Diseases of Fruit Plantation Medicinal and Aromatic Crops

Anthracnose disease

Causal organism:Colletotrichum gloeosporoides

• Colletotrichum gloeosporoides is mainly responsible for anthracnose in papaya.
• It belong to the Kingdom-Fungi, Class-Filamentous, Ascomycetes; Order-Phyllachorales.
• The mycelium is branched, sparsely septate and hyaline hyphae. Setae are 1-4 septate and swollen at the base.
• Conidiophores are hyaline and unbranched. The conidia are sub hyaline and variable in shape.
• The sexual spores are the ascospores born on perithecia.
• The perithecial stage develops on stromatoid cushions in which the perithecia are immersed.
• Anthracnose causes considerable losses and is very common in all the papaya growing areas.
Symptoms

• The disease prominently appears on green leaves and also on green immature fruits.
• The symptoms appear in the form of brown to black depressed spots on the fruits.
• The initial symptoms are water-soaked, sunken spots on the fruit.
• The centers of these spots later turn black and then pink when the fungus produces spores.
• The flesh beneath the spots become soft, watery and which spreads to the entire fruit.
• Small, irregular-shaped, water-soaked spots on leaves may also be seen. These. spots eventually turn brown.
• On fruits, symptoms appear only upon ripening and may not be apparent at the time of harvest.
• Brown sunken spots develop on the fruit surface, which later enlarge to form water soaked lesions.
• The flesh beneath the infected portion becomes soft and starts rotting.
 


Epidemiology

• The pathogen is more severe at 25°-30°c and relative humidity of 85-90%.The conidia of pathogen are disseminated by raindrop splashes and insects.
• Disease cycle
• The pathogen is able to survive saprophytically for a considerable period on fallen leaves, petioles and fruits.
• Infection on fruits can take place right from blossoming onwards till their maturity.
• The fungus enters through pores of green fruits where it is still green and develops further inside the flesh during ripening period.
• The pathogen produces ascospores in the senescing petioles which become airborne, lodge on fruit surface, germinate and produce appressoria.
• The pathogen can cause latent infection in mature fruits though lenticels.
• The fungus grows in fruit flesh hydrolyzing sucrose during the course of infection.
Disease cycle

• Mode of spread and survival:
• Primary source of inoculum: The fungus survives as dormant mycelia in the fallen leaves.
• Secondary source of inoculum: Air and rain water splash borne conidia produced in the acervuli.
Management

• The infected fruits should be removed and destroyed.
• The fruits should be harvested as soon as they mature.
• Spaying with Copper Oxychloride (0.3%) or Carbendazim (0.1%) or Thiophanate Methyl (0.1%) at 15 days interval effectively controls the disease.
• Fruits for export purposes should be subjected either to hot water treatment or a fungicidal wax treatment