Diseases of Chilli

Anthracnose or Die-back and Fruit Rot

Causal Organism:

• Colletotrichum capsici
• Perfect stage: Glomerella cingulata
• Sub-division: Deuteromycotina

Etiology:

• The fungus produces acospore as the primary inoculum and conidia as secondary inoculum.
• Survives in infected plant debris and seeds.
• Spread by rain splashes, wind, and insect vectors.

Symptoms:

• On Leaves:
  • Small, circular to irregular, brownish-black scattered spots.
  • Severe infection causes defoliation (leaf drop).
• On Branches:
  • Infection of growing tips leads to necrosis (death of tissues) from the tip backward.
  • Necrotic areas appear grayish white with black dot-like acervuli at the center.
• On Fruits:
  • Ripe fruits are more susceptible than green ones.
  • Small, circular, yellowish to pinkish sunken spots on fruits.
  • Severe infection leads to shriveling and drying of fruits.
  • Minute black dot-like fruiting bodies (acervuli) form in concentric rings on the lesions.
  • Affected fruits may drop prematurely.

Disease Cycle:

• Primary Infection: Through acospore present in infected plant debris and seeds.
• Secondary Infection: Spread by conidia through rain splash, wind, and insect vectors.

Favorable Conditions: Temperature around 28°C with relative humidity >97%. Humid weather with frequent rainfall.

Management:

• Cultural Practices:
  • Collect and destroy infected plant parts.
  • Collect seeds only from healthy fruits.
  • Remove and destroy Solanaceous weed hosts and infected plant debris.
• Seed Treatment: Carboxin + Thiram @ 2g/kg of seeds.
• Chemical Control:
  • Spray Carbendazim + Mancozeb @ 0.2% at:
    1. Just before flowering.
    2. At fruit formation stage.
    3. 15 days after the second spray.
• Resistant Varieties: G3, G4, B61, Lorai, etc.

Fusarium Wilt

Causal Organism:

• Fusarium oxysporum f.sp. capsici
• Sub-division: Deuteromycotina

Etiology:

• The pathogen produces chlamydospores (thick-walled resting spores) for primary infection.
• Conidia (asexual spores) cause secondary infection.
• Survives in soil, plant debris, and infected seeds.
• Spread through soil, irrigation water, and infected tools.

Symptoms:

• On Plants:
  • Initial yellowing of foliage.
  • Wilting of upper leaves that progresses to a permanent wilt with leaves still attached.
  • Vascular discoloration (brown streaks) in the stem when cut open.
  • Stunted growth and reduced yield.

Disease Cycle:

• Primary Infection: Through chlamydospores in soil or infected plant debris.
• Secondary Infection: Spread by conidia through water, tools, and human activities.

Favorable Conditions:

• Acidic or light-textured soils with poor drainage.
• Temperature range: 20-30°C.

Management:

• Cultural Practices: Use of wilt-resistant varieties. Crop rotation with non-susceptible crops.
• Soil Treatment: Drenching the soil with 1% Bordeaux mixture.
• Seed Treatment: Trichoderma viride @ 4g/kg seed or Carbendazim @ 2g/kg seed.
• Soil Amendment:
  • Mix 2kg T. viride with 50kg FYM, sprinkle water, and cover with polythene.
  • When mycelial growth appears (after ~15 days), apply the mixture in rows for one acre.

Chilli Leaf Curl

Causal Organism:

• Chilli Leaf Curl Virus
• Vector: Whitefly (Bemisia tabaci)

Etiology:

• Virus is transmitted by whitefly (Bemisia tabaci).
• Survives in infected wild hosts and chilli plants.
• Spread occurs through vector movement within and between fields.

Symptoms:

• On Leaves:
  • Curling towards midrib and deformation.
  • Reduced leaf size and shortened internodes.
• On Plant Growth: Stunted growth due to shortened internodes.
• On Flowers and Fruits: Flower buds abscise (fall off) before full growth.
  • Anthers lack pollen grains, affecting fruit set.

Disease Cycle:

• Primary Infection: Through infected wild hosts or chilli plants.
• Secondary Infection: Spread by whitefly as a vector.

Favorable Conditions: High humidity, mild temperature, and low wind speed.

Management:

• Cultural Practices: Uproot and destroy infected plants. Grow resistant varieties.
• Chemical Control: Spray Dimethoate @ 0.2% to control whitefly vector.
• Vector Management: Use yellow sticky traps to monitor and reduce whitefly population.