Quinone outside inhibitor fungicides are synthetic derivatives of naturally occurring strobillurin compounds introduced in the late 1990s and represent a novel group of fungicides, highly active against a broad range of fungi belonging to Oomycetes, Ascomycetes, Basidiomycetes and Deuteromycetes. They are mitochondrial respiration inhibitors (MRI) which inhibit fungal respiration at the Quinone “Outside” (Qo) binding site of the cytochrome bc 1 complex. Being site-specific, they are at risk from the development of resistance in the target plant pathogens.
QoIs are not cross resistant with other fungicide groups, but there is a cross resistance among all active ingredients within QoI group which includes azoxystrobin, kresoxim-methyl, demoxystrobin, fluoxastrobin, metaminostrobin, orysastrobin, picostrobin, pyraclostrobin, trifloxystrobin, and the non-strobilurins, famoxadone (oxazoldinone compound/oxazole fungicide) and fenamidone (imadizilinone compound/imadizole fungicide). QoI group of fungicides were previously known as STAR (Strobilurin-Type Action and Resistance/ Strobilurins And Related compounds) fungicide.In order to minimize the likelihood of resistance development, resistance guidelines provided by FRAC must be followed, which involves following key points:
• In cereal crops the number of QoI containing sprays must not exceed two.
• QoI products must always be used in combination with a product, other than QoI, recommended for the control of same disease.
• QoI product should be used preventively or as early as possible in the disease cycles keeping aside reliance on curative ability.
It is therefore vitally important that all users of QoI fungicides adhere to the latest resistance management guidelines for cereal and other crops available from FRAC. For latest updates, consult the web page, http://www.frac.info/.
Some solo and coordinated products commercially developed for various QoI fungicides are given below:
Commercially available QoI fungicides
| Company / Common Name | Solo Product | Coordinated Products |
| Syngenta Azoxystrobin | Abound, Amistar, Heritage, Quadris | Uniform (azoxystrobin + mefanoxam) Quilt (azoxystrobin + propiconazole) Quadris Opti (azoxystrobin + chlorothalonil) |
| Du Pont Famaxadone | Famoxate | Tanos 50 DS (famaxadone + cymoxanil) |
| Bayer CropScience Fenamidone | Reason, Fenstar Fenomen, Sonata, Sereno | |
| Arysta LifeScience Fluoxastrobin | Disarm, Evita | |
| Bayer Fluoxastrobin | Vigold | |
| BASF Kresoxim-methyl | Sygnus, Sovran, Stroby | Collis (kresoxim-methyl + boscalid) Allergo (kresoxym-methyl + epoxiconazole) |
| Bayer CropScience Metaminostrobin | Oribright1 | |
| BASF Orysastrobin | Arashi2 | |
| Du Pont Picoxystrobin | Acanto | |
| BASF Pyraclostrobin | Cabrio, Headline, Insignia Comet | Pristine (pyraloclostrobin + boscalid) |
| Bayer CropScience Trifloxystrobin | Compass, Flint, Gem, Twist | Stratego (Trifloxystrobin + propiconaz |
1 Excellent against Blast of rice
2 Recommended against Blast and Sheath blight of rice