Introduction

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To delay fungicide resistance/insensitivity:
• Where possible, rotate the use of a fungicide, (and others within the same Group) with different Groups that control
the same pathogens.
• Where possible, tank mix fungicides with a high risk of developing insensitivity with other fungicides from a different
Group.
• DO NOT apply more than the maximum number of applications listed on the label. Avoid consecutive sprays of a
fungicide, or other fungicides in the same Group, in a season.
• Fungicide use should be based on an integrated pest management (IPM) program that includes scouting and accurate
recording related to pesticide use and crop rotation. An IPM program also considers cultural, biological and other
chemical control practices.
• Monitor treated fungal populations for signs of fungicide insensitivity. If disease continues to progress after treatment
with a product, DO NOT increase the use rate. Discontinue use of the product and switch to another fungicide with a
different target site of action.
• Contact your local regional crops specialist or certified crop advisor for any additional pesticide management and/or
IPM recommendations for specific crops and disease problems in your area.
Fungicide Modes of Action
Why are fungicides needed?
• Control of disease during crop establishment.
• Increase productivity of crop (photosynthesis) and/or reduce blemishes.
º Maintain yield and/or market value.
• Improve storage life and quality of harvested plants / grain / produce.
º Prevent spoilage and/or production of mycotoxins.
How do fungicides work?
There are several ways to define ‘mode of action’:
• Timing:
º Preventative: fungicide must be present on plant surface before the pathogen and repeated applications are
required to protect new growth.
º Curative: pathogen may already be present (post-infection, pre-symptom kick-back activity).
º Eradicant: (post-symptomatic activity).
º Inhibitive: prevents spore germination or sporulation.
• Placement:
º Contact (AKA protectant): immobile – must come in direct contact with the pathogen.
º Systemic (AKA penetrant): mobile – can move within plant.
• Movement:
º Intra-plant Movement: within crop via vapour phase or redistribution by rain.
º Passive Absorption – by diffusion.
º Apoplastic Movement: xylem-mobile; move within free space and cell walls, upward through the transpiration
stream (with water).
º Symplastic Movement: phloem-mobile (common characteristic of herbicides and insecticides but very few
fungicides).
• Spectrum:
º General, Non-specific, or Broad Spectrum: fungicide affects pathogen in multiple ways.
º Specific or Narrow Spectrum: fungicide targets a specific metabolic site in pathogen or against critical enzyme or
protein. Genetic changes or naturally insensitive fungi have a greater chance to overcome the fungicidal effect
(resistance/insensitivity).
• Composition:
º Inorganic Fungicides: sulfur or metal ions such as copper.
º Organic Fungicides: contain carbon atoms.
º Biopesticides: suppressing pest populations using naturally occurring organisms or natural products derived from
plants.
Foliar Fungicides