QiI Fungicides
Introduction and General Information
QiI fungicides (FRAC Group 21) inhibit mitochondrial respiration by binding to the Qi site (C4) of the cytochrome bc₁ complex. While sharing the same mode of action, QiI compounds differ markedly in their disease and crop spectra. Amisulbrom and cyazofamid target oomycete pathogens such as late blight and downy mildews, whereas fenpicoxamid and florylpicoxamid are active against ascomycete and basidiomycete fungi and show no activity on oomycetes. These distinct profiles require separate resistance-management approaches within FRAC Group 21.
| Code | Target site and code | Group name | Disease spectrum | Chemical group | Common name(s) | Comments |
| 21 | C4 Quinone ‘inside’ (Qi) binding site of the cytochrome bc1 (ubiquinone reductase) |
QiI fungicides (Quinone inside Inhibitors) |
Oomycete | Cyanoimidazole | Cyazofamid | Medium to high risk Picolinamides show no spectrum overlap with Oomycete compounds amisulbrom and cyazofamid. See FRAC Qil Guidelines for resistance management. |
| Oomycete | Sulfonamide | Amisulbrom | ||||
| Non Oomycete Actinomycete Basidiomycete |
Picolinamides | Fenpicoxamid Florylpicoxamid |
Monitoring Results and Recommendations
At the annual meeting, the working group reviews the current year's monitoring results and decides whether they require changes be made to the next year's use recommendations. The minutes of those meetings are below.