Recent wet conditions have been ideal for disease development in Victoria. Diseases will be best controlled using a proactive fungicide response before disease has fully developed. It is not the year to wait and see!
Stripe rust, powdery mildew, septoria and yellow leaf spot are present in wheat crops. In barley, spot form of net blotch (SFNB) is widespread and scald is starting to appear.
Powdery mildew in wheat
Powdery mildew is appearing in Wimmera and Mallee wheat crops, especially cv. Scepter, which is rated as SVS. Ideally this disease is controlled with a spray prior to canopy closure (~GS31), however, a spray even at full flag emergence (GS39) will still be useful and also provide protection for rust later in the season. For more information refer to the GRDC information note ‘Powdery mildew in barley and wheat’.
Septoria in wheat
Septoria is widespread in Victorian wheat crops. In the Wimmera, a spray at early tillering is recommended if Septoria symptoms are present in the crop. In the Mallee, Septoria should be considered as part of the stripe rust and mildew control strategy. In the high rainfall zone, susceptible varieties must be protected with fungicides. Inspect crops carefully, focusing on the oldest leaves looking for lesions with black fruiting bodies present. Applying fungicides early in the epidemic will provide more effective control than letting the disease develop.
To help protect fungicides from resistance developing, the same active should not be applied more than once in any crop. Ideally different fungicide groups should be applied and mixtures used. For more information refer to the ExtensionAUS™ article ‘Protect wheat from Septoria tritici this spring’.
Stripe rust in wheat
Stripe rust is present in the Victorian Mallee and is expected to spread quickly during September. As this is a relatively early outbreak of stripe rust, it is recommended that all wheat crops rated as MS or worse are protected with a fungicide at ~GS39 and then monitored for further rust development. Consult the Agriculture Victoria current disease guide for variety ratings.
Scald in barley
As expected, scald is starting to develop in barley crops. It is important that once scald starts to develop that a fungicide is applied soon after its detection. Agriculture Victoria research has shown that good scald control can be achieved by applying fungicides at both GS 31 and 39, or if an up-front treatment has been used (e.g. flutriafol or Systiva) a fungicide application at GS 39 provides good control. A proactive approach to scald control in susceptible varieties is warranted in Wimmera and high rainfall zone crops.
SFNB partial resistance to Systiva
There is a confirmed report of partial resistance to Systiva in SA (SARDI and CCDM). Agriculture Victoria has sent multiple samples to CCDM for testing and we will provide an update when results become available. At this stage, our recommendation is that this finding will not change the recommendation to apply a spray at GS39, given the pressure from recent conditions. Agriculture Victoria has shown that good control of SFNB can be achieved by applying foliar fungicides at both GS 31 and 39, or if Systiva was used then at GS 39.
This article was originally published as an Agriculture Victoria CropSafe Crop Alert supported by the GRDC.