Diseases of fruit plantation medicinal and aromatic crops (2+1)

Leaf spot

Causal Organism: Colletotrichum capsici (Petch)
Symptoms

• The spot on the leaf is irregular in shape & size, light to dark brown surrounded by diffused chlorotic yellow hallow, marginal leaf tissues become black, necrotic and gradually spread to the leaf centre.
• Occasionally diffused yellow halo may also be seen.
• Fungus produces Acervulus, the asexual fruiting body where the circular, black lesions that occur rapidly increase in size and girdle the stem culminating in the death of the vine.
• Later on the fungi move to the spikes of individual plants.


Etiology

• The pathogen is having septate mycelia with inter and intracellular haustoria.
• Sexual spores are the ascospores borne in ascus and the asexual spores are Conidia borne in sporangia.
• They mainly survive as a dormant mycelia and spread through air and soil borne conidia.
• Primary source of inoculum: Ascospores borne in ascus and the chlamydospores. Sexual fruiting body is perithecia
• Secondary source of inoculum: Air and soil borne conidia
• Spread through air and soil borne conidia
Epidemiology

• The fungi require a Temp of 30-32⁰C, relative humidity 90-95% and the susceptible host for the occurrence of the disease.
Life Cycle
Management

• At initial stage, infected leaves, spikes should be collected and destroyed. Early diagnosis of the disease and spray with Carbendazim (1%) or Companion (0.2%) has been found to be effective.
• Low nitrogen and increased potassium content in the soil make the plants more resistant to this disease. Application of Trichoderma viridae, a biocontrol agent along with FYM in the soil.
  
• Destruction of disease debris and spraying the plants with Bordeaux mixture ( 0.5%). Cuttings for planting should always be taken from disease free and healthy vines.