Key Points
- Strobilurin use should be limited no more than two applications per season in wheat crops to minimize the potential impact of resistant mildew populations.
- Two spray ‘straddle’ programmes (strobilurin/Opus mixtures at GS33 & 55) have given margins equal to, or better than, 3 spray strobilurin programmes in Mid Canterbury over 6 years.
- However 0.25l/ha Opus at GS30/31 should precede this straddle programme if early stripe rust infection (or in South Canterbury/Southland Septoria) is noted at early stem elongation.
- The new triazole Proline (prothioconazole) was inferior to Opus where leaf rust was present; however a Proline/fluoxastrobin mix (to be branded as the product Fandango) was equal to Opus/Comet.
- In South Canterbury, with longer grain fill periods and early Septoria infection, a 3 spray programme (Proline 0.4 at GS32 and GS39 and Opus 0.25 + Amistar 0.25 at GS65) was slightly more cost effective than the straddle programme preceded by Opus 0.25 at GS30. However, both were superior in margin to the 3 spray strobilurin programmes.
- Adding strobilurin to Opus at GS32 and 39 improved the margin ($) in irrigated but not in dryland crops.