Investigating the effectiveness of the Thies Clima “Septoria Timer” to schedule fungicide applications to control Mycosphaerella graminicola on winter wheat in Ireland

The effectiveness of an in-crop decision support system, the Thies Clima “Septoria Timer”, to schedule fungicide applications for the control of Mycosphaerella graminicola in winter wheat was evaluated over five seasons, 2001–2005. Spray applications, based on the output from this instrument, were compared with routine two-spray fungicide programmes applied at growth stages 37 and 65, or three-spray programmes applied at growth stages 32, 39 and 65. Septoria infection periods, as defined by the “Septoria Timer”, varied from 12 in the 2002 season to two in 2004. There were 12 spray applications based on output from the “Septoria Timer” over the 5-year period compared with 15 for the standard three-spray programme and six for the standard two-spray programme included in 2003–2005). Over the same period, there was a corresponding reduction of 41% in the load of active ingredient entering the environment. Pycnidia of M. graminicola were counted on infected leaves in 2002 and 2003. Scheduling fungicide applications according to the “Septoria Timer” significantly reduced the number of pycnidia on the flag leaf compared with a three-spray programme in 2002, but there was no effect in 2003. There were no significant differences in values for the flag leaf area under the disease progress curve (AUDPC) between the three fungicide scheduling protocols in 2002 and 2005. Also, there was no significant difference in AUDPC values between the “Septoria Timer” and the three-spray programme in 2003 and 2004. All fungicide programmes significantly increased grain yield each season. In 2001, applying fungicides scheduled by the “Septoria Timer” protocol resulted in significantly lower yield compared with fungicide applications scheduled by crop growth stage. There was no significant yield difference between the three fungicide scheduling protocols in 2002 and 2004. In 2003 and 2005, there was no significant yield difference between fungicide programmes guided by the “Septoria Timer” output and the standard three-spray programme. Grain-specific weight in all seasons, with the exception of 2004, was significantly enhanced by fungicide application compared with the untreated control. During 2001–2005, scheduling fungicides according to the “Septoria Timer” provided grain of similar quality to that from plots receiving the three-spray standard programme.