1. Pesticide Management Fungicide Benefits & Challenges:
BSPM 451
H. F. Schwartz
Pesticide Management
Fungicide Benefits & Challenges:
Contribute to food safety by controlling many of the fungi that
produce mycotoxins.
Meet increasing demand for more food and higher quality food.
There are more than 125 active ingredients registered as fungicides worldwide.
Growing demand by the public for crop protection agents with:
low use rates, a benign environmental profile, and
low toxicity to humans and wildlife.

2. Fungicide Classification
Mobility in the plant
Role in protection of the plant
Breadth of metabolic activity
Mode of Action
Chemical group or class
FRAC code
Mueller et al. – Fungicides for Field Crops, 2013

3. Fungicide Classification
Mobility in the plant
Contact Fungicide
Remains on the plant where it is applied,
but is not absorbed into plant tissue; has no
postinfection activity; repeated apps may be needed
Systemic Fungicide
Moves into plant tissue, may have postinfection
activity; some move up plant in xylem tissue, some
are locally systemic within treated portion of plant
Mueller et al. – Fungicides for Field Crops, 2013

4. Fungicide Classification
2. Role in protection of the plant
Preventive (Protective) Activity
Occurs when fungicide present on plant as a
protective barrier before pathogen arrives or grows
Early Infection (Curative) Activity
Occurs when fungicide is absorbed by the plant and
stops the pathogen in early development (24-72 hrs)
Antisporulant Activity
Occurs when fungicide prevents spores from being
produced; lesions may develop but less inoculum
Mueller et al. – Fungicides for Field Crops, 2013

5. Fungicide Classification
3. Breadth of metabolic activity
Single-site Fungicide
A fungicide that is active against only one point of
function in one of the metabolic pathways of a fungus
or against a single critical enzyme or protein needed
by the fungus; may have systemic properties
Multi-site Fungicide
A fungicide that affects a number of different
metabolic sites within the fungus
Mueller et al. – Fungicides for Field Crops, 2013

6. Fungicide Classification
4. Mode of action
Is the means by which the fungicide kills or
suppresses a target fungus or affects specific
biochemical processes of the target fungus
Examples
Damaging cell membranes
Inactivating critical enzymes or proteins
Interfering with key processes (respiration, energy production)
Mueller et al. – Fungicides for Field Crops, 2013

7. Pesticide Management Mode of Action:
Fumigative - acts as vapor rather than a solid or liquid
Protectant - protective barrier between plant & agent
Systemic - taken up & distributed in the plant system
Acropetal = upward movement
Basipetal = downward movement
Symplastic = movement in phloem tissue
Ambimobile = movement in phloem & xylem

8. Fungicide Classification
5. Chemical group or class
Is a set of chemicals that have a common
biochemical mode of action; may or may not
have a similar chemical structure
6. FRAC Code
Fungicide Resistance Action Committee (FRAC)
developed a code of numbers and letters that are
used to distinguish fungicide groups based on their
modes of action
Mueller et al. – Fungicides for Field Crops, 2013

9. Fungicide Classification
Chemical Classes (Frac Code No.)
1 – Benzimidazole Carbamate
inhibit tubulin biosynthesis – mitosis in fungi
2 – Dicarboximide
interfere with osmotic signal – germination, mycelium
3 – Demethylation Inhibitor (DMI)
inhibit enzyme in sterol production – membrane & function
4 – Phenylamide
inhibit RNA synthesis – mycelial growth, spore formation
7 – Succinate Dehydrogenase Inhibitor (SDHI)
inhibit fungal respiration
Mueller et al. – Fungicides for Field Crops, 2013

10. Fungicide Classification
Chemical Classes (Frac Code No.)
9 – Anilino-Pyrimidine (AP)
inhibit synthesis of amino acids – fungal penetration & growth
11 – Quinone Outside Inhibitor (Qol)
inhibit respiration in mitochondria – spore germination & growth
12 – Phenylpyrrole (PP)
interfere with osmotic signal – spore germination & growth
14 – Aromatic Hydrocarbon (AH)
may interfere with lipid & membrane synthesis – mycelial growth
21 – Quinone Inside Inhibitor (Qil)
inhibit fungal respiration & energy production
Mueller et al. – Fungicides for Field Crops, 2013

11. Fungicide Classification
Chemical Classes (Frac Code No.)
22 – Benzamide
destroys microtubule assembly – fungal mitosis & cell division
27 – Cyanoacetamide-Oxime
activity is unknown – is a preventive during early infection
28 – Carbamate
interferes with synthesis of phospholipids and fatty acids
29 – Oxidative Phosphorylation Uncoupler
inhibit energy production – germination & infection structures
30 – Organo Tin Compound
inhibit fungal respiration
Mueller et al. – Fungicides for Field Crops, 2013

12. Fungicide Classification
Chemical Classes (Frac Code No.)
32 – Heteroaromatic
inhibit nucleic acid synthesis
33 – Phosphonate
inhibit spore germination & mycelial development, SAR
40 – Carboxylic Acid Amide (CAA)
affects formation of cell walls
M – Multisite Activity
are considered protectant or preventive fungicides; attack
multiple biochemical sites within the pathogen
Mueller et al. – Fungicides for Field Crops, 2013

13. Pesticide Management Fungicide Requirements:
1. Low lethal dosage to targeted organism
2. Noninjurious to the host
3. Nontoxic to man and animals
4. Imparts no undesirable flavor, odor, toxic properties
5. Compatible with other chemicals
6. Tenacious adherence to plant surface, resists weathering
7. Ease of preparation and application
8. Noncorrosive to containers, machinery, other objects
9. Low cost
Maloy - Plant Disease Control, 1993

14. Pesticide Management Toxicity:
Dose is expressed as the lethal dose required to kill a
certain percentage of a test population (e.g., 50 %)
[ LD50 of 30 means that 30 mg of chemical per kg body weight per
test animal is lethal to 50 % of the animals ]
Toxicity Groups:
High LD50 of < 50
Medium LD50 of
Low LD50 of > 500 (most fungicides)
[ e.g., thiram = 800, iprodione = 2000, captan = 9000 ]
Maloy - Plant Disease Control, 1993

15. Pesticide Management Fungicide Formulations: Wettable Powder (WP)
Dry Flowable (DF)
Dust (D)
Flowable (F)
Emulsifiable Concentrate (EC)
Liquid Concentrate (L, LC)
Granule (G)
Maloy - Plant Disease Control, 1993

16. Pesticide Management Fungicide Names:
Chemical Name (active ingredient):
methyl (E)-2-{2-[6-(2-cyanophenoxy)
pyrimidin-4-yloxy]phenyl}-3-methoxyacrylate
Class = Quinone inhibitor (Group 11)
Common Name:
Azoxystrobin
Trade Name:
Quadris

17. Pesticide Management Additional Information on Label:
Restricted Entry Interval (REI):
Minimum time between application of a pesticide to a field
and when it is safe to reenter that field;
usually hours for fungicides
Pre-harvest Interval (PHI):
Minimum amount of time that must pass between the last
pesticide application and harvesting of the crop or grazing;
usually 7-30 days for fungicides
Mueller et al. – Fungicides for Field Crops, 2013

18. Pesticide Management Fungicide Application:
Determined by:
- application equipment available
- formulation
- kind of crop
Methods:
Ground Duster
Vaporizer
Airplane
Chemigation Unit
Sprayer
High Volume (HV) at g/A
Medium Volume (MV) at g/A
Low Volume (LV) at g/A
Ultra-low Volume (ULV) at < 0.5 g/A

19. Pesticide Management Advantages of Seed Treatment:
1. Easily applied when properly done
2. Inexpensive compared to foliar sprays, soil drenches
3. Effective since every plant (seed) is protected
4. Supplement other control measures
Most seed-treatment fungicides kill or inhibit pathogens
on seed surfaces, but few kill pathogens embedded in the
seed coat. Fewer fungicides eradicate pathogens beneath
the seed coat. More recently developed materials are
low in phytotoxicity, narrow in range of activity, and
specific in mode of action.
Maloy - Plant Disease Control, 1993

20. Pesticide Management Eradicants other than Seed Treatment:
Dipping of transplants or seedlings
Fumigation - methyl bromide
Postharvest Disinfectants
sulfur dioxide, nitrogen trichloride, formaldehyde,
phenolic compounds, carbon dioxide, ozone
Maloy - Plant Disease Control, 1993

21. Pesticide Management Factors Affecting Soil Fumigation: Soil Texture
- range from sands ( > 85 % sand) to clays ( > 40 % clay)
- coarse textured soils are generally easier to fumigate
- the clay fraction absorbs large amounts of fumigant
Soil Structure (Porosity)
Soil Moisture
Soil Temperature
Organic Matter
Plant Residues
Maloy - Plant Disease Control, 1993

22. Pesticide Management Factors Affecting Soil Fumigation: Soil Texture
Soil Structure (Porosity)
- fumigants move through air passages and dissolve in
the water film
- too many or too large air channels allow fumigants to
diffuse too rapidly to be effective
Soil Moisture
Soil Temperature
Organic Matter
Plant Residues
Maloy - Plant Disease Control, 1993

23. Pesticide Management Factors Affecting Soil Fumigation: Soil Texture
Soil Structure (Porosity)
Soil Moisture
- thickness of water film is important for retaining gas in
soil since gas in soil air is in equilibrium with gas in the
soil water; optimal amount of soil moisture ( % of
field capacity) provides both an adequate water film and
large air passages
Soil Temperature
Organic Matter
Plant Residues
Maloy - Plant Disease Control, 1993

24. Pesticide Management Factors Affecting Soil Fumigation: Soil Texture
Soil Structure (Porosity)
Soil Moisture
Soil Temperature
- effectiveness increases with increasing temperatures,
affects fumigant volatility, movement through soil, and
postfumigant period before planting to reduce phytotoxicity
- best results are obtained at C
Organic Matter
Plant Residues
Maloy - Plant Disease Control, 1993

25. Pesticide Management Effective Disease Control: Proper Timing
Efficacy of the Fungicide
Good Coverage (placement, exposure)
Particle Size
Adhesion
Maloy - Plant Disease Control, 1993

26. ONION BACTERIAL DISEASES Disease Management
Colorado State University, 1998/99
Kocide 2000
+ Manex/Maneb:
10 x - Pre
6 - 9 x - Post
% Disease Reduction -----
% Increase
[ Untreated check: disease intensity = ratings during August to September, yield estimate
taken mid September; Xanthomonas Leaf Blight + Pantoea Blight ]

27. Buffered Oil & Organosilicate
ONION BACTERIAL DISEASES Disease Management
Water Control + Dye
48 %
Bond
46 %
Sun-It II
57 %
Sticker
Methylated Seed Oil
Kinetic
86 %
X - 77
Aero Dyne-Amic
81 %
78 %
Nonionic Surfactant
Nonionic Surfactant
Buffered Oil & Organosilicate
Notes:
1. max labeled rate of adjuvant in 18 gpa; 2. 1 g uv blue dye / 100 ml water; 3. % coverage = ave of 4 runs, 5 reps; 4. D. Gent & H. Schwartz, C S U

28. Pesticide Management Registration of Fungicides:
FIFRA = Federal Insecticide, Fungicide and Rodenticide
Act passed in 1947 for pesticide regulation
FDA = Food and Drug Administration in 1954 established
tolerances for food safety with the Miller Amendment
EPA = Environmental Protection Agency was created in
1970 for registration, testing, tolerances for federal label
Section 24c = special local need (SLN)
Section 18 = emergency crisis need
Maloy - Plant Disease Control, 1993

29. Management Options - Fungicides
Section 18 – Soybean Labels for Soybean Rust
Quilt (axozystrobin + propiconazole)
Laredo (myclobutanil)
Tilt, Propimax, Bumper (propiconazole)
Stratego (propiconazole + trifloxystrobin)
Folicur, Orius (tebuconazole)
Headline SBR (tebuconazole + pyraclostrobin)

30. Management Options: IR-4
Since 1963, the IR-4 Project has been the major resource for supplying pest management tools for specialty crop growers by developing research data to support new EPA tolerances and labeled product uses.
Major funding for IR-4 is provided from Special Research Grants from: * USDA-NIFA * USDA-ARS * USDA-FAS and * USDA-APHIS and is provided in cooperation with the State Agricultural Experiment Stations. These stations provide in-kind support valued at over $18 million annually.

31. Manage for Fungicide Resistance:
Use disease predictive models to effectively time fungicide applications
Scout fields frequently to monitor for early disease when conditions are conducive
Follow label recommendations – rate, interval, coverage, rotate fungicide groups
Integrated Pest Management Strategies

32. Pesticide Management Fungicidal Resistance:
Not a concern with older fungicides that are broad
spectrum and non-site-specific
Resistance is defined as a stable, inheritable adjustment
by a fungus to a fungicide, resulting in less than normal
sensitivity to that fungicide; is permanent
Tolerance is acquired or adaptive resistance, which is not
genetically transferable, and develops from exposure to
increasing concentrations of a fungicide; is reversible
Maloy - Plant Disease Control, 1993

33. Pesticide Management Fungicidal Resistance Mechanisms:
Reduced Permeability or Exclusion of Toxicants from Cells
Detoxification by Chemical Breakdown or Binding to
Nontarget Sites
Decreased Conversion into Toxicant
Modification of Sensitive Sites
[ some controlled by single genes, others by multiple alleles]
Maloy - Plant Disease Control, 1993

34. Pesticide Management Fungicidal Resistance Development Affected by:
Rate of Pathogen Sporulation and Dispersal
Ability of Resistant Strains to Compete (Fitness)
Threshold of Infection for Disease Development
Nuclear Condition (haploidy, diploidy, polyploidy) and
Nuclear Status (mono-, di-, or heterokaryosis)
Maloy - Plant Disease Control, 1993

35. Pesticide Management Fungicidal Resistance Management:
Integrate with nonchemical disease control measures
Apply only when needed and at recommended dosages
Select least specific fungicide that is available & effective
Use mixtures of specific and broad-spectrum fungicides
Mix application schedules (alternate fungicides)
Maloy - Plant Disease Control, 1993

36. Pesticide Management Integration with Other Technologies:
Implementation of IPM Systems
Enhanced Diagnostic Techniques -
precision agriculture + targeted fungicide applications,
diagnostic methods, forecasting models, remote sensing
Use of Natural Fungal Antagonists (Biological Control)
Crop Biotechnology - Enhancement of plant defenses by
transgenic crop modification & other techniques
Knight et al. - Ann. Rev. of Phytopath, 1997

37. Questions ?