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Septoria Tritici
Mycosphaerella graminicola
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General Description
Septoria tritici is currently the major disease in wheat. Although more resistant varieties, including Robigus have recently been added to the HGCA Recommended List, many varieties remain susceptible, including Consort. Issues concerning fungicide resistance have made it more of a challenge to manage in susceptible varieties.
Septoria tritici can occur at any time during the growing season. It causes the most damage to yield if it attacks the upper leaves, in particular the flag leaf.
Biology
Weather conditions which suit the spread of Septoria tritici spores from the bottom of the crop to the upper leaves are wet and windy. Spores ooze from affected lower leaves and are spalshed up the plant in heavy rain. Dew and wind can also chieve the same effect. Crop canopy can play a role in spreading the disease. Short crops or crops wehre leaf layers overlap make it easier for the disease to spread.
Wet or windy weather conditions at flag leaf emergence are therefore high risk for disease spread.
Advice
Select varieties with better resistance to Septoria tritic, including Robigus.
The key fungicide groups to control the disease include triazole fungidies, e.g. Opus and Proline and chlorothalonil fungicides e.g. Bravo.
Diary
April
Stem Extension Treatments Due This Month
The stem extension treatments are key to protecting the crop from the stem base disease common eyespot, and the key foliar diseases Septoria tritici, powdery mildew and yellow rust. More...
May
Fungicides at flag leaf emergence
Keeping the top leaves free from disease is important in winter wheat. More...
Resistance Issues
Resistance to QoI (Strobilurin) fungicides is now widespread in the UK, and in 2005 expect 80-100% resistance. As such, they should not be relied upon for disease control. They do add to the control of the disease and to yield when used in a mixture with a triazole fungicide however.
There are also issues with resistance to the triaozle fungicides. This type of resistance is more subtle. Where a half dose of Opus may have given 90% control 10 years ago, you can now expect this to have fallen to approximately 60% control. It is not clear if the decline in control will continue, or flatten out to a level where the fungicides remain active.
There are no resistance issues concerning the multisite fungicide chlorothalonil.
Forecasting
Use this section to help manage the disease through the season.