As rain continues to fall and the days get longer and warmer, the crop disease risk is heightened.
However, enacting disease management strategies is proving challenging for Wimmera and Mallee farmers with monitoring and spraying activities hampered by wet and muddy conditions and stories of bogged sprayers not uncommon over recent weeks.
Barley leaf rust has been identified in parts of the medium to low rainfall zone, with compass barley (rated very susceptible to leaf rust) particularly showing symptoms of the disease.
In high disease level years, yield losses from leaf rust can be up to 30 to 40 per cent, however there are conflicting opinions on how to best manage it.
At BCG’s Main Field Day last month, Swan Hill-based agronomist Rob Sonogan said this was because there was very little research about how to deal with leaf rust in medium to low rainfall areas.
“Target your malting varieties as a first priority, to try and get the quality,” he said.
“With late sown crops, which are in early head emergence, it’s probably okay to aerial spray, but it’s not as effective as ground spraying.”
To manage disease effectively growers should understand the disease ratings of their varieties especially when considering any adult plant resistance (APR) which can be hindered in cooler conditions.
Wheat crops are also at risk of disease this year with specific cases of stripe rust identified at Nullawil and Rupanyup last week, and reports that the disease is now widespread.
Stripe rust can cause large losses depending on the susceptibility and growth stage of the plant; up to 75 per cent for susceptible varieties at growth stage 39 (flag leaf emerged) down to zero per cent for resistant varieties at growth stage 65 (mid flowering).
Farmers are being urged to identify any infestation of stripe rust as soon as possible and treat accordingly.
The best time to identify stripe rust is in the early mornings, paying particular attention to the older leaves. It is the yellow stripes of pustules raised above the leaf surface that farmers need to be looking for.
Prioritising cost effective outcomes for spraying is necessary, as many paddocks will be too wet to access and yield and quality should be maintained.
Malting barley should be monitored closely as disease issues at this stage in the season can cause serious quality issues.
When applying fungicide farmers need to remember that treatments will only benefit undamaged leaf area, therefore considering the importance of the leaf and the area affected will help determine the priority of the crop to be treated.
Fungicide treatments for rust is an area in which BCG is undertaking field trials to ensure accurate and up-to-date information. Particular interest is to the effectiveness of sprays at different growth stages, with ten different fungicide treatments currently being trialed with the results to be released after harvest.
For details contact BCG on 5492 2787 or log on at www.bcg.org.au.
This article was published in the Stock & Land on October 6, 2016.
