Diseases and Management of Crops under Protected Cultivation

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(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 -
(Diseases and Management of Crops under Protected Cultivation) • To kill all the Pythium spores, a concentration of iodine of 5 ml/1000 L was needed for 30 minutes or 10 ml/1000 L was needed for 5 minutes • The Fusarium is basically twice as tough. To kill all the Fusa rium spores, a concentration of iodine 20 ml/1000 L was needed for 5 minutes In general hydroponic system needs prevention and following steps are essential for management of different diseases. To prevent disease • The hydroponics facilities undergo constant cleaning with the removal of all waste materials, plant waste, algae on floors and walls and water on the floors. • Diseased foliage should be promptly cut from plants and removed from the growing area along with other waste material • To prevent disease ingress, the nutrient solution, medium and roots should be regularly sterilized. • No-one who has been handling fresh fruit and vegetables can enter hydroponics without first washing their hands and changing their clothing • Smokers cannot enter the facility unless they have washed their hands and replaced their clothing. Tobacco can carry the mosaic virus which afflicts tomatoes and capsicums • Daily monitoring for introduced invertebrates, fungi and disease is carried out. • ‘Sterilizing agents’ must yield a ‘residual’ chemical when dissolved in the working nutrient solution so that the entire system is treated each time plants are watered. • There are a variety of disinfectants available for hydroponic systems. “Oxidizing agents” have historically been most popular. They include • Chlorine dioxide • Sodium hypochlorite • Monochloramine • Hydrogen peroxide • UV and ozone. • However, monochloramine has the advantage of possessing a long half-life, is gentle on roots, and is compatible with the majority of 'organic' mediums and growth promoters. Biological control in hydroponic system • Biocontrol would seem to be ideally suited for soilless systems in closed structures. Environmental conditions in greenhouse are more uniform and can be adjusted to make conditions favourable for the growth of biocontrol agent and unfavourable for the pathogen. Due to lack of competition from other microbes as of soil biocontrol is result oriented in hydroponic systems. • Fluorescent pseudomonas has been used against Fusarium wilt of carnation (Dianthus caryophillus L.) - 146 -
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CENTRE OF ADVANCED FACULTY TRAINING
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CONTENTS Sl. No. Title Speaker Page
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REMARKS by Dr. K.S. Dubey Director
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and extension literature that have
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discussions. No doubt the course is
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Introduction (Diseases and Manageme
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Loads For Greenhouse: (Diseases and
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Chemical Control Chemical Abamectin
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4. High value off season vegetable
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ANNEXURE-I CENTRE OF ADVANCED FACUL
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9. Dr. (Mrs.) T.K.S. Latha Assistan
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TRAINING ON ANNEXURE-III DISEASES A
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ANNEXURE-IV CENTRE OF ADVANCED FACU
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14:30-17:00 hrs Visit to VRC for pr
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Sunday 23.9.2012 Monday 24.9.2012 1
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