QoI working group of NAFRAC

The NAQoI working group of the North American Fungicide Resistance Action Committee (NA-FRAC) was first established in 1999 with the goal to achieve harmonization of resistance management guidelines to QoI fungicides, after it was recognized that this group of fungicides carries a high risk for resistance development. The QoI's (Quinone Outside Inhibitors) which include azoxystrobin, dimoxystrobin, enestroburin, famoxadone, fenamidone, fluoxastrobin, kresoxim-methyl, metominostrobin, orysastrobin, picoxystrobin, pyraclostrobin, pyribencarb, trifloxystrobin are assigned to FRAC Group 11.

The NAQoI members Bayer Crop Science, BASF, DuPont, Arysta and Syngenta have been working in collaboration with the international QoI working group toward the harmonization of labels in both North America and Europe and have achieved significant harmonization of resistance management guidelines both on the labels for QoI fungicides and in the application of QoI’s in agriculture and specialty crops.

Resistance management with the QoI's presents many thorny problems because this class has a high risk for resistance development. Although resistance has been reported on many crops and diseases in many different countries around the world, the products remain valuable tools for disease control. Resistance management begins with good agricultural practice, resistant varieties, sanitation, healthy seed, and disease forecasting. The language added to the label is the last line of defence against resistance development. The label will typically require minimum effective rates and will require a combination of mixing chemicals or alternation of chemicals that have different modes of action, and/or restricting the number of applications used during a season. Representatives from the companies attending the NAQoI-meetings were able to agree on the basic strategy for resistance management in North America. NAQoI places emphasis on formulating guidelines that are sufficiently straightforward for the end-user to follow in his plant disease management program.

Contact People

Name Company Email Address
Gilberto Olaya Syngenta gilberto.olaya@syngenta.com
Allison Tally Syngenta Allison.tally@syngenta.com
Bond McInnes DuPont bond.mcinnes@usa.dupont.com
George Musson Bayer Crop Science george.musson@bayer.com
Scott Walker BASF scott.l.walker@basf.com

Guidelines for use of QoI-containing fungicides in North America

The following general guidelines for QoI fungicide use in North America were discussed with the international FRAC-QoI working group and agreed upon on January 14, 2003, and subsequently efforts will now be made by the NAQoI-group to simultaneously incorporate these guidelines into the North American QoI fungicide labels. This process will take both time and coordination between the manufacturers and the regulatory agencies. Therefore, not all labels currently in circulation will immediately reflect the guidelines presented below. The NAQoI guidelines are in general accordance with those of the international Qo Inhibitor working group, but specific for use in North America and are based on the following guidelines:


The general and crop-specific guidelines focus on the number of foliar applications of QoI-fungicides. Due to the generally very limited uptake of the currently marketed QoI’s at registered dose rates from the seed or plant root to the upper parts of the plant, and consequently minimal effects on foliar pathogens, seed treatment or in-furrow applications utilizing QoI fungicides are not counted as foliar applications to determine the maximum number of sequential sprays or the total number of sprays per season.

  1. Total number of applications per season: Limit the number of QoI applications per season or per crop where necessary (see below).

  2. Sequential number of applications: Limit the number of sequential QoI applications and apply QoI’s in alternation with labeled fungicides with a different mode of action at effective dose rates.

  3. Application timing with respect to disease development: Apply QoI’s preventatively.

  4. Use of tank mixtures: Use tank mixtures with fungicides from different target site of action Groups that are registered/permitted for the same use and that are effective against the pathogens of concern. The NAQoI-group recommends using at least the minimum labeled rates of each fungicide in the tank mix.

  5. IPM: Applications of fungicides, including those containing QoI’s, should be integrated into an overall disease and pest management program. Cultural practices known to reduce disease development should be followed. Consult your local extension specialist, certified crop advisor and/or manufacturer representative for additional IPM strategies established for your area. QoI-fungicides may be used in Agricultural Extension advisory (disease forecasting or risk assessment) programs, which recommend application timing based on environmental factors favorable for disease development.

  6. Product performance: Monitor efficacy of all fungicides used in the disease management program against the targeted pathogen and record other factors that may influence fungicide performance and/or disease development. If a Group 11 target site fungicide appears to be less effective against a pathogen that it previously controlled or suppressed, contact a manufacturer representative, local extension specialist, or certified crop advisor for further investigation.

Total number of applications of QoI-containing products per season – General

NAQoI has established the following general guidelines for the maximum number of applications of a QoI containing fungicide. In addition to that, the maximum number of applications may be restricted to a specific limit on a particular crop (see crop-specific recommendations):

Follow the specific crop recommendations that limit the total number of sprays on a crop and the required alternations with fungicides from other resistance management groups. In situations requiring multiple fungicide sprays, develop season long spray programs for Group 11 fungicides.

Use of Solo QoI products: When using a Group 11 fungicide as a solo product, the number of applications should be no more than 1/3 of the total number of fungicide applications per season. Use of QoI mixes: In programs in which tank mixes or pre-mixes of a Group 11 fungicide with a fungicide of another Group are utilized, the number of Group 11 fungicide (QoI)-containing applications should be no more than 1/2 of the total number of fungicide applications per season.

Use in programs in which both solo QoI’s and mixes are used: In programs in which applications of group 11 fungicides are made with both solo products and mixtures, the number of Group 11 fungicide (QoI)-containing applications should be no more than 1/2 of the total number of fungicide applications per season.

Guidelines on sequential number of applications of QoI-containing fungicides

Depending on the crop and resistance risk identified for the target diseases, NAQoI either recommends scenarios utilizing a maximum of one application of a QoI-containing fungicide alternated with at least one application of a fungicide of a different mode of action (1:≥1), or a maximum of two sequential applications of a QoI-containing fungicide alternated with at least two applications of one or more fungicides of a different mode of action (2:≥2).

Crops for which a 2: ≥2 rotation of QoI’s is the guideline are:

  • Cereals
  • Corn (field corn and field corn for seed)
  • Rice
  • Grasses grown for seed
  • Tropical Fruit
  • Turf (to control diseases other than Pythium, Gray Leaf Spot, Anthracnose)
  • Tree Nuts
  • Stone Fruits
  • Pome Fruit
  • Vine Crops
  • Citrus
  • Peanuts (in areas with typically a total 5 or more fungicide sprays per year)
  • Cane Berries
Crops for which a 1: ≥1 rotation of QoI’s is the guideline are:

  • Fruiting Vegetables
  • Root
  • Tuber and Corm Vegetables (including Potato)
  • Cucurbit Vegetables
  • Bulb Vegetables
  • Leafy Vegetables
  • Sweet Corn
  • Legumes
  • Strawberries
  • Peanuts (In areas with typically a total of 1-4 fungicide sprays per year)
  • Sugar beet – One application of a QoI-based fungicide application may be made up to the 4 leaf stage of plant growth. QoI applications made after the 4th leaf stage are alternated with labeled fungicides of other modes of action on a 1: ≥1 basis, independent of the single QoI application permitted prior to the fourth leaf stage.
  • Turf (for control of Pythium, Gray Leaf Spot, or Anthracnose)
  • All other Crops not Specifically Mentioned

Total number of applications of QoI containing products per season – Crop specific

NAQoI has established specific limits on the maximum number of applications of a QoI containing fungicide on the crops listed below. The maximum number of QoI fungicide applications will be limited by either the generally recommended proportion of QoI containing fungicides above or the specific maximum, whichever is less.

Crop Maximum number of QoI containing fungicide applications
Cereals and rice 2 per season
Corn (field corn and field corn for seed) 2 per season
Pome Fruits (all diseases) 4 per season
Citrus (all diseases) 4 per year
Cucurbits (all diseases) 4 per year

Other guidelines

Use of QoI-containing fungicides is not allowed in transplant production in greenhouses.
Use of QoI-containing fungicides is not allowed in citrus and strawberry nurseries



Dr. Gilberto Olaya

Syngenta Crop Protection
7145 58th Avenue
Vero Beach, FL 32967

Phone: 772-794-7149 

Email: gilberto.olaya@syngenta.com