This Update outlines the latest results on how Zymoseptoria tritici (Zt), the fungus that causes Septoria tritici blotch (STB), is responding to triazole fungicides in New Zealand wheat crops.
Key Points:
- Zymoseptoria tritici (Zt), the cause of Septoria tritici blotch (STB), is showing reduced sensitivity to triazole fungicides in New Zealand.
- Prothioconazole-desthio and epoxiconazole are less sensitive in lab tests, while mefenitrifluconazole remains more sensitive.
- New genetic types of Zt (haplotypes) linked to reduced sensitivity have been detected, especially in South Otago/Southland.
- Regional differences in sensitivity are emerging, but triazoles are still performing in the field.
- Careful stewardship, i.e. mixing, rotating, and limiting triazole sprays, is essential to protect their ongoing usefulness.