Tillage after Chlorothalonil - The loss of 'Bravo' will present big challenges for cereal growers

The EU Commission has voted to ban chlorothalonil. File photo
The EU Commission has voted to ban chlorothalonil. File photo

Ciaran Collins

The European Standing Committee on Plants, Animals, Food and Feed (SCoPAFF) has voted against renewal of approval of the fungicide Chlorothalonil.

No dates are confirmed but it will be available for this season. Chlorothalonil (often referred to as Bravo) is a key active ingredient for the control of ramularia in barley and it is an important part of an anti-resistance strategy in wheat.

Teagasc produced a report last autumn on the possible implications of the loss of chlorothalonil. One of the key points was that where chlorothalonil is not available the report estimates the most likely scenario for e-Profit Monitor farmers is an average Net Margin reduction of over 50pc in wheat and 65pc in barley.

The report also states that in the medium term the introduction of new fungicides will be welcome and will increase disease control options. However, in the absence of chlorothalonil, a more rapid loss of efficacy of these fungicides is expected due to high disease pressure.

Ramularia Ramularia has appeared in winter barley crops earlier than expected this season and it is vital that chlorothalonil is used in the programme as other fungicides cannot be relied on for control.

Typical symptoms of ramularia are small brown rectangular lesions surrounded by a yellow halo.

One of the distinguishing features of ramularia is that it can be seen through the leaf. Sometimes symptoms can be seen on lower dead leaves but normally symptoms appear post flowering.

Crop stress caused by drought, water logging or flowering are potential triggers. It has the potential to cause significant reductions in yield.

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While differences do appear between varieties in terms of their ability to resist the disease in high pressure environments often experienced in Irish crops, these differences will be small and as such it is advised that fungicides are applied for its control.

In recent years there have been reports of SDHI and azole fungicide resistance occurring in European Ramularia populations. To date limited information is available on the Irish population, but given the biology of the pathogen it must be assumed that resistance is present in the Irish population.

As such both the SDHIs and azole fungicides should not be relied on for the control of ramularia.

Resistance in ramularia to the strobilurins is now widespread.

Chlorothalonil still remains very effective in the control of ramularia and it is strongly advised that it is applied at the final fungicide timing. It may also be considered at an earlier timing if symptoms are present in the crop. It is vitally important that chlorothalonil is applied prior to the development of the symptoms and there may be a requirement to use it earlier in the winter barley programme than the traditional final timing.

Ciaran Collins is a Teagasc crop specialist based in Moorepark, Co Cork

Indo Farming