Sclerotinia blight of solanaceous crops

Sclerotinia blight is one of the important diseases of solanaceous crops. It is caused by the fungi of the genus Sclerotinia. The characteristic symptom of this disease is the presence of white fluffy mycelial growth at the point of infection which later turns into black and hard sclerotia.

1. Prepared by: Binita Suwal Sclerotinia Blight in Solanaceous Crops

2. Introduction Etiology : Sclerotinia sclerotiorum Sclerotinia minor Sclerotinia trifolium Hyaline, septate, multinucleated and thin walled hyphae Soil borne and necrotrophic pathogen Host : Legumes, Sunflowers, tobacco, stone fruits, tomatoes and other vegetables Also known as : Cottony rot, white mold, watery soft rot, stem rot, crown rot, blossom blight, S clerotinia rot

3. Symptoms Appearance of a white fluffy mycelial growth in infected plant parts Later, develops into large, compact resting bodies or S clerotia Aerial infection Lesions appear as a water soaked spots that expands irregularly and indeterminately. Affected stems may be girdled, which cause the distal portions of the plant to wilt and then become necrotic . White thick fluffy mycelium develops often both inside and outside the tissue. The cottony hyphae aggregates into pea - sized clumps of mycelium which eventually matures into hard black S clerotia During later stage, the plant tissues appears bleached as compared to normally senescing plant.

4. Symptoms Basal stem infection Occurs when these pathogen infects roots, and/or crown by hyphal or myceliogenic , germination of soil borne sclerotia . Tissues near the soil line shows the symptoms. As the infection spreads, a girdling, basal stem canker is formed within bleached and shredded pith. White cottony mycelium develops on the infected stem surface during the wet weather. Then it spreads to the flowers, petioles, leaves, and stems. The fruit can also be infected, turn grey , and rot.

5. Symptoms Appearance of stem blight near the soil line and the plant start to wilt. Appearance of white fluffy mycelium in which S clerotia develops in later stage.

6. Disease Cycle and Epidemiology Primary source of inoculum: Sclerotia Sclerotia can remain viable in soil for many years. Infestation is high in the areas with high soil moisture, high air humidity and cool temperature Sclerotia germinates and produce white mycelium that cause infection Under low temperature (20-25 ° C) and RH > 80%, Sclerotia germinates and produce apothecia. Ascospore are disseminated by wind. Other source of infection: broad leaf weeds, Internally infected seed or inadequately cleaned seed, mass movement, contaminated machinery, crop debris

7. Management Proper disposal of crop debris. Proper drainage Practice 3-5 year long crop rotation with non hosts such as maize, wheat. Deep ploughing and Soil solarization to reduce soil borne inoculum Plant only certified seed free of Sclerotia and infested seed. Use only resistance variety Avoid excessive irrigation and Nitrogen fertilization. Sclerotia can be separated by mixing in brine solution. Application and incorporation of the beneficial fungus Coniothyrium minitans that infects Sclerotia by reducing their survival, germination and apothecia formation. Use of Biocare –F and Biocare -B Spray Bavistin to check spread of the disease.

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