Beet Western Yellows Virus (BWYV) update
Beet Western Yellows Virus (BWYV) is widespread in canola crops across South Australia, the
Victorian Mallee and Victorian Wimmera and a few reports have also come in from southern and
central NSW. The Victorian Department of Environment and Primary Industries (DEPI) team have
been testing canola samples for BWYV. So far 180 crop samples have been submitted for virus
testing and 940 plants have been tested for BWYV.
The overall result for BWYV testing is 75 % of plant samples were positive for BWYV. The incidence
of BWYV in plant samples from crops tested by state is –
SA 85 % infection,
Vic 59 % infection and
NSW 48 % infection (limited samples from Mildura, Robinvale and Swan Hill).
Some crops in the lower north region of SA have been badly damaged, having been infected at the
highly susceptible rosette stage. The majority of canola crops appear to have been infected at a
slightly later growth stage and while they may suffer yield loss, these losses will be less than in the
early affected crops. If infection does not occur until mid podding then minimal yield loss will
eventuate, although oil quality may be compromised.
Many canola crops show widespread virus infection and it is questionable whether insecticides are
warranted in these cases unless aphids are causing direct feeding damage. If crops show patchy
infection it may be necessary to control the aphids to prevent further spread of aphids and virus
during late winter and spring.
Pulse crops (lentil, faba bean, chickpea and field pea) are susceptible to BWYV and the GPA in canola
may transfer this virus to nearby pulses. Once established in a few plants further spread may occur
via cowpea aphid although at a much lower transmission rate than via GPA. It may be necessary to
control aphids in these crops and in adjacent canola crops to reduce virus damage in pulses.
Where insecticide sprays are considered necessary, aphids should be monitored via sticky traps in
canola and pulse crops to determine the correct timing of the sprays. Only insecticides registered for
the crop and situation should be used. Specific information on insecticides and trapping aphids will
be available in the next issue of Pest Facts.
BWYV and GPA Information days– open invitation to agronomists and growers:
Jenny Davidson and Greg Baker will speak about GPA and BWYV at
Cummins Bowling Club 11.00 am Tuesday 29th July
Kadina Farm Shed 10.30 am Wednesday 30th July
Jenny and Greg have already spoken at Hart winter walk (Tuesday 22nd July), Tarlee High Rainfall
Zone winter walk (Wednesday 23rd July) and Crop Science Society (Wednesday 23rd July).
Ascochyta blight in Farah and PBA Rana faba beans
Ascochyta leaf spot has observed at high levels in many crops, a result of spread during recent rains.
Some crops of PRB Rana and Farah are also affected in the lower and mid-north of SA where a new
virulent strain of the fungus has been identified. In these regions, cv. Farah should now be
considered susceptible to the disease, comparable to cv. Fiesta, and managed accordingly. Early
fungicide sprays ahead of rain events during late July and early August will be critical to slow the
development of the disease and reduce yield loss.
Chocolate spot in faba beans
Early infection of chocolate spot has also been identified in faba bean crops on the Eyre Peninsula
and mid-north of SA. While this disease will be slow to develop during cold conditions, rapid spread
is expected as temperatures rise (above approx. 170C). Fungicide sprays applied before canopy
closure during late July and early August will be critical to slow the development of the disease and
ensure protection of flowers, which are particularly sensitive to infection. This disease will thrive in
crops with dense canopies and wet soils and can spread rapidly if unprotected.