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

Post harvest diseases of Citrus

Post harvest diseases

Green / Blue mold rot
Causal organism: Penicillium digitatum and P. italicum

• Green/Blue mold are common post harvest diseases of all the citrus growing areas of the country, particularly those with a cooler climate or those which use cold storage for citrus fruits.
Symptoms

• The first symptom is the appearance of soft, watery spots measuring 5-10 mm in diameter.
• Soft water soaked areas develop on the skin of the fruit which soon become covered with white mould in both the cases. Coloured spores are formed at the centre of the lesions. In green mould rot, whitish margin is generally not more than 2 mm in diameter. These two moulds appear frequently during transportation and storage. But the green mould generally dominates as it grows rapidly at moderate temperature. Insect injury, especially with mediterranean fruit fly when the fruits are still on the trees causing undetectable pre-harvest infection and also the bruises caused during harvesting and handling are the predisposing factors.
• The decayed fruit becomes soft and shrinked in size. In humid atmosphere, the infected fruit also becomes attacked by other molds and bacteria, which soon turns into a rotten mass.
Epidemiology

• Green mold tends to develop rapidly at temperatures around 24⁰C.
  
• Growth is much slower if temperature rises above 30⁰C.
  
• It is particularly common on fruits harvested in the middle of the season.

Mode of spread

• The fungus survives in the orchard from season to season in the form of conidia. Infection is mainly through airborne spores which enter the skin of the fruit bearing small injuries or blemishes.
• It can also invade the fruits which is damaged on the tree due to chilling injury. Infected fruit in storage do not infect other fruits packed around.
• However, infected fruit may liberate abundant green fungal spores which spoil the skin of adjacent fruits.
• Since it attacks only the injured fruits, the best way to prevent green mold attack is to handle the fruits carefully during and after harvest.