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).

Refer to links below for more aphid information.

Description

Adult brown sowthistle aphids are wingless and considered one of the largest aphids, measuring 3-4.5 mm long. They are shiny in appearance and are dark reddish-brown in colour. Nymphs are yellow-green to pale brown in colour. Damage is caused by sap being sucked from the leaves resulting in distortion, wilting and in severe cases shrivelling of the whole plant.

Control

Removal of host weeds, in particular sowthistle, is an important control measure. Monitoring crops and applying a foliar insecticide spray is recommended once numbers reach threshold levels.

Movento^® is registered for use in lettuce for control of brown sowthistle aphid. It is considered ‘soft’ on most beneficial species and therefore, when used as directed, has less impact on beneficial species compared to other broad-spectrum control options.

Related Pests

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.

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.

Green peach aphid

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.

Turnip aphid

References

Bayer CropScience, ‘Users Guide for lettuce. Controlling aphids in field grown lettuce with Movento® and Confidor®’, https://resources.bayer.com.au/resources/uploads/Bulletin/file9131.pdf

GRDC Grownotes (2017), ‘Faba Bean’, Section 7 Insect Control p 10-11 https://grdc.com.au/__data/assets/pdf_file/0031/369526/GrowNote-Faba-Bean-North-7-Insect-control.pdf

Ekman, J, Tesoriero, L, and Grigg, S (2014), ‘Pests, Diseases and Disorders of Babyleaf Vegetables. A Field Identification Guide’, Applied Horticulture Research
http://ahr.com.au/wp-content/uploads/2015/03/AHR_Babyleaf_Proof3.pdf