Key points
- Winter wheat fungicide programme trials were set up in the 2014-15 season in the Manawatu (dryland), Central Canterbury (irrigated) and South Canterbury (dryland).
- The yield response to fungicide ranged from nil in the South Canterbury trial to more than double in the Manawatu trial. The margin over fungicide cost ranged from a loss in the South Canterbury trial to over $1,800/ha in the Manawatu trial.
- The three SDHI fungicides Adexar®, Seguris Flexi® and Aviator Xpro® performed strongly against Septoria tritici blotch (STB) at the label rate and at a 20% to 30% reduced rate (each treatment had 75% triazole co-formulated with the product or added to the mix).
- Comparing different three spray programmes there was an indication that better STB control was gained with two SDHI + triazole sprays timed at GS32 and GS39 compared with either one SDHI + triazole spray at GS39 or two sprays at GS39 and GS65 but this was not reflected in the yield of the Central
- A Timing 0 (T0) at GS30-31 spray (1.0 l/ha Opus) in addition to a three spray programme did not give a significant yield increase in any of the trials. However, the 0.5 t/ha yield increase (not significant) in the early sown, high yielding Central Canterbury crop of cultivar Wakanui is similar to previous trial results in irrigated, early autumn sown wheat.
- For a dryland crop with low STB disease pressure and a moderately resistant cultivar, eg. South Canterbury trial, the fungicide programme may not always prove cost effective but can be minimised e.g. triazole at GS32, SDHI with 75% triazole at GS39 and optional spray at GS65 depending on dryness.
- The wheat crop in the Manawatu trial became infected with Fusarium head blight. The crop followed maize where it is common for the maize residue to harbour Fusarium. So it is difficult to determine yield contribution from STB control versus Fusarium effects.