Aphids are active in canola, cereal and lupin crops, but beneficial insects are also present
Brent Pritchard (Farmanco) has found cereal aphids on self-sown barley at Wellstead.
Plant pathologist Andrea Hills (DPIRD) has reported finding corn aphids in a Rosalind barley crop at stem elongation near Scaddan. The aphids were on the crop edge.
The two main cereal aphids in WA are corn aphids and oat aphids.
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.
It is important that growers and consultants continue to monitor WA cereal crops for the Russian wheat aphid (RWA). This pest has not been found in WA. In addition to feeding damage it can inject toxins into cereal plants further stunting them and reducing yields. For more information on RWA refer to the department’s Diagnosing russian wheat aphid and Biosecurity alert - Russian wheat aphid pages. For more tips on how to identify RWA view cesar’s recently released Russian wheat aphid identification video.
Parasitised aphids in canola crops
- South Stirlings
Chris Robinson (Farmanco) has found aphids parasitised by wasps in a 5-10% flowering canola crop at Kojonup.
Brent Pritchard (Farmanco) reports finding low levels of aphids which have been parasitised by wasps on flowering spikes of canola at South Stirlings and Gairdner. Crops were at 10-50% flowering.
Growers and consultants are urged to check crops for beneficial insects and insect fungal infections in crops before deciding to invest in an insecticide spray. Beneficials include predators (ladybirds, hoverfly larvae and lacewing larvae) and parasitic wasps. These are a common form of aphid control during the warmer days of spring and when low to moderate numbers of aphids are present but they have less impact on heavy infestations of aphids. For more information, see the department’s Know what beneficials look like in your crop page.
For more information on identifying and managing canola aphids refer to the DPIRD’s;
- Aphid management in canola crops page
- Diagnosing canola aphids page
- 2017 Protecting WA Crops Issue 3 newsletter Aphids – WA’s insect problem children
- Aphids in your crops YouTube video.
Blue green aphids in lupins
David Stead (Anasazi Agronomy) reports that blue green aphids are present in lupins at Cadoux. David commented that they seem to be colonising the lupins plant where there have been, or still are, patches of uncontrolled lucerne flea.
The three most common aphid species which attack lupins are cowpea aphid, bluegreen aphid and green peach aphid.
Cowpea aphids are usually easily spotted by their black colour and dense clusters 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 bluegreen aphid is the largest of the three common species, measuring up to 3mm long. Both the winged and wingless forms are a matte bluish-green, similar in colour to the mature leaves of narrow-leaf lupins.
The green peach aphid (GPA) varies in colour from shiny pale yellow-green to mid-green, orange or pink. The yellowy-green GPAs are similar in colour to young unfurled lupin leaves. The winged GPAs have a dark patch on their backs.
Aphids can damage lupin crops through both feeding damage and virus transmission (cucumber mosaic virus and bean yellow mosaic virus).
The spray threshold for control of aphids on lupins is for more than 30% of flowering spikes to have 30 or more aphids. Consideration should also be given to potential crop yield.
For more information refer to DPIRD’s Identification of aphids in lupin crops and Management of aphids in Western Australian lupin crops pages.
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 2019 Winter/spring insecticide guide.
For more aphid information contact Dustin Severtson, Development Officer, Northam on +61 (0)8 9690 2160, Alan Lord, Technical Officer, South Perth on +61 (0)8 9368 3758 or Svetlana Micic, Research Officer, Albany on +61 (0)8 9892 8591.
Article authors: Cindy Webster (DPIRD Narrogin) and Alan Lord (DPIRD South Perth).