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.

Description

Aphid species found in cereal crops include:

  • Diuraphis noxia—Russian wheat aphid
  • Metopolophium dirhodum—rose-grain aphid
  • Rhopalosiphum maidis—corn aphid
  • Rhopalosiphum padi—oat aphid, wheat aphid
  • Rhopalosiphum rufiabdominalis—rice root aphid.

Aphid species found in broadleaf field crops include:

  • Acyrthosiphon kondoi—bluegreen aphid
  • Acyrthosiphon pisum—pea aphid
  • Aphis craccivora—cowpea aphid
  • Aphis glycine—soybean aphid
  • Aphis gossypii—cotton aphid
  • Brevicoryne brassicaecabbage aphid
  • Lipaphis erysimi—turnip aphid
  • Myzus persicae—green peach aphid
  • Therioaphis trifolii—spotted alfalfa aphid.

Damage

Rarely cause major damage in most crops. 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.

Control

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.

Further information