Cereal aphids and cowpea aphids are now active. Are you still checking for the Russian wheat aphid?
Plant pathologist Andrea Hills (DPIRD) has reported finding corn and oat aphids in a paddock that was sown very early with serradella and barley (variety unknown) for sheep feed near Gibson. More than 60% of the barley tillers were infested.
Corn aphids are light green to dark olive green with darker patches at the base of the tube –like projections (siphuncles) on either side at the rear of the body. Corn aphid colonies are often difficult to detect because they usually develop within the furled leaves of tillers any time from seedling to head emergence.
Oat aphids are the most abundant species of cereal aphids and vary from mottled yellow-green through olive-green and dusky brown, to a blackish green and are characterised by a reddish patch on the tip of the abdomen.
Oat aphid colonies develop on the outside of tillers from the base upwards on stems, nodes and backs of mature leaves, starting any time between seedling stage and grain filling.
Cereal aphid adults and nymphs suck plant sap with large populations limiting grain yield and size, especially with winter and spring infestations. Cereal aphids also spread barley yellow dwarf virus that reduces cereal yield.
For more information on aphids refer the department’s Diagnosing cereal aphids page.
- Grass Patch
Plant pathologist Andrea Hills (DPIRD) has found cowpea aphids in a vetch trial near Grass Patch. The vetch plant growth stages ranged from emergence to first flower. Up to 80% of plants were infested.
Andrea has also reported that cowpea aphids have recently been damaging faba beans in a trial at the department’s research station at Gibson. The number of aphids was large enough that the trial was sprayed with an insecticide.
Cowpea aphids are usually easily spotted by the shiny black colour of the adults, nymphs are a dull grey, and the dense clusters they form on a few plant growing points. On close inspection with a magnifying lens their black and white legs are also a good identification feature.
The cowpea aphid's host range includes pasture medics, faba beans and tree lucerne.
Cowpea aphids are known to transmit several plant viruses that can contribute to yield losses, including cucumber mosaic virus, bean yellow mosaic virus, alfalfa mosaic virus and pea seed-borne mosaic virus.
For more information on these aphids refer to cesar’s Cowpea aphid PestNote.
Growers and consultants are urged to check for the Russian wheat aphid
The Russian wheat aphid (Diuraphis noxia) (RWA) has not been detected in WA yet and cereal growers, consultants and agronomists are encouraged to continue to check paddocks for signs of this aphid during the growing season.
Remember, if you are unsure of what aphid species you are finding in your crops you can use the PestFax Reporter app to attach up to three images of the aphid(s) and request that a department entomologist identify or confirm the aphid species via an email or phone response.
For a list of insecticides registered for use on aphids see the department’s 2017 Winter/Spring Insecticide Guide.
For more information on aphids refer the department’s 2017 Protecting WA Crops Issue 3 newsletter Aphids – WA’s insect problem children.
For more insect information contact Svetlana Micic, Research Officer, Albany on +61 (0)8 9892 8591 or Dustin Severtson, Development Officer, Northam on +61 (0)8 9690 2160 or Alan Lord, Technical Officer, South Perth on +61 (0)8 9368 3758.