This Update outlines the latest results on how Zymoseptoria tritici (Zt), the fungus that causes Septoria tritici blotch (STB), is responding to succinate dehydrogenase inhibitor (SDHI - Group 3) fungicides in New Zealand wheat crops.
Key Points:
- Zymoseptoria tritici (Zt), the cause of Septoria tritici blotch (STB), is showing a gradual reduction in sensitivity to SDHI fungicides in New Zealand.
- New genetic variants of Zt linked to reduced sensitivity have been detected, especially in Canterbury, but are not yet widespread.
- The diversity of Zt variants and combinations of variants is likely to increase, which will impact on field performance.
- Regional differences in sensitivity are emerging, but SDHIs are still performing in the field.
- Careful stewardship, i.e. mixing, rotating and limiting the number of SDHI sprays is essential to protect their ongoing usefulness.
Related updates:
Cereals Update 232: Managing Septoria: Latest results on triazole performance
Cereals Update 233: Managing triazoles for prolonged performance in autumn sown wheat