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Virus surveillance and aphid monitoring findings

A canola plant in the Northam region displaying Turnip yellows virus symptoms.
A canola plant in the Northam region displaying Turnip yellows virus symptoms. Photo courtesy of: DPIRD.

In mid to late September, the Department of Primary Industries and Regional Development’s (DPIRD’s) grains virology team travelled to 64 crops in the Geraldton, Kwinana West, Esperance and Albany port zones. The team collected plant samples from canola, cereals and pulse crops and tested them in the laboratory using a series of diagnostic assays to detect the presence of viruses. Specifically, cereals were checked for barley yellow dwarf virus, cereal dwarf virus and wheat streak mosaic virus. Canola underwent testing for turnip yellows virus (TuYV) and turnip mosaic virus. Pulses were tested for a range of viruses including cucumber mosaic virus, bean yellow mosaic virus and pea seedborne mosaic virus.

This surveillance activity is part of a 5-year GRDC funded project titled “Effective virus management in grains crops” (DAW2305-003RTX). One component of the project is to better understand the prevalence of known disease-causing viruses in cereal, canola and pulse crops.

Green peach aphid infestation on a canola leaf.
Green peach aphid infestation on a canola leaf. Photo courtesy of: DPIRD.

To complement this virus surveillance work, DPIRD also conducted green peach aphid (GPA) and TuYV monitoring using sticky traps set next to canola crops in the Northam, Albany and Esperance regions. This activity was developed in previous DPIRD Boosting Grains projects and will be continued as part of the new GRDC investment. Trapping was conducted from crop emergence to the beginning of flowering. Winged aphids caught in the traps were counted, analysed under a microscope to identify GPA, and then tested for TuYV using molecular diagnostic technology. Additionally, these canola crops were inspected for the presence of GPA at the 6 leaf stage and the beginning of flowering. The crops were also tested for the rate of TuYV infection. Several of these crops were included in the virus surveillance program mentioned above. The Esperance sites were managed by South East Agronomy Research (SEAR).

Surveillance findings

TuYV was the most prevalent virus, found in 84% of the canola crops sampled. Infection levels were highest, reaching up to 95% in a single crop, in the Albany port zone. Average canola TuYV infection rates were highest in the Albany region (40% plants infected), followed by Northam (30%) and Geraldton and Esperance (both 2%). GPA, the vector of TuYV, was found in all the canola crops surveyed. TuYV was also detected in a field pea and faba bean crop, both at low infection levels, in the Esperance region.

Canola crops sampled for turnip yellows virus infection rates in each crop.
Canola crops sampled for turnip yellows virus infection rates in each crop. Map courtesy of: Christiaan Valentine (DPIRD).

DPIRD’s aphid monitoring program supported these findings, as GPA was detected earlier in the Albany (early May) and Northam (mid-May) regions compared to the Esperance region (late July). Results from aphid monitoring were communicated throughout the 2023 growing season in the PestFacts WA newsletter. You can read these articles in Issue 6 Green peach aphid alert, Issue 7 Green peach aphid and turnip yellows virus update, Issue 10 Turnips yellows virus detected in flying green peach aphids and in canola and Issue 13 Turnip yellows virus is spreading in canola in Kwinana West and Albany port zones.

However, minimal levels of TuYV infection were detected at the aphid monitoring sites from mid-July to early August, and significant numbers of TuYV-carrying GPA were not detected until early August. This suggests that exponential levels of spread occurred between early August and mid-September in the Northam and Albany regions. Therefore, in these regions, crops that were sown later and matured later were more likely to have significant levels of spread prior to flowering, which is associated with higher yield losses.

No viruses were detected in the 27 cereal crops that were sampled, despite the presence of oat aphids, which are known to be primary vectors of yellow dwarf virus.

Twelve pulse crops (3 lupin, 3 faba bean, 4 lentil, 1 field pea, 1 vetch) were tested and the only viruses found were TuYV and soybean dwarf virus.

Free pulse seed testing for virus infections

DPIRD is offering free seed testing for virus infections, with a focus on cucumber mosaic virus (CMV) in lupins and lentils, as well as pea seedborne mosaic virus (PSbMV) in field peas. The DPIRD team will conduct thorough testing, and results will be delivered before the 2024 seeding season.

Growers who are interested in using this free service need to email DPIRD Research Scientist Dr Nazanin Nazeri (Nazanin.Nazeri@dpird.wa.gov.au) and request the seed testing form.

More information

For more aphid and TuYV information, refer to DPIRD’s:

For further information contact Research Scientist Benjamin Congdon, South Perth on +61 (0)8 9368 3499.

 

 

Article author: Benjamin Congdon (DPIRD South Perth).