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Black citrus aphid

Toxoptera citricida
Black citrus aphid (BCA), also known as brown citrus aphid, is found in citrus growing regions of Australia. In Australia, only four species of aphids are reported to feed on citrus, BCA being one of them. BCA produces large quantities of honeydew which causes a sooty mould to grow on leaves and fruit. Young citrus trees are more susceptible to attack from BCA, with only minor damage occurring in older trees. Overseas, BCA has been linked with the spread of a dieback disease in citrus, caused by citrus tristeza virus.
 
Black citrus aphid - Toxoptera citricida

Description

Adults are shiny, small (2 mm) and black, and can be with or without wings. Nymphs are small (1-2 mm), pear-shaped and range from red-brown to black-brown in colour. The presence of winged adults often indicates food quality has declined, is scarce or that there is overcrowding. In response adults develop wings to fly and find food elsewhere.

Female BCA do not need to mate, instead they lay live young and when temperatures are ideal (>20 °C) nymphs mature within 6 – 8 days. This can happen between 25 – 30 times a year.  BCA populations can increase rapidly with just one aphid having the potential to produce 4400 aphids in three weeks. 

BCA feed on leaves, green shoots and flowers by injecting their mouthpart into plant tissue. Leaves often appear curled, shrivelled or stunted. As BCA feed, large amounts of honeydew is produced which drips onto leaves and fruit, causing a black sooty mould to form and turning leaves and fruit black. The honeydew also attracts ants. 

Control

Natural and beneficial predators such as ladybird beetles, hoverfly larvae, green lacewing larvae and parasitic wasps (Aphidius and Aphelinus) are usually effective at controlling BCA populations. The honeydew produced often provides a good source of food for these natural predators. 

Young citrus trees should be monitored during February and March, and again from September to December and if 25 per cent or more new growth is infested, a registered insecticide should be applied.

Confidor® Guard is a soil-applied insecticide that is registered for use in citrus and provides effective control against many sucking pests including BCA.
 
 

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References

Broughton, S (2007), ‘Aphids in citrus’, Department of Primary Industries and Regional Development (DPIRD), Farmnote 242, https://citrusaustralia.com.au/wp-content/uploads/fn2007_citrusaphids_sbroughton.pdf

Broughton, S (2018), ‘Aphids in citrus’, Department of Primary Industries and Regional Development (DPIRD), https://www.agric.wa.gov.au/citrus/aphids-citrus


PestNet, (Viewed Nov 2019), ‘Citrus aphids’, http://www.pestnet.org/fact_sheets/citrus_aphids_249.htm