CropAlert Crop Diseases August 2011

CropAlert Crop Diseases August 2011

Wheat rusts Victorian wheat crops are currently exposed to unprecedented rust pressure. This has resulted from two consecutive wet summers that have enabled rust levels to build up over the past two years.

Inspections of crops and trials across western Victoria have confirmed the need for growers to be proactive in their rust management.

Stripe rust is appearing in crops about 3 to 4 weeks earlier than normal. It is widespread across Victoria and hot spots are becoming evident in Wimmera crops. The earlier that rust appears in a crop the greater the damage if it is not controlled.

Leaf rust is widespread in susceptible varieties in the Mallee. This is unusually early for this disease to occur in Victoria and it will become more important as the weather warms during spring. Growers need to plan to manage this disease in susceptible varieties.

Observations of stem rust in Yitpi crops in the Mallee provide another warning of the potential risk from this disease in unprotected susceptible crops. Without effective management, stem rust will be explosive in susceptible crops when the weather warms to its ideal temperature (15-30° C) in the late spring. Now is the time for growers to implement their stem rust management plan.

In light of these early rust reports and the potential damage to crops it is important that growers take the following action:

  1. Review the resistance ratings of cultivars to the three rusts in the Cereal Disease Guide 2011.
  2. Monitor all wheat crops weekly for early signs of rust (including resistant crops in case of a change in the pathogen, and there is “resistance breakdown”).
  3. Revise rust management strategies for the remainder of the season and consider: Fungicide applications at both full flag leaf emergence (GS39) and again a full ear emergence (GS59) for effective rust control. Since stem rust continues into warmer temperature it will be necessary to apply fungicides post ear emergence in susceptible varieties. That foliar fungicides will provide the best control when used proactively instead of reactively. That is, apply fungicides to the crop before the disease takes hold. That this year it is likely that earlier and/or more fungicide sprays will be required.
Barley diseases

Scald, the spot form of net blotch (SFNB) and leaf rust will need to be managed during 2011. Scald symptoms are starting to appear in susceptible barley varieties, and will continue to develop and become severe with the onset of warmer weather. Control scald early using foliar fungicide application between GS31 (stem elongation) and GS39 (flag emergence). A second application may be necessary where symptoms persist past GS39. Spot form of net blotch is also widespread within crops of Gairdner and Hindmarsh showing symptoms on the lower leaves of seedlings. SFNB can be suppressed using foliar fungicide application between GS31 and GS39. Barley leaf rust is present throughout the Victorian barley growing regions and will develop into an epidemic in the Wimmera and Western districts if favourable weather conditions persist into spring. Application of foliar fungicide will reduce inoculum levels and provide several weeks of protection.

Pulse diseases

Ascochyta and Botrytis grey mould will need to be managed in most chickpea and lentil crops in 2011. Chickpeas: The season has been favourable for the development of Ascochyta blight, and it is recommended that chickpea crops be actively monitored. Early infections have been detected on the variety Slasher. Varieties with low resistance like Howzat will need to be closely monitored and sprays to control Ascochyta may be necessary. Botrytis grey mould is also likely to become an issue if seasonal conditions continue to favour this disease.


Ascochyta blight has been detected in the variety Flash. The canopies of many early sown lentil crops have started to close or have already closed. It is imperative that fungicides are applied before canopy closure to manage Botrytis grey mould.

Faba beans

Rust, chocolate spot, Ascochyta and Cercospora have been detected early this season. Early spraying of fungicides is warranted as these diseases can develop rapidly. Experience suggests that late sprays are not as effective. Rust in particular can develop rapidly when temperatures are over 20° C, cycling every 10 days. Correct disease identification of faba bean diseases is important as fungicides can be disease specific.


Even though reports of viruses in pulses crops have been low so far this season, favourable spring conditions will see a build-up of aphids, and the potential for spread of associated viruses. Growers should be on the lookout for aphids, as we move into spring. Spraying with insecticides may be necessary in some situations.

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