Diseases and Management of Crops under Protected Cultivation

(Diseases and Management of Crops under Protected Cultivation)
• Stunting
• Yield loss
Common diseases are
Gray mold (botrytis)
Botrytis cinerea is the causal agent of gray mould. It is a common fungus, with a very wide
host range and can persist in the hydroponic cultures year-round as mycelium, conidia, or as
sclerotia on living or dead tissue. If the humidity goes beyond 85% and air circulation lowers down
the fungus produces a large amount of spores on the plant surface, germinate, and penetrate the
host plant. Cutting stubs are particularly susceptible to gray mold infection. Fungal symptoms are
characterized by the presence of fluffy, gray/brown mycelium that produces a cloud of spores if
disturbed. Affected tissue is soft and brown, and sometimes has a water-soaked appearance.
Environmental control inside hydroponic system is the best remedy for the gray mould. To control
the spores of the fungus the relative humidity should be maintained below 85%.A good aircirculation,
ventilation and adequate plant spacing are the appropriate ways of controlling the
fungus.
Powdery mildew
Powdery mildew are well defined family of obligate parasites grow abundantly on foliage of
the angiosperms and damage wide variety of crops. In hydroponic system the severity reflects with
white spots, necrosis, chlorosis and death. Use of silicon, as potassium silicate, at 100 mg L-1 at
3.9-4.0 mS/cm EC of nutrient solution reduced the incidence of powdery mildew significantly in
tomatoes .
Wilts
Verticullum Wilt and Fusarium Wilt- Wilt diseases start as small spots on the leaves of
tomato, peppers or eggplants. The lower leaves start to curl up, dry out and wilt. Sometimes,
portions of the plant may wilt suddenly. These can be prevented by using only fresh, clean
medium for each planting, and using resistant varieties of tomatoes
Tobacco mosaic virus
TMV remains on tobacco leaves for years.It can be introduced the hydro garden by the
hands of smokers. Smoking in the grow room is not allowed.Smokers must wash their hands
thoroughly with soap and water before touching anything in your garden area.
Role of iodine in hydroponic cultures
Iodine is a dark, dense, crystalline solid (4.96 g/ml) at room temperature, which slowly
dissolves in water to form a concentrated solution (in equilibrium with its crystallised form) of
approximately 250 ppm (0.25g/litre). Iodine is a potent broad-spectrum biocide, even at low
concentrations (1–2ppm). When in contact with micro-organisms such as bacteria, viruses,fungi
and protozoa, iodine is able to rapidly penetrate the cell wall and oxidise a number of critical
components within the cell. The combined effect of these oxidative reactions is cell death.
- 145 -