Australia
October 9, 2007
Source:
GRDC's The Crop Doctor
Recent rainfall and temperature
conditions in Western Australia, leading to increased stripe
rust in wheat, highlight the need for growers to sow rust
resistant varieties, be vigilant for signs of an outbreak and
time fungicide applications for maximum results.
Optimal day temperatures for stripe rust development are 7-15 OC
and usually occur in winter.
Dr Rob Loughman, Principal Plant Pathologist at the
Department of Agriculture
and Food Western Australia (DAFWA), emphasises susceptible
crops that have not received prior fungicide protection are at
greatest risk of stripe rust, particularly in districts already
reporting outbreaks this season.
Because of staggered crop sowings, stripe rust development this
year is a greater risk in later sown crops, as these are
developing when more stripe rust is present. Of existing crops,
those behind in development will be at higher risk than those
flowering, as the disease has more time to develop.
Susceptible crops require protection as soon as stripe rust is
detected, provided this is before flowering.
Crops developing under cool conditions, or those in cooler
southern wheat growing areas, are likely to be more prone to the
disease.
Stripe rust typically slows as temperatures rise in spring,
which occurs earlier in central and more northern agricultural
areas than in southern areas.
By mid-September, stripe rust had spread primarily in a
southerly and western direction, from the first recording in
mid-August, south of Cunderdin.
Until mid-September, progression in the central wheatbelt was
slow, with agronomists and growers quick to detect and control
new outbreaks with fungicide and preventing build-up of inoculum
on susceptible wheat varieties.
According to Dr Loughman, new strains of stripe rust can evolve
faster if rust is allowed to develop on susceptible wheat
varieties.
Discriminating between different fungicides is considered less
important than timing, or rate, when it comes to control.
In the lead-up to harvest, Dr Loughman reminds growers that the
best way to reduce losses from rust is to adopt an integrated
approach. This involves selecting the most resistant varieties
for specific agronomic conditions, reducing over-summering
susceptible volunteers and closely monitoring crops and disease
pressure to maximise the efficacy of foliar treatments.
Growers wanting more information should visit the GRDC website
www.grdc.com.au/rustlinks and PestFax at www.agric.wa.gov.au
for the Rust Report.
Also available from DAFWA’s website is a Farmnote: ‘Managing
stripe rust and leaf rust of wheat’. |
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The Crop Doctor is
GRDC Managing Director,
Peter Reading |
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