Aphids

Toxoptera citricidus - (Black citrus aphid), Uroleucon sonchi - (Brown sowthistle aphid), Brevicoryne brassicae - (Cabbage aphid), Aphis gossypii - (Cotton/melon aphid), Myzus persicae - (Green peach aphid), Lipaphis erysimi - (Turnip aphid), Erisoma lanigerum - (Woolly apple aphid), Rhopalosiphum maidis - (Corn aphid), Nasonovia padi - (Oat/wheat/cereal aphid)

Aphids are common pests across Australia, infesting a wide range of crops including cereals, brassicas (including canola), legumes, citrus, vegetables, stone fruit, cotton, apples and ornamentals. Most species are highly host specific (feeds on one or several closely related genera), however a small number are polyphagous (feeds on a large number of host plants). Typically, aphids become pests during autumn and spring and are the most effective group of insects acting as vectors for plant viruses.

Refer to the links below for more detailed information on different aphid species.

Description

Aphids are small (1-2 mm), soft bodied, pear shaped insects appearing as clusters on plants, particularly growing shoots. Immature forms are wingless and range in colours including green, yellow, orange and black. Most adults are female and do not need to mate. They rarely lay eggs, instead immature nymphs are born and begin feeding immediately. Aphids are generally wingless, however when plants become unsuitable to inhabit or overcrowding occurs, wings develop allowing aphids to migrate.

They are sap sucking pests causing damage to leaves, growing shoots and flowers, and under heavy infestations plant growth rates are reduced. Growing shoots may develop deformed and display stunted growth, and fully emerged leaves can become chlorotic, causing them to wilt and drop from the plant.

Honeydew (sugary sap) is excreted by aphids, initiating a black sooty mould growth on the leaves, branches and fruit, reducing photosynthesis, growth rates and marketability of the plant or fruit. Additionally, aphids are efficient vectors of viruses affecting vegetable, field and ornamental crops. The green peach aphid alone can vector over 100 plant viruses.

Control

Removal of host weeds in and around greenhouses and cropping areas may reduce infestations. Plants should be monitored for pests and damage particularly during autumn and spring when conditions are most favourable.

Encouraging beneficial insects such as ladybird beetles, hoverflies, damsel bugs, lacewings and parasitic wasps may help keep numbers low and minimising the use of broad-spectrum insecticides will allow these beneficial insects to proliferate.

Some species have developed resistance to carbamates, pyrethroids and organophosphates. Aphids produce offspring which are a clone of the mother, consequently, resistant individuals can rapidly take over. Relying solely on insecticides for control is not recommended and the decision to spray should only occur when threshold levels are exceeded.

Related Pests

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.

Brown sowthistle aphid

Uroleucon sonchi

Brown sowthistle aphid is a pest of lettuce crops and is also commonly found on the weed sowthistle. They are regularly confused with the cowpea aphid, as they are often present in winter pulse crops where sowthistle weeds are present. Brown sowthistle aphids, unlike cowpea aphids, will not colonise winter pulses and are significantly bigger. Brown sowthistle aphid can transmit cucumber mosaic virus (CMV).

Cabbage aphid

Brevicoryne brassicae

Also known as grey cabbage aphid, cabbage aphid is a pest to both horticultural brassica and broadacre canola crops. In addition to feeding damage, it is a virus vector transmitting cauliflower mosaic virus (significant in horticulture), turnip mosaic virus (significant in canola) and beet western yellow virus.

Corn aphid

Cotton aphid

Aphis gossypii

Cotton aphids are pests of broadleaf crops, including cotton where it is the most common aphid pest. In addition to causing feeding damage, they are virus vectors transmitting cotton bunchy top disease in cotton. Also, the honeydew which is secreted by aphids can cause sooty mould to develop and in cotton, it can contaminate lint when the bolls start opening.

Cotton aphid is also known as melon aphid in horticultural crops. It can be a major pest of cucurbits where large populations can cause the growing tips and leaves to die. Like in cotton, melon aphid also transmits many viruses including cucumber mosaic virus, papaya ringspot virus and bean common mosaic virus while it is feeding.

Currant lettuce aphid

Nasonovia ribis-nigri

Currant lettuce aphid (CLA), also known as lettuce aphid, is a significant pest of lettuce, as well as endive and chicory. CLA is primarily known to contaminate produce by colonising in the inner leaves, which deems it unmarketable. CLA can attack hosts at any stage of development and are known to transmit cucumber mosaic virus (CMV). Other hosts include gooseberry and red, black and white currants.

Green peach aphid

Oat Wheat aphid

Turnip aphid

Woolly aphid

Eriosoma lanigerum

A major pest in every apple-growing area of Australia. As well as damaging the fruit, they can affect every part of an apple tree and reduce its overall health.

References

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

Department of Primary Industries and Regional Development (DPRID) (2018), ‘Aphids, mealybugs and scales’, https://www.agric.wa.gov.au/control-methods/aphids-mealybugs-and-scales

GRDC (2015), ‘Resistance management strategy for the green peach aphid in Australian grains’, https://grdc.com.au/__data/assets/pdf_file/0023/117275/resistancemanagementstrategygpa.pdf.pdf

Manners, A (2016), ‘Aphids - A Rapidly Reproducing Problem’, Horticulture and Innovation Australia, https://www.horticulture.com.au/globalassets/hort-innovation/resource-assets/ny15002-aphids-rapidly-reproducing-problem.pdf

Umina, P and Hangartner, S (viewed Oct 2019), ‘Cabbage aphid’, Cesar Australia, http://cesaraustralia.com/sustainable-agriculture/pestnotes/insect/Cabbage-aphid