Stubble borne diseases

Wimmera and Mallee farmers have been fortunate this season to be reaping the rewards of high yielding crops. Subsequently, many growers will be leaving large stubble loads behind in pursuit of a faster harvest.

Farming systems have also changed meaning more stubble is retained for environmental and soil health reasons, so understanding the role stubble plays in providing disease habitats is important.

Growers need to consider the risks with regards to stubble borne diseases following a year of high disease burden.

Many diseases that affected large parts of the Wimmera and Mallee in 2016 are able to survive the summer period on stubble, therefore providing the perfect opportunity to infect 2017 crops as soon as conditions are conducive.

When it comes to many stubble borne diseases, subsequent planting of the same species into infected paddocks results in a higher risk of large yield losses and plant health issues.

Scald has shown significant issues in barley in the past due to the planting of susceptible varieties into infected stubble.

Rotation is a practice that is vital to disease management, and especially prevalent for stubble borne disease management.

By rotating species you reduce the availability of infected material, thus reducing the amount of disease in the paddock that can infect future crops.

The longer the disease does not have plant material it can infect, the better it is for the grower as the inoculum available will reduced. 

Blackleg infection in canola can cause significant issues for subsequent plantings even in different paddocks as the spores become airborne and can travel large distances.

A BCG research trial in 2011 found that a buffer of 500 metres between canola stubble and the next seasons plantings is ideal to reduce the risk of infection. 

If planting a different species is not an option in 2017, planting varieties that have a high resistance rating will be important.

Understanding the disease susceptibility and resistance ratings (and tolerance in pulses) of varieties will be of great importance in 2017. Resistance ratings will assist in mitigating the risks associated with stubble borne diseases.

As a result of the significant disease pressure placed on varieties in 2016, stay informed and ensure you understand any changes in the current ratings.

There are many other diseases that persist on stubble including rust, yellow leaf spot, septoria tritici blotch, net form of net blotch, spot form of net blotch, blackleg, ascochyta, chocolate spot, botrytis grey mould and crown rot.

Ensuring that you are aware of the prevalence of these diseases in your paddocks and understanding the risks associated for future seasons will give you an opportunity to better plan species and varieties for 2017.

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