Agrotechnology

Collar rot and web blight caused by Rhizoctonia solani Kuhn in vegetable cowpea (Vigna unguiculata (L) Walp.) and its organic management

2^nd International Conference on Agricultural & Horticultural Sciences

Radisson Blu Plaza Hotel, Hyderabad, India February 03-05, 2014

Sivakumar Vavilapalli, Celine V A and Girija V K

Posters: Agrotechnol

Abstract:

Vegetable cowpea ( Vigna unguiculata (L) Walp.) is one of the most popular and nutritious leguminous vegetable traditionally grown in the humid tropics of Kerala. Though the crop is gaining importance with the farmers, it is attacked by many fungal, bacterial and viral diseases. Among the diseases, collar rot and web blight caused by Rhizoctonia solani Kuhn is the most serious soil borne disease in Kerala due to environmental conditions like high temperature and humidity causing severe yield loss. This ubiquitous fungus is highly virulent in cowpea causing stand loss and subsequent yield loss. Collar rot is most severe at seedling stage and web blight is severe at vegetative stage. As it has wide host range, it is difficult to develop disease resistance. The collar rot is characterized by oval or spindle shaped brown-black lesions having length ranging from 0.2-8 cm at soil level near collar region, girdling the basal portion of the stem. The leaves turn yellow followed by shedding of leaves and finally the entire plant wilts. In affected plants root development is poor. White mycelial growth often studded with small sclerotia was seen on basal part of the affected stem. Web blight symptoms appear on leaves as small circular, light grayish brown spots which later enlarge. The affected regions were surrounded by irregular water soaked area. On leaves also there is mycelial growth accomplished by sclerotial formation over the affected areas. Cobweb like symptoms also noticed on the leaves and hence the name. Different plant oils, oil cakes, indigenous materials like turmeric power-baking soda, rice husk ash is effective in controlling R.solani causing the disease. Bio-control agents like Trichodermaharzianum, Pseudomonas fluorescens can also be used to manage R.solani.