Fusarium Wilt of Cotton

Wilt is one of major disease of cotton, found wherever this crop is grown. It is believed to have originated in Mexico or Central America. In India the disease was reported from Maharashtra, Tamil Nadu, Karnataka and other states. The fungus also infects the other hosts like brinjal, chilli, tobacco and bhendi.

     Etiology

Causal organisum : Fusarium oxysporum f.sp. Vasinfevtum

            The fungus is present both inter and intra cellularly in the host tissue. The mycelium plugs the xylem vessels partially or completely. The macro conidia are 1-5 septate, hyaline, thin walled, linear to falcate, the tepering the micro conidia are hyaline, thin elliptical to spherical, single or two celled.

     Disease cycle

            Fungus can survive in soil as saprophyte for many years. Secondary spread may be through wind, water and other physical and biological agents.

     Symptoms

• Earliest -seedling is the yellowing and browning of the cotyledons.

• Leaves lose their turgidity first turn yellow and then brown and finally drop off.

• The tap root stunted and laterals are less abundant.

• Browning and blackening of vascular tissues.

• Discolorations of leaves starts from the margins and spread towards midribs.

• Wilting may be complete or partial.
  

Yellowing and drying of leaves                 Whole field infected with wilt                             Vascular discolouration

Epidemiology

            The disease was more severe forms in heavy soil with soil temperature 20-30 ⁰C during the crop season.