GRAIN growers are being encouraged to enact a “monitor and manage” approach to Russian Wheat Aphid for the remainder of spring.
Early detection of RWA is critical for yield loss prevention and the GRDC is urging growers to undertake regular and thorough monitoring in wheat and barley crops.
This follows the detection of RWA in two crops in southern NSW last year and entomologists are calling for growers to monitor crops frequently so any incidences can be identified early and managed effectively.
Look for both white streaking of the leaves and rolled leaves as well as the presence of aphids.Dr Melina Miles, QDAF
Since RWA was first detected on a property in South Australia’s Mid North in May 2016 and became relatively widespread across SA and Victorian grain-growing areas, the GRDC, its research partners and other agencies have been working hard to develop an improved understanding of the pest’s behaviour and suitable integrated management approaches.
An important message emanating from the 2016 experience was that infested crops that were treated to control RWA, recovered to grow and yield normally.
Speaking at recent GRDC Grains Research Updates in northern NSW, QDAF principal entomologist Melina Miles stressed the importance of monitoring crops more frequently than normal to ensure early detection of RWA, should it occur.
“Growers should sample for RWA in the same way they would sample for other cereal aphids,” Dr Miles said. “That is, concentrate on the margins of the field and in areas of the paddock that are stressed (e.g. dry, wet, root disease).
“Look for both white streaking of the leaves and rolled leaves as well as the presence of aphids.
“RWA induce striking symptoms in wheat and barley and within a week or so of being infested, plants will start to exhibit symptoms.
“Plant damage is in response to direct aphid feeding so only the infested leaves and/or tillers show symptoms, some of which are similar to those caused by wheat streak mosaic virus (WSMV) and phenoxy herbicide damage in cereals so close examination of symptomatic plants to determine the presence of RWA is recommended.”
Dr Miles said recommended thresholds were emergence to tillering - 20 RWA per plant; and tillering onwards (Z30-59) – 10 aphids per tiller.
Should control of RWA be required, a current Emergency Use Permit APVMA PER82792 is in place for chlorpyrifos and pirimicarb.
Dr Miles said pirimicarb would kill aphids, but not the beneficial insects in the crop and urged growers to consider pirimicarb as the first option to preserve beneficials which may then suppress further outbreaks.
CLICK HERE for more information on identifying and sampling for RWA.
CLICK HERE to download the GRDC’s popular Crop Aphids Back Pocket Guide, which contains information on aphid monitoring, aphid management (including measures to avoid the risk of insecticide resistance) and biological control.