Disease – Manage Resistance Now

DISEASES

DISEASES

Fungicide resistance has the potential to affect all crops grown in Canada, and is already an issue in several crops including pulses, potatoes and fruit. Effectively managing fungicide resistance requires multiple strategies to ensure plants are healthy and to promote the longevity of fungicides. Ultimately, this will help maintain yield and quality and manage fungicide resistance.

WEEDS

INSECTS

FUNGICIDE RESISTANCE BEST MANAGEMENT PRACTICES

Resistance best management practices (BMPs) include a combination of physical, cultural, biological and chemical control measures. Start today to manage fungicide resistance on your farm.

USE AGRONOMIC PRACTICES THAT PROMOTE HEALTHY PLANTS

Use multiple strategies to optimize healthy plants:

Use resistant varieties or cultivars for problematic diseases in your area. For example, if you know that net blotch is an issue on barley in neighbouring fields, plant a variety that is resistant or moderately resistant to this disease.
Know what environmental conditions contribute to disease development and be aware of disease issues in previous years. Monitor and manage high-risk areas separately.
Rotate field crops to reduce pathogen populations. Diseases can persist on stubble, in some weed populations, in soil between seasons and over the winter. Rotating crops helps break the cycle.
Reduce crop stress by: optimizing planting date, planting at the proper seed depth, using high-quality seed, controlling other pests, and minimizing herbicide injury.
Use quality seed treatments when possible. For some crops, soil- and seed-borne pathogens can be a source of disease.

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Test Your Knowledge about Agronomic Practices that Promote Healthy Plants

1. Optimizing healthy plants includes strategies such as:
(select all that apply)

A. Using resistant varieties
B. Planting susceptible crops to increase disease tolerance
C. Rotating crops
D. Reducing crop stress
SHOW ANSWER Answer: A, C and D — Be aware of disease issues in previous years and avoid planting susceptible crops in high risk areas.

2. Sources of disease include:
(select all that apply)

A. Stressed crops
B. Crop stubble
C. Soil
D. Weeds
SHOW ANSWER Answer: B, C and D — Disease pathogens can persist in crop stubble, in certain weeds, and in soil. Stressed crops are more susceptible to disease but are not in themselves a source of disease.

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EVALUATE THE NEED FOR DISEASE CONTROL

Assess your level of disease risk in your crop for that year based on agronomic factors (for example crop type and stage), disease issues in previous years, and environmental conditions in the current year. For some pathogens, such as late blight, Sclerotinia, Fusarium Head Blight and apple scab, preventative fungicide applications can be beneficial.
Scout fields to identify problems and assess early and often. Correctly determine the level of disease risk before deciding whether fungicides are needed.
If you have a high disease risk based on agronomic and environmental factors, very early fungicide applications can be beneficial to prevent populations from getting out of control. For example, forage crops should be scouted for leaf spots prior to head emergence (grasses) or the vegetative to early bloom stages (legumes).
Be aware that different diseases have different levels of risk to resistance.
Minimize the number of treatments applied per season, and apply only when necessary. Follow the product label and do not exceed the number of applications permitted per year.
Review cultural practices and environmental conditions and apply fungicide if risk to yield or quality is greater than cost of application.
Scout after application and use unsprayed check strips to evaluate the application’s effectiveness.
Keep and regularly review records to make good crop management decisions from year to year.
Consult with a crop advisor to help troubleshoot strategies as required.

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Test Your Knowledge about Evaluating the Need for Disease Control

Before deciding whether a fungicide is needed it is important to:
(select all that apply)

A. Scout fields
B. Correctly identify the disease to understand how prevalent it is
C. Leave unsprayed check strips
D. Consult with a crop advisor
SHOW ANSWER Answer: A, B and D — All of the above except “C” are steps to take before deciding whether to spray. Unsprayed check strips are a good way to evaluate fungicide effectiveness by comparing with sprayed areas.

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SELECT FUNGICIDES STRATEGICALLY

Use fungicides that are labelled for the diseases that pose a threat to your crop yield.
Some pathogens are more likely to develop resistance and some fungicides are easier for diseases to develop resistance to. Know the risk level in your crop/disease combination to help you choose effective cultural practices and products.
Fungicide groups have been classified according to their level of risk. The Fungicide Resistance Action Committee (FRAC) groups codes are used to distinguish the different fungicide groups based on their mode of action (MoA) and their resistance risk. Click here for a list of fungicides and their resistance risk level.
Rotate fungicide groups both during a growing season and between growing seasons, either through tank mixes or alternating sprays with fungicides that have different modes of action but work on the same target disease.
Mix fungicides. Combinations of two or more fungicides with different modes of action against the targeted pathogen, applied as a mixture at the recommended rates according to label directions, can delay the onset of resistance. For a mixture to be truly multi-mode of action, both modes of action need to be effective on the same disease species.
Avoid using at-risk fungicides when possible.

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Test Your Knowledge about Selecting Fungicides Strategically

1. Group codes are on all fungicide labels. Which of the below are true about fungicides with the same group code?
(select all that apply)

A. They have the same mode of action
B. Diseases resistant to a fungicide will generally be more or completely resistant to other fungicides in the group
C. They have a similar resistance risk level
SHOW ANSWER Answer: All of the above are true

2. To maximize resistance management properties of a fungicide mixture you must consider:
(select all that apply)

A. If the fungicides have different modes of action (group codes)
B. Wind conditions on the date of spray
C. Whether the different modes of action are effective against the same disease
D. Individual resistance risk levels of the fungicides
SHOW ANSWER Answers A, C and D — should be considered when using fungicide mixtures.

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MAXIMIZE FUNGICIDE EFFICACY

Use in-crop scouting and/or verified predictive models to determine the need and optimal timing of spray application. Consult the product label for the most effective time to spray.
Be mindful of proper spray techniques and adequate water volumes when applying fungicides, whether the disease is foliar, seed, or tuber. When there is more foliage, spraying will require a greater water load to ensure adequate coverage and control disease.

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Test Your Knowledge about Maximizing Fungicide Efficacy

Checking the product label and scouting are both important when determining the most effective time to spray.

True
False Answer: True — The product label indicates the most effective time to spray, while crop scouting will help determine the level of disease and need for fungicides

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