Disease:Amaranthus leaf blight mosaic

Rhizoctonia solani

This is the most important disease affecting amaranthus in all the areas where the crop is cultivated in Kerala.

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Symptoms

  • The diseases starts off as small straw coloured lesions in the foliage of young plants which later coalesce and turn greenish and often get dislodged from the leaf lamina causing shot holes and disfiguring it entirely.
  • The basidiospores of the pathogen formed in large numbers on the under side of the infected foliage as white powdery coating, causes spread of the disease under field condition.
  • The infected foliage cannot be marketed and thus reduces the commercial value of the crop considerably.

Procedure for Observation

Randomly select 20 plants and look for the symptom.

ETL

  • Mere presence

    • Control Measures

  • The green type, CO -1 is resistant to the pathogen and it can be used as crop mix to reduce the spread of the pathogen under field conditions.
  • Prophylactic spray application of baking soda with turmeric powder at a ratio of 1: 4 can give rise to systemic induced resistance in the plants.(Dissolve 40 g of Asafoetida (Palkayam ) in 10 lit of water. To this add 8 g of sodium bicarbonate and 32 g of turmeric powder with violent agitation . Filter and spray)
  • Fungicidal control can be effectively done by the periodic application of mancozeb@ 4g/L using cowdung supernatant as the diluent.
  • Cowdung supernatant can be prepared by dispensing 1kg of fresh cowdung in 10L of water and taking the supernatant after sieving through fine muslin cloth. The fungicidal solution has to be prepared in the cowdung supernatant and sprayed as fine droplets on to the under side of the foliage. This spraying has to be discontinued 14 days before harvesting of the crop to minimize residue problem.
  • Spraying 2 % Pseudomonas also effective in managing the disease.