Citrus black spot: declared pest

Page last updated: Friday, 9 December 2016 - 2:04pm

Please note: This content may be out of date and is currently under review.

Citrus black spot (Guignardia citricarpa) is a fungal disease of citrus trees that can affect external fruit quality. This disease is not known to occur in Western Australia. Early detection and reporting will help protect Western Australian citrus growers.

What plants are affected?

All commercial citrus cultivars are susceptible to citrus black spot (Guignardia citricarpa). The orange cultivar Valencia, mandarins and lemons are the most susceptible.

What do I look for?

Symptoms on the fruit vary, but commonly appear as black spots or blotches. These are grouped into four types:

  • hard spot
  • false melanose or speckled blotch
  • freckle spot
  • virulent or spreading spot.

Hard spot occurs pre-harvest, often as brick-red depressed lesions, with brown or black margins and grey necrotic (dead) tissue in the centre. It often occurs on the side of the fruit exposed to sunlight.

False melanose appears as numerous raised dark brown or black spots (<1mm) and often on green fruit.

Freckle spot is an indication of heavy infection and occurs on mature fruit, most often during storage, postharvest. The spots are round, depressed or sunken and reddish-brown in colour with a red to brown border, 1–3mm in size.

Virulent spot is sunken and irregular in shape and occurs on heavily infected, mature fruit towards the end of the season. The lesions can turn brown to black with a leathery texture that may eventually cover the fruit.

What damage can this pest cause?

Lesions occur only on the rind and do not affect the flesh of the fruit or cause decay. They can reduce produce quality, grade and marketability. Early infection may cause premature fruit drop and reduced yields.

What do I do if I find it?

Guignardia citricarpa is a prohibited declared pest for Western Australia. It is important that suspected disease occurrence is reported. Please contact the Pest and Disease Information Service (PaDIS) to report this pest.

Contact information

Pest and Disease Information Service (PaDIS)
+61 (0)8 9368 3080