Diseases of Fruit Plantation Medicinal and Aromatic Crops

Anthracnose

Causal organism: Gloeosporium psidii Delacr. (Perfect stage: Glomerella psidii (Del.) Sheld.)
Symptoms

• The disease attacks all plant parts except roots.
• Severity of the disease may show die-back of the main branches resulting in death of plants.
• The most characteristic symptoms appear as small pin-head sized spots on the unripe fruits during the rainy season.
• The spots gradually enlarge to form sunken,circular, dark brown to black spots.
• The infected area of the unripe fruits become harde and corky.
• Acervuli are formed on fruit stalks.

Pathogen

• Conidia are hyaline, aseptate, oval to elliptical or straight, cylindrical, obtuse apices or flattened at base. Conidiophore is cylindrical and tapering towards apex.
• It is hyaline and septate with single terminal phialide. Acervuli are dark brown to black.

Epidemiology

• The cool season (Jan - Mar) and the hot, dry weather (Apr-Jun) prevent the spread of infection.
• In moist weather, acervuli are produced in abundance on dead twigs with pinkish spore masses. Conidia initiate fresh infection.
• The temperature for disease development on fruits ranges from 30 to35°C.

Mode of spread and survival

• The pathogen remains dormant for about three months in young infected fruits.
• It becomes active and incites rotting when the fruit begins to ripe. In moist weather, acervuli appear as black dots scattered throughout the dead parts of the twigs.
• From the twigs, the fungus penetrates the petioles and attacks young leaves, which become distorted with dead areas at margins or tips. The conidia are spread through wind or rain.
Management

• Spraying the trees with Bordeaux mixture (1.0 per cent) or copper oxychloride (0.2 per cent) or Carbendazim (0.1%) before the onset of monsoon reduces disease incidence.
  
• Apple Guava (light red fleshed) is moderately resistant to anthracnose.