Stripe rust hot spots were this week (September 11 2014) discovered near Beulah.
In light of this discovery, growers are urged to check their crops and to make a plan now.
A fungicide application is advisable for those growing Mace (which most would have already done) or other varieties susceptible to stripe rust (such as Derrimut or Corack). However, in the Mallee at this stage in the season, varieties with adult plant resistance are unlikely to benefit from a fungicide spray, nor will any varieties that are already out in head. Mace does not have adult plant resistance and will need to be monitored closely, even after head emergence.
Wimmera growers should check all their crops and make a decision now. If you detect rust or think a fungicide spray is warranted, do so without delay. The benefits of a fungicide application will only be realised if timely spraying occurs, so if you do decide spraying is not warranted, make the decision and walk away. Deciding to spray two weeks later is likely to be a futile exercise.
This year in particular, it is pertinent to consider yield potential before deciding to spray. Remember, a fungicide will only benefit undamaged leaf area. If a lot of leaf area has been lost to moisture stress, frost or disease, or if you think your yield potential is below 1.5t/ha, it may not be economically beneficial to spray.
Unlike leaf and stem rust, stripe rust spores do not require free water to germinate. They can germinate in as little as six to eight hours at temperatures between five and 15°C. In winter, spores tend to clump together (giving rise to ‘hot spots’) while in spring, spores tend to disperse singly, causing a more uniform infection.
Stripe rust is easiest to detect in the morning and is identifiable by the appearance of yellow stripes of pustules, particularly on the older leaves. These pustules are raised above the leaf surface and can be easily wiped off. If there is a morning due, detection can be more difficult and growers may need to look at the underside of the leaves, especially the flag minus one.
Hot spots can be one to 10 metres in diameter and are generally well developed just before the disease becomes widespread in the crop.
Growers concerned about stripe rust can phone BCG on (03) 5492 2787. More information on stripe rust management was published in the 2005 BCG Season Research Results.
