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Species Page

blue mould

Penicillium italicum


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Host plants / species affected

Main hosts

show all species affected
Citrus aurantium (sour orange)
Citrus bergamia (bergamot)
Citrus limon (lemon)
Citrus maxima (pummelo)
Citrus nobilis (tangor)
Citrus reticulata (mandarin)
Citrus sinensis (navel orange)
Citrus x paradisi (grapefruit)

List of symptoms / signs

Fruit - extensive mould


P. italicum causes a destructive fruit rot of citrus. Early symptoms include a soft water-soaked area on the peel, followed by development of a circular colony of white mould. Bluish asexual spores (conidia) form at the centre of the colony, surrounded by a broad band of white mycelium. The lesions spread more slowly than those caused by P. digitatum. A halo of watersoaked, faded tissue surrounds the lesion. The fruit rapidly spoils and collapses, with sporulation sometimes occurring internally (Brown and Eckert, 1988, Brown, 1994).

Prevention and control

Host-Plant Resistance

Different cultivars of clementine oranges have shown differences in susceptibility to P. digitatum (Farih et al., 1995).

Cultural Control

Minimizing fruit injury and efficient removal of infected fruit are the most effective ways of controlling this disease. Disinfectants can be used to clean equipment in packing and storage facilities. Cull piles should be kept away from the packing area. The disease develops most rapidly at temperatures near 24°C and fruit is thus usually refrigerated during storage. However, P. italicum grows more quickly at temperatures below 10°C than P. digitatum and may predominate in cold storage. The latter is more prone to spreading in packaged fruits than green mould (P. digitatum), forming 'nests' of infection (Brown and Eckert, 1988).

Chemical Control

Due to the variable regulations around (de-)registration of pesticides, we are for the moment not including any specific chemical control recommendations. For further information, we recommend you visit the following resources:

This information is part of a full datasheet available in the Crop Protection Compendium (CPC); For information on how to access the CPC, click here.


P. italicum is prevalent in all citrus-growing regions of the world but less frequent than green mould caused by P. digitatum (Brown and Eckert, 1988).