Crop Diseases

Plant diseases are improvement because of the loss they cause. In the history of mankind plant disease have played an important role. A good example would be the Irish potato famine caused due to late blight of potato, a disease affecting the potato crop.

Classification of plant diseases

Plant disease may be grouped as seed - borne, soil borne or air borne. When the disease spreads through seed, soil, or through wind.

Symptoms of plant diseases

1. Mildew Pathogen seen as a growth on the surface of the host.

2. Rust Small pustules of spores, usually breaking through the hoot epidermis.

3. Smuts Pustules larger than those of the rusts.

4. Scab Roughed appearance of the diseased organ.

5. Colour change Change of colour from the normal.

6. Hypertrophy Abnormal increase in the size of one or more organ due to presence of diseased pathogens.

7. Hypoplasia Inhibition of growth resulting in stunting or dwarfing.

8. Necrosis Death of cells tissue and organs as a result of parasitic activity.

9. Canker Dead area in the bank or cortex of the stem.

10. Blight Burnt appearance

11. Wilt Succulent parts lose their turgidity, become flaccid and droop.

12. Die back Drying of plant organs from the tip backwards.

Control of Plant Diseases

Physical control methods

1. Quarantine regulations - Entry of diseased plants should be prevented.

2. Field sanitation - To destroy completely or partially the source of infection present in the soil. This is done by

a) removal of diseased plant debris and their burning.

b) use of chemical.

c) crop rotation.

d) proper spacing between plants

e) mixed cropping

f) deep ploughing to expose the resting spores.

Chemical control methods

A number of chemicals are available depending upon the nature of pathogens many types of pesticides are used, which may be differentiated into fungicides, bactericides, insecticides, nematicides, herbicides etc.

Immunisation control methods

Immunity means the resistance of the host to infection and disease development. It is most effective and definite method of protecting a crop against the disease. It involves the developing and growing of disease resistant varieties of crop plants.