key terms for fungicides - purdue university · inorganic fungicides sulfur (elemental) blocks...

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Foliar Fungicides for Control of Soybean Rust –How do they actually work?

Wayne PedersenPlant Pathologist

National Soybean Research LabUniversity of Illinois

Key Terms for Fungicides

Non-systemicLocally systemicSystemic

Proceedings of Indiana Crop Adviser Conference 2004

© Purdue University

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Key Terms for Fungicides

PreventativeCurativeEradicantAntisporant

(definitions from Jim Frank, Syngenta)

Preventative Fungicides

“Prevents the establishment of an infection on the host crop”



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Curative Fungicides

“ Interrupts the development of an established infection which is not showing visible disease symptoms on the plant”

Eradicant Fungicides

“Interrupts the development of an established infection which is showing visible disease symptoms on the plant”



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Antisporant Fungicides

“Prevents the fungus from producing spores or decreases spore production without stopping the vegetative growth of the pathogen”

1. Preventative Fungicides

Chemical barrierNot absorbed or translocatedPresent before infectionNo “kick-back” activityAffected by environmentCoverage is criticalInsurance



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Inorganic Fungicides

Sulfur (elemental)Blocks enzymes and stops respirationLimited spectrumMulti-site mode of action

Mercury CompoundsEnvironmental concernsVapor action-systemic (smuts)

Organic Fungicides

OrganometallicsDithiocarbamatesEBDCPhthalimidesSubstituted benzenesPhenylpyrroles



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Organometallics

Copper sulfateBordeau MixtureWide spectrumPrevents spore germinationMulti-site mode of action

DithiocarbamatesProtectantThiram (seed treatment)Multi-site mode of actionInterferes with oxygen uptakeInhibits sulfur-containing enzymesCauses allergic reactionLow risk of resistance



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EBDC’s

Maneb, mancozebCommon foliar fungicideParent product is not activeDegrades to cyanide (active)Low risk of resistance

Substituted Benzenes

PCNB (one ingredient in Rival)Broad spectrumLyses mitochondria membranesMay inhibit several enzymesLow risk of resistance



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PhthalimidesCaptanBroad spectrum Multi-site actionDegrades to thiophosgeneInhibits several enzymesLow risk of resistanceCaptan was RPAR’d in 1980

Phenylpyrroles

Maxim (fludioxonil)Broad spectrumAffects membrane transportLow risk of resistanceVery low use rates



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2. Curative Fungicides

Can “cure” an infectionSystemic ???Coverage is not as criticalHas ‘kick-back” activityWorks better with scoutingResistance management is important

Benzimidazoles

Benlate (benomil)Broad spectrumSystemicDoesn’t affect oomycetesInhibits beta-tubulinHigh risk of resistance



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Phenylamide

Apron XL (mefenoxam)Allegiance (metalaxyl)SystemicInhibits RNA synthesisControls oomycetesHigh risk of resistance

Sterol Inhibitors

TriazolesStrobulinsBenzathiadiazoles



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Triazoles

Tilt, Folicur, DividendBroad spectrumInhibits sterol biosynthesisSingle-site mode of actionHigher risk of resistance

Strobulin’s

Quadris, Headline, FlintSeveral new ones are comingDisrupts electron transport system (ETS)Systemic (xylem only)Higher risk of resistance??



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Benzathiadazoles

Actigard (SAR inducer)Spectrum unknown, but control many fungal pathogensStimulate natural resistance systems

Soybean Rust

Highly aggressive pathogenNo high level resistance in US germplasmMay require fungicides for control



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Labeled for soybean rust

Quadris (azostrobin)Bravo or Echo (preventative)

Section 18 Products…..propiconazole (Tilt)tetraconazole (Folicur)myclobutanil (Laredo)propiconazole+trifloxystrobin (Stratego)tetraconazole (Domark)pyraclostrobin (Headline)pyraclostrobin+boscalid (Pristine)



key terms for fungicides - purdue university · inorganic fungicides sulfur (elemental) blocks...

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