. Spraying insecticides

b. Removing and burning of diseased plants


2. The bacterial disease can be controlled by

a. Removing and burning of diseased plants

b. Growing disease - resistant varieties


3. The fungal disease can be controlled by

a. Spraying fungicides

b. Growing disease - resistant varieties.


All these diseases cause economic loss. Disease resistant varieties are to be produced to overcome these plant diseases.


Viva Questions and Answers


1. What is a pathogen?

The organism which causes the diseases


2. Name the causative organism of citrus canker

Xanthomonas citri


3. What are the symptoms of grey leaf spot of coconut?

Yellow leisions of the surface of leaves, later these patches united to form large necrotic patches.

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