NON – PARASITIC DISEASES

Plant diseases in which no foreign organism or parasite is associated are known as non-parasitic diseases. They differ from virus diseases in being non-infectious. Such diseases are induced by certain disorders in the physiology of the plants due to unfavorable environments including the soil conditions.
1. Black Heart of Potato –
Symptoms –
1. The disease usually occurs in poorly ventilated rooms in closely packed conditions.
2. It also occurs in the field when temperature of the soil goes above 320C during growth & maturation of tubers.
3. The disease occurs in the transit when the temperature inside the carrying vans rises for sometime above 320 C.
4. Dark gray to purplish or inky black discoloration occurs in the central tissues of the tuber.
5. In advanced stages, the affected tissues may dry out & separate thus forming cavities.
Remedy –
1. The tubers should not be stored at temperatures above 330 C.
1. Storage of tubers must be made in well ventilated rooms & the bags of tubers should not be piled very high upon each other.
3. In the field if the temperature seems to go very high the field should be irrigated.
2) Black tip or mango necrosis –
Symptoms –
1. The disease is characterized by necrosis of tissues at the distal end of the fruit.
2. The first symptoms is the development of a small etiolated area at the distal end which gradually spreads, turns nearly black, and covers the tip completely.
3. The tip is flattened with the outer skin turning hard & sunken.
4. The inner portion is soft & yields a dark brown liquid due to rotting induced by saprophytic bacteria.
Remedy-
Spray of borax 3-4 kg /500 liters of water at an early stage of fruiting substantially reduces the disease incidence.
3) Tip Burn of Rice –
Symptoms –
1. The first symptom of the disease is the drying of leaves.
2. Leaves show lack of luster & a tendency of bronzing & later become scorched at the tip.
2. The drying progresses down along the margins & finally the whole leaf completely dries.
Remedy –
1. The field should be first drained off in early stage of plant growth & then 30-50 kg/ha of ammonium sulphate is applied.
2. Green manuring could reduce the incidence of disease & increase the yield.
Disease due to lack of minerals –
1. Copper (Cu) – most of the diseases caused by copper deficiency develop symptoms of chlorosis. The leaves may fail to unroll & tend to appear wilted. Leaf margins turn yellow & leaf tips of cereals wither. Citrus trees shows die back symptoms during summer.
2. Zinc (Zn) – Due to deficiency of zinc diseases like rosette of apple, mottle leaf of citrus, and little leaf of grapevine are caused. Leaves of zinc deficient plants develop prominent veins, become pale yellow and sometimes bear dead patches. In rice zinc deficiency causes khaira disease. Leaves of diseased plants show chlorosis at the base. Large number of small brown or bronze spots appears on the lamina surface. The disease can be effectively controlled by 2 sprays of a mixture of 2 kg of zinc sulphate & 1 kg of slaked lime in 400 liters of water per acre.
3. Iron (Fe) – Although plant needs a very small quantity of iron they develop acute chlorosis when this element is deficient in soil or it is not being absorbed by the plant. The chlorosis of leaves without any mottling is the most prominent effect. Soil or foliar application of ferrous sulphate often corrects this deficiency.
4. Manganese (Mn) – Chlorosis of spinach & bean, spots on potatoes & gray speak of oats are common diseases resulting from manganese deficiency. Manganese sulphate may be used as foliar spray to correct this deficiency.
5. Boron (B) – Necrosis of tissues is the most important symptom of boron deficiency. In heart rot of beet the disease is characterized by curling of central leaves, which turns blackish brown & die. In apple fruits, brown necrotic areas in the flesh are caused by boron deficiency. Such deficiencies can be corrected by application of 20kg/ha borax before sowing.