Methods for Minimizing Fungicide Resistance in Plasticulture - - PowerPoint PPT Presentation

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Methods for Minimizing Fungicide Resistance in Plasticulture - - PowerPoint PPT Presentation

Nov 30, 2022 224 likes •604 views

Methods for Minimizing Fungicide Resistance in Plasticulture Strawberry Systems Phillip M. Brannen Systemic Fungicides Not as systemic as you may think. When fungicide is sprayed on one leaf, it is not readily moved to other unsprayed

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Methods for Minimizing Fungicide Resistance in Plasticulture Strawberry Systems

Phillip M. Brannen

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Systemic Fungicides

 Not as systemic as you may think.  When fungicide is sprayed on one leaf, it is

not readily moved to other unsprayed leaves. Coverage is still very important.

 Systemic fungicides can move within the

xylem (transpiration stream) in a leaf, resulting in more uniform distribution than that achieved by the initial deposit.

Principles of Disease Management; Fry (1982)

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Principles of Resistance Management

 Alternating sprays with fungicides from different

classes (different modes of action) is an important means of resistance management.

 Tank-mixing of different fungicides is also an

acceptable method of resistance management, and both methods are employed.

 Many fungicides are limited to a set number of

applications per year in order to improve their long-term survival. Follow the label recommendations.

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Tank Mixing Fungicides for Resistance Management

 Good resistance management tool.  Do not use half rates of a systemic and a contact,

since disease control would be poor and resistance management would be poor (unless known synergy

  • ccurs).

 Contact usually works very quickly, and systemic may

have moderately delayed action, so combination is sometimes good.

 Alternation is a good resistance management scheme,

and the cost issue is avoided.

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Resistance Management

 Use the fungicidal rate which results in complete

kill or deactivation of the fungus.

 Reducing rates is a dangerous game, since the

end result may be a “training” of resistant strains.

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www.frac.info

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R = resistant S = sensitive

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Evolution of fungicide resistance: quantitative resistance

Deising H et al. Brazilian Journal of Microbiology (2008) 39:286-295

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Evolution of fungicide resistance: qualitative resistance

Deising H et al. Brazilian Journal of Microbiology (2008) 39:286-295

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Acero et al. Int. J. Mol. Sci. (2011) 12:795-816

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  • 1. Use cultural practices to reduce carryover

inoculum.

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  • 1. Use cultural practices to reduce carryover

inoculum.

  • 2. Bring in clean, disease-free plants.
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Phytophthora crown and root rot

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Botrytis gray mold

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Powdery mildew

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  • 1. Use cultural practices to reduce carryover

inoculum.

  • 2. Bring in clean, disease-free plants.
  • 3. When possible, use fungicides which are not

prone to resistance development, such as Captan and Thiram.

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  • 1. Use cultural practices to reduce carryover

inoculum.

  • 2. Bring in clean, disease-free plants.
  • 3. When possible, use fungicides which are not

prone to resistance development, such as Captan and Thiram.

  • 4. Check the resistance status of your pathogens

(when possible).

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Collecting gray mold from fruit

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No Resistance

1 2 3 4 5 6

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1 2 3 4 5 6

High Resistance

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Summary

Monitoring results from 8 states, 2012

No resistance Moderate-high risk of resistance

20 40 60 80 100 T-methyl Pyraclostrobin Boscalid Cyprodinil Fenhexamid Iprodione Fludioxonil % Switch Switch (fludioxonil) Rovral Elevate Switch (cyprodinil) Pristine (boscalid) Pristine (pyraclostrobin) Topsin M

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  • 1. Use cultural practices to reduce carryover

inoculum.

  • 2. Bring in clean, disease-free plants.
  • 3. When possible, use fungicides which are not

prone to resistance development, such as Captan and Thiram.

  • 4. Check the resistance status of your pathogens

(when possible).

  • 5. Avoid fungicides which are exceptionally prone

to resistance development.

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Schnabel and Perez

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  • 1. Use cultural practices to reduce carryover

inoculum.

  • 2. Bring in clean, disease-free plants.
  • 3. When possible, use fungicides which are not

prone to resistance development, such as Captan and Thiram.

  • 4. Check the resistance status of your pathogens

(when possible).

  • 5. Avoid fungicides which are exceptionally prone to

resistance development.

  • 6. Spray as little as possible.
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www.smallfruits.com

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Path Forward

(1) Continue and expand monitoring for resistance. (2) Incorporate new fungicides with different modes of action, and determine efficacy of

  • ther fungicides and combinations.

(3) Incorporate novel approaches to management, such as timing sprays.