Brinjal diseases pdf.pdf

Diseases of Brinjal  Phomopsis fruit rot or blight Phomopsis vexans is an important fungal plant pathogen associated with brinjal. Since it is discovered in the year of 1914 but in India, it was reported in 1935 in Gujarat. In India, it occurs in Karnataka, Tami...

Diseases of Brinjal  Phomopsis fruit rot or blight Phomopsis vexans is an important fungal plant pathogen associated with brinjal. Since it is discovered in the year of 1914 but in India, it was reported in 1935 in Gujarat. In India, it occurs in Karnataka, Tamil Nadu, Andra Pradesh, Kerala, Goa, West Bengal, Maharashtra, Madhya Pradesh, Assam, Himachal Pradesh, Uttar Pradesh and Gujarat. The disease is reported to cause 15-20% (30-50% in severe case) yield loss in brinjal. Causal organism: Phomopsis vexans Symptom: Stem symptoms of this fungal disease include brown or dark sunken lesions slightly above the soil surface, and can result in cankers. Seedlings eventually collapse and die. The pathogen attacks leaves but older ones are more susceptible. Lesions are typically circular, gray to brown, and develop a light center. In the center of older lesions, numerous fruiting bodies, called pycnidia, can be observed as small, black pimples, embedded in the host tissue. Affected leaves may turn yellow and drop prematurely. Spots and cankers can form on mature stems and branches. The most important symptoms are on the fruit. Fruit injury begins as a pale, sunken, oval area(s) on the surface. These subsequently enlarge and become depressed. With one lesion or several spots coalescing, large portions of the fruit are affected. Fruit is unmarketable. Soft watery mass Watery decay Mummified brinjal Etiology: Pycnidia with or without beak are found in the affected tissue. They are globose or irregular. Conidiophores in the pycnidium are hyaline, simple or branched. Conidia are hyaline, one celled and sub cylindrical. Ascospores are hyaline, narrowly ellipsoid to bluntly fusoid with one septum. Epidemiology: Disease is favored by hot and wet weather. The optimum temperature for fungal growth is 29˚C and it grows well up to 32˚C.  Mode of survival: The pathogen is seed borne and also survives in plant debris both as mycelium and pycnidia. Seed infections directly lead to diseased seedlings.The pycnidiospores are disseminated through rain splashes, irrigation water, agricultural implements and insects. Management: Prompt destruction of infected plant material to reduce initial inoculum. Plant pathogen-free seed and/or resistant varieties. Transplants should be Phomopsis-free. A 3-4 year crop rotation is beneficial, since the fungus does not infect other crops. Weed control is advisable since pathogen can survive on solanaceous weeds such as nightshades. Fungicides may be warranted and should be done in combination with the above cultural practices.  Sclerotinia blight or rot of brinjal This disease generally observed in West Bengal from the month of December to February in different varieties of brinjal. Sclerotinia blight of brinjal was recorded in the districts of Nadia, North 24-Parganas, Murshidabad, Coochbehar, Jalpaiguri, Dakhin Dinajpur, Birbhum, Hooghly, Purulia of West Bengal, India. Causal organism: Sclerotinia sclerotiorum Symptom: The infection occurred on the stem, branches, leaves and fruits. Primary symptom generally appeared on main stem very close to the soil surface. Water soaked lesion appeared on the stem which gradually increase in length and reached to the base of one or more branches. White cottony mycelial growth covered the major portion of the infected area. Sclerotia developed on the mycelial growth sclerotia were white in at the initial stage, later became more or less black in colour. In the mean time, infection girdle the stem, plant wilted and died. In advanced stages, white, cottony mycelium blankets covered the affected tissue, and sclerotia form on the surface of the fruit. Etiology: The fungus produce white mycelium with hyaline, branched and septate hyphae. Black sclerotia elliptical, near spherical to irregular in shape generally formed. The sclerotia are silvery white in the initial stages of development but turned dark with increasing age of the infection. The pathogen germinate to produce fruiting bodies called apothecia, which are small, thin stalks ending with a cup-like structure about 3–6 mm in diameter. The cup of the apothecium is lined with asci, in which the ascospores are contained. Epidemiology: The pathogen, Sclerotinia sclerotiorum favours moist and cool environments. Under moist field conditions, it is capable of completely invading a plant host, colonizing nearly all of the plant's tissues with mycelium. Optimal temperatures for growth range from 15 -21°C. Under wet conditions, S. sclerotiorum will produce an abundance of mycelium and sclerotia. The fungus also prefers darker, shadier conditions. Disease cycle: The fungus will produce a survival structure called a sclerotium either on or inside the tissues of a host plant. The sclerotia will then remain on the surface of the ground or in the soil, on either living or dead plant parts until the next season. The sclerotium enable the pathogen to survive up to 8 years. Depending on environment, sclerotia germinate to give either mycelia or apothecia. Apothecia produce ascospores, which are the main inoculum source of primary infection in many hosts. Contaminated soil, infected seedlings, and contaminated farm equipment and footware also spread sclerotia or mycelium from the infected to the healthy fields. Management: Minimize the humidity in the foliage by providing adequate spacing during planting. Keep the bed surface dry by providing proper and careful irrigation. Prevent water-logging in the field by preventing uneven surfaces. Remove and properly dispose of the infected plants to reduce the inoculum in the field. Coniothyrium minitans is a commercial biocontrol agent for sclerotinia stem rot. Application of C. minitans should occur three months before S. sclerotiorum development and be incorporated into the soil. Correct use of C. minitans can reduce S. sclerotiorum by 95% and sclerotinia stem rot 10 to 70% Use systemic fungicide whenever necessary. @Dr. Sanchari Roy