Teagasc tillage specialists are confirming that the loss of chlorothalonil will force Irish wheat growers to amend their septoria control spray programmes this year and into the future.
However, the coming on stream of new chemistries to manage the disease gives hope that the effective control of the disease remains in the hands of farmers.
Timing of spray applications has already been highlighted by Teagasc agronomists as being of critical importance when it comes to dealing with disease in cereal crops.
Septoria control at growth stages
The three-leaf and full flag leaf emergence stages are viewed as being critical in this regard; the days of spraying by calendar date are over.
Making decisions on future fungicide applications will be controlled by the growth stage of the crop and the level of disease that has been identified.
Trials have confirmed that there is little benefit in treating wheat crops for septoria until the third leaf has fully emerged and/or after the flag leaf has emerged.
Alternatives to chlorothalonil
With the loss of chlorothalonil, Teagasc is now recommending the use of multi-site Folpet to reduce disease resistance and septoria control.
Two applications are recommended, each at a rate of 1.5L/ha. The first should be applied at the three-leaf stage, the second when the flag leaf is fully emerged.
The effective use of a fungicide at flag leaf stage can deliver yield increases of up to 1.7t/ha.
Teagasc advisors are also pointing out that there is little opportunity to reduce fungicide application rates in years when a high disease pressure exists.
Winter barley
Turing to winter barley, Teagasc advisors are confirming that crops are now at growth stage 30.
Septoria nodorium and rhynchosporium are the main disease threats in barley at this time of the year.
Teagasc trials have confirmed that the best control response to these diseases can be secured at the stem extension stage with a follow-up programme at awn emergence.
Earlier fungicide treatments can be justified if disease levels in crops are high at the late tillering stage.
Fungicide programme
The first port of call in drawing up a fungicide programme for winter barley is to examine the recommended list and take note of the disease resistance associated with the crops being grown.
Crops should then be walked in order to identify the actual disease threats that exist in the field. Fungicide programmes can then be designed on the back of this information.
Teagasc trials have shown that there is no benefit to using more than half rates of the various fungicides in the various tank mixes used.
Chlorothalonil will be missed in terms of its ability to control ramularia later in the season. Given this scenario, Teagasc is advising an application of 1.5L/ha of Folpet at awn emergence.