Aarhus, Denmark
February 21, 2013
Scientists and technicians at Aarhus University’s Research Centre Flakkebjerg are investigating if fungicide resistance is developing to the plant pathogen Septoria, which causes significant losses in wheat. A major group of fungicides currently used are in some parts of Europe seen to lose some of their potency.
Septoria is a fungal disease which can attack wheat and cause severe yield losses. It is therefore one of the plant diseases that scientists at Aarhus University’s Research Centre Flakkebjerg are keeping a watchful eye on. Not least because some of the fungicides currently used appear to become less effective over time.
The important top leaves
Septoria starts at the bottom of the wheat plant and moves upwards, typically by fungal spores being spread from leaf to leaf by raindrops. After four to five days with rainfall, the risk of an attack affecting yields is regarded so significant that it becomes necessary to spray against Septoria. A crucial factor in the minimisation of yield losses from disease attack is that the two upper leaves are kept disease-free until the end of the grain-filling period.
- Data show that up to 70 percent of the grain yield in wheat is due to the photosynthetic activity in the two uppermost leaves, explains Lise Nistrup Jørgensen from Aarhus University.
In most growing seasons, one or two fungicidal fungicide treatments will typically be carried out to minimise Septoria attacks. If you do not control the fungus, it can cause yield losses of typically 1−1.5 tonnes per hectare if the top leaves are severely infected. Septoria is seen as the most important disease in wheat since it is found to be present every year to a greater or lesser degree, explains Lise Nistrup Jørgensen.
Disease tested in the laboratory
An important task in connection with the control of Septoria is to ensure and check that the fungicides applied are still effective. Each growing season therefore involves the collection of leaves infected by Septoria from samples coming from all over the country. In the laboratory the fungus is isolated from the leaves and tested against different concentrations of individual fungicides.
- This provides knowledge on whether the sensitivity has changed and provide information on wether we should change our control strategy or use other fungicide groups to obtain an adequate control of Septoria, says Lise Nistrup Jørgensen.
- We are part of a European network that carries out sensitivity analyses for different fungi. Fungi know no boundaries or national borders, so we have seen examples of resistance developing in, for example, Germany which have then later appeared in Denmark, explains Lise Nistrup Jørgensen.
Sensitivity is wearing off
Data from neighbouring countries indicate that the effect from treating Septoria with triazoles – the fungicides most commonly used in cereals – is weakening.
- This is worrying since we have no strong alternative fungicides in Denmark that would be able to replace these fungicides. It is therefore important that we closely follow the development in Denmark, says Lise Nistrup Jørgensen.
So far the triazoles still provides effective control in Danish fields. However she points out that there are several examples where fungicides have caused rapid development of resistance, which meant they could no longer be used for control of Septoria. So we need indeed to follow, how the sensitivity develops in the future.
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