Anthracnose Caused by Colletotrichum gloeosporioides
Infection occurs leaves, stems, young flowers and fruit
Sunken black spots appear on the surface of the fruit during ripening.
Infection – fruit is usually latent and manifests itself only as the mango begins to ripen
The disease is most severe – in wet weather
sunken black spots infected fruits
Mode of spread and survival:
Inoculum remains on dried leaves, defoliated branches, mummified flowers and flower brackets.
Spread through air-borne conidia
The fungus can enter the pores of green fruits.
The latent infection of mature fruits may take place through lenticles.
The fungus apparently infects the fruits - green and develops in flesh during ripening.
The latent infection is carried from the field to storage.
Epidemiology: The optimum temperature - 250°C and relative humidity from 95 to 97 per cent.
Spray with mancozeb (800 g/kg at 2 g/L) weekly during flowering and then monthly until harvest. Stop spraying 14 days before harvest. During dry weather, flower sprays may be reduced to fortnightly intervals.
Should rain occur during flowering, apply prochloraz (462 g/kg) using 1 g product/L in a tank mix with mancozeb. Prochloraz only needs to be applied every 3-4 weeks.
Copper oxychloride sprays (4 g/L) used for bacterial black spot control also control anthracnose, however copper oxychloride should not be used during flowering. Where bacterial black spot is serious, copper oxychloride can be substituted for mancozeb sprays after flowering.
Dip fruit within 24 hours of harvest by totally submerging them for 5 minutes in hot water (52°C) to which has been added 100 mL product /100 L water. Lowering the temperature of the dip below 52°C will reduce the effectiveness of the treatment.
Temperature must be carefully controlled to within 0.5° to prevent fruit damage. Use an accurate thermometer to monitor temperatures in various parts of the dip during use, especially near the heat source.
Many growers use specially designed tanks heated by gas or electricity with manual or thermostatic temperature control. With an approximate ratio of 3 litres of dip to 1 kg of fruit, no appreciable temperature drop occurs when fruit is added to the tank. This dip also partially controls stem end rot.
Stem End Rot: Lasiodiplodia theobromae
In fruits, the pericarp darkens near the base of the pedicel.
The affected area enlarges to form a circular, black patch which under humid atmosphere extends rapidly and turns the whole fruit completely black within two or three days.
The pulp becomes brown and softer.
Avoid harvesting immature fruit. Postharvest treatment with hot water and carbendazim is partially effective against stem end rot.
For control of stem end rot during controlled atmosphere storage, a dual treatment of hot carbendazim followed by prochloraz is necessary.
Fruit from orchards with a history of stem end rot losses should be rejected for long term storage. The severity of stem end rot can be assessed as follows.
Harvest 100 mature fruit at random from throughout the orchard.
Leave them untreated and store at 25° until they are fully ripe. Ideally, less than one-tenth and certainly no more than one-third of the fruit should develop symptoms of stem end rot by the time they are fully ripe.