Septoria
Septoria is the biggest yield-robbing foliar disease of winter wheat. In this Academy module, Rothamsted Research's John Lucas explains why it is so prevalent.
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What is septoria?
Septoria leaf blotch is the UK's most important foliar disease of winter wheat. Caused by a fungus, Mycosphaerella graminicola, it is better known as Septoria tritici.
Oblong patches of dead tissue develop on leaves containing numerous small black structures.
In severe outbreaks these lesions may coalesce so the whole leaf becomes yellow-brown and desiccated.
Epidemics start during autumn and early winter with the arrival of airborne ascospores, released from sexual fruit bodies (ascocarps) on the remains of previous crops.
Ascospores infect emerging leaves of wheat seedlings to cause the first disease lesions.
Within these lesions the fungus forms small, black, flask-shaped structures called pycnidia.
These produce needle-shaped asexual spores (pycnidiospores) that ooze out on to the leaf surface during wet weather.
Rain-splash then spreads the spores to higher leaves as they emerge, where they infect and initiate further lesions containing pycnidia. Several cycles of infection can, therefore, take place, with the disease spreading up the plant.
Later in the season the sexual ascocarps are formed in dead tissue, and these persist on crop debris to initiate disease on the following crop.
The impact
Septoria depresses crop yield by reducing green leaf area and the capacity of the crop to produce sugars through photosynthesis.
This is particularly damaging if the disease reaches the top three leaves, which contribute most to grain filling and yield.
If not controlled, septoria can routinely reduce yields by 1-2t/ha and on susceptible varieties in severe disease seasons the impact
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