Aphids

A wide range of aphid species can affect field crops. Most are small, with oval-shaped green, brown or black bodies. They often form colonies.

Aphids suck on sap, causing loss of vigour, and in some cases yellowing, stunting or distortion of plant parts. Honeydew (unused sap) secreted by the insects can cause sooty mould to develop on leaves. In crops such as cotton, the honeydew affects fibre quality. Aphids can also be vectors (carriers) for viruses.

Scientific name

Aphid species found in field crops include:

Acyrthosiphon kondoi (bluegreen aphid)
Brevicoryne brassicae (cabbage aphid)
Rhopalosiphum maidis (corn aphid)
Aphis gossypii (cotton aphid)
Aphis craccivora (cowpea aphid)
Myzus persicae (green peach aphid)
Rhopalosiphum padi (oat aphid, wheat aphid)
Acyrthosiphon pisum (pea aphid)
Rhopalosiphum rufiabdominalis (rice root aphid)
Metopolophium dirhodum (rose-grain aphid)
Diuraphis noxia (Russian wheat aphid)
Aphis glycine (soybean aphid)
Therioaphis trifolii (spotted alfalfa aphid)
Lipaphis erysimi (turnip aphid)

Damage

Rarely cause major damage in most crops.

Control measures

Control measures are usually not warranted, as a range of parasites and predators keep population numbers down. Exceptions may be where:

  • the crop is under moisture stress
  • heavy populations are observed
  • virus outbreaks are likely to be a problem.

More information