using fungicides more effectively
TRANSCRIPT
Using Fungicides More Effectively: Understanding Mode of Action and Other CharacteristicsDr. Frank WongDr. Frank Wong
University of California University of California RiversideRiversideDepartment of Plant Pathology Department of Plant Pathology & Microbiology & Microbiology Nursery/Floriculture Insect and Nursery/Floriculture Insect and Disease Management Disease Management SymposiumSymposiumWatsonville Elks Lodge Watsonville Elks Lodge October 28, 2010October 28, 2010
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Fungicide BasicsFungicides are pesticides that specifically kill fungi or inhibit fungal developmentAbout 40 different classes of fungicides used for plant protectionClasses are based on target site and biochemical mode of action
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Many work by breaking the molecular bonds that hold proteins togetherOthers smother or otherwise physically damage the fungus
Multi-site Inhibitors
SS
SH
SH
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EBDCsChlorothalanil
Copper++
Sulfur Multi-site Inhibitors
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Single-site InhibitorsAffect a specific metabolic processBind to proteins via “lock and key” process
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Single-site InhibitorsAmino Acid and Protein Synthesis
AnilinopyrimidinesSterol Biosynthesis
DMIsRespiration (MET complex III)
QoIsOsmoregulation (unknown)
Phenylpyrroles
Lipid BiosynthesisSub. Aromatic HydrocarbonsDicarboxymides
mRNA SynthesisPhenylamides
Nuclear DivisionBenzimidazoles
Respiration (MET complex II)
Carboxins
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Systemicity
Do not penetrate into plant Redistribute on plant surfacesMulti-site inhibitorsKills spores/inhibits germinationProtectant onlyBroad spectrum
Penetrate into plantRedistribute on & within plantsSingle-site inhibitorsInhibits spore germination and or mycelial growthProtectant and curativeSelective
Non-systemic Systemic
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Non-systemicsMimimal redistribution from the point of depositionWorks by contact with the fungusAdequate coverage is essentialOn the cuticleRedistributed washed off by water
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SystemicsLocal Systemic
Local redistribution from the point of depositionOn the cuticleThrough the leaf (translaminar)Extent is variable
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SystemicsLimited systemic (acropetal penetrant)
Good movement from the point of applicationThrough tissuesInside the vasculatureBulk movementDMIs, Phenylamides
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SystemicsTrue Systemics (Basipetal penetrant)
Only phosphonatesMoves through plantDown into rootsGood against soil-borne oomycetes
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Physical Mode of Action
© 1998 Novartis Crop Protection
© 1998 Novartis Crop Protection © 1998 Novartis Crop
Protection
© 1998 Novartis Crop Protection
germinationgermination sporulationsporulationcolonizationcolonizationinfectioninfection
protectantprotectant postpost--symptomsymptompostpost--infectioninfection
Fungicides tend to work best against spore germination and formation, and are less effective against mycelial growth
inside the plant
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Selection for Resistance
Initial Population Resistant Population
Survivor Population
Reproduction
The development of Practical Resistance is a step-wise process
Naturally occurring resistant individual
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Cross-ResistanceOnce resistance develops to a fungicide all fungicides with the same biochemical mode of action are affected“Cross-resistance class” is defined as a class of fungicides that share the same biochemical mode of action and mechanism of resistanceExample: all DMI fungicides
all affect sterol biosynthesisa change in the fungal enzyme affects all DMIs
Fungicide Group M Multi-site fungicides“Old but reliable workhorses”
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Group MAll “contact” fungicides with a non-specific mode of action are represented in this classCoppersMancozebChlorothalonilBicarbonatesOilsSulfur
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Group MPros
InexpensiveModerate range of activity depending on AINo resistance risk
ConsFoliar diseases only Short application intervals
Group 1 Fungicides Methyl Benzimidazole Carbamates“Broad spectrum vs Ascomycetes and Basdiomycetes but beware of resistance”
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Group 1: Benzimidazole FungicidesInhibit nuclear division during cell replication by binding to beta-tubulin
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Group 1: MBC (Benzimidazole) FungicidesBroad spectrum of activity
Ascomycetes (Botrytis, Powdery Mildew, Leaf Spots)Basidiomycetes (Rhizoctonia, Rusts)
Systemic, acropetal penetrant fungicidesCurative abilitiesThiophanate-methyl – Clearys 3336
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Group 1: MBC (Benzimidazole) FungicidesPros
Broad spectrum of activity vs ascomycetes and basidiomycetesSystemic acropetal penetrant activity Lasting residual activity & long application intervals
ConsNot effective vs. OomycetesDevelopment of resistance for some diseases
Group 2 Fungicides Dicarboximides“Proven chemistry for Botrytis and Rhizoctonia”
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Group 2: DicarboximidesFunction by inhibiting osmotic regulation pathways in fungi (os-2)Local penetrant fungicidesIprodione – Chipco 26019
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Group 2: Dicarboximides
Treated Untreated
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Group 2: DicarboximidesPros
Strong vs Botrytis & RhizoctoniasControl of leaf spotsGood vs Fusarium but not 100% effective
ConsLocal penetrant activity only No powdery mildew activtyNo Oomycete activitySome tolerance present in Botrytis
Group 3 Fungicides Sterol Demethylation Inhibitors
“Good enough for my feet and many Ascomycete and Basidiomycete diseases”
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Group 3: DMI FungicidesInhibit demethylation of ergosterol used in cell membranesCalled SBI, SI or DMI fungicides Widely used for plants, animals and medical purposes Systemic, acropetal penetrant fungicides
Fenarimol - RubiganMyclobutanil - HoistPropiconazole - Banner MAXXTriadimefon – StrikeTriflumazole - Terragaurd
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Untreated
Treated
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Group 3: DMI FungicidesPros
Strong vs powdery mildew, Rhizoctonia, rust and some leaf spots Good curative activity & lasting effects
ConsSome plant growth regulator effects at high rates or high temperaturesLimited activity vs Botrytis No activity vs Oomycetes
Group 4: Phenylamides
“Your Oomycete specialist”
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Group 4 : PhenylamidesThese are Ooymcete- specific fungicidesMefenoxam - Subdue MAXX
Inhibits RNA polymerase and protein synthesis
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Group 4 : PhenylamidesPros
Very effective vs Pythium, Phytophthora, and Downy MildewsStrong protectant and curative activity
ConsDoes not work against Ascomycetes & BasidiomycetesResistance likely if over used
Group 7 Fungicides Succinate Dehydrogenase Inhibitors“A growing class of fungicides with a diverse spectrum of activity”
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Group 7: SDHI FungicidesAffect mitochondrial respiration by binding to succinate dehydrogenase in complex IIDifferent fungicides in this group that share the same mode of action but have very different ranges of activity Flutolanil - RhizoctoniaBoscalid - Botrytis & powdery mildew
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Group 7: SDHI FungicidesUse in nursery/floriculture is “limited” at this timeBoscalid + pyraclostrobin is the ‘Pageant’ combinationExpect more SDHIs to be coming in the market
Group 11 Fungicides Qo-Inhibitors“Broad-spectrum strobies + narrow range non-strobies in the same class”
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Group 11: Qo-InhibitorsTwo distinct groups of chemicals that target mitochondrial respirationStrobilurins
Azoxystrobin (Heritage)Kresoxim-methyl (Cygnus)Pyraclostrobin (Insignia)Trifloxystrobin (Compass)
Non-strobilurinsFenamidone (Fenstop)
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QoI Class of Chemistry
OO
ON
ON
FF
F
CN
O O
N N
OO
O
O
OON
O
OO
O
O
N
NN
ClS
NN
ON
H
StrobilurinsBroad-spectrum
Non-strobilurinsNarrow-spectrum
Fenamidone
Kresoxim-methyl
Pyraclostrobin
Trifloxystrobin
Azoxystrobin
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Group 11: Qo-InhibitorsQoIs shut down respiration in mitochondiraStrongest vs. spore germinationSome have stronger curative or systemic properties than others
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Group 11: QoIsPros
Broad spectrum vs all fungal classes for some strobiesSystemic, local to acropetal penetrant activity Lasting residual activity & long application intervals
ConsFenamidone only good vs. OomycetesLess systemic fungicides not very good for root infecting and soil fungi High risk resistance for some diseases
Group 12 Fungicides Phenylpyrroles“Nature’s gift vs. Botrytis, Fusarium & Rhizoctonia”
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Group 12: PhenylpyrrolesFunction by inhibiting osmotic regulation pathways in fungi (os-1)Derived from a natural product derived from a soil Pseudomonad Local penetrant fungicide Good soil stability Fludioxonil (Medallion)
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Treated Untreated
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Group 12: PhenylpyrrolesPros
Strong vs Botrytis, Fusarium & RhizoctoniasGood soil stability
ConsLocal penetrant activity only, strongest as a preventive applicationNo activity vs. Oomycetes, powdery mildew or rusts
Group 14 Fungicides Aromatic Hydrocarbons
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Group 14: Aromatic HydrocarbonsChemically similar but different range of activity
PCNB: Rhizoctonia & Sclerotinia, some Botrytis activity for stored bulbsEtridiazole (Terrazole): Pythium and Phytophthora only
Affects lipid (membrane) synthesisNon-systemic
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Group 14: Aromatic HydrocarbonsPros
Good control of soil borne diseases Cons
Possible long term restriction on PCNB use due to contaminant toxicity issues Limited activity of etridiazoleContact only, best as a preventive application
Group 17 Hydroxyanalides“Your neighborhood Botrytis specialist”
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Group 17: HydroxyanalidesA sterol-biosynthesis inhibitor with a different site of action than the DMIsFexhexamid (Decree)Systemic and curative propertiesWorks great vs. Botrytis, but almost nothing else other than Botrytis Some activity vs. powdery mildew but not a selling point
Group 19 Fungicides Polyoxins“Smells like Ramen – works great vs Rhizoctonia, and has Botrytis and mildew activity”
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Group 19: PolyoxinsFunction by inhibiting cell wall (chitin) synthesisDeveloped originally as a Rhizoctonia fungicide from natural products derived from Streptomyces soil microbesLocal penetrant fungicide Polyoxin-D (Veranda O)
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Group 19: PolyoxinsPros
Strong vs RhizoctoniasGood activity vs Botrytis & some powdery and downy mildews
ConsLocal penetrant activity only Does not control Pythium, Phytophthora, rusts and certain mildews
Group 21 Qi-Inhibitors“The inside pocket Oomycete fungicide”
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Group 21: Qi-InhibitorsAffects mitochondrial respiration; same enzyme as the QoIs, but on the “inside” binding site Systemic and curative propertiesCyazofamid (Segway)Only affects Oomycetes
Group 33 Fungicides Phosphonates
“Oomycete fungicides that can go up & down inside the plant”
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Group 33: PhosphonatesUnknown mode of action Unique that they can move upwards and downwardsActive vs. Pythium, Phytophthora & downy mildewsFosetyl-Al (Aliette, Signature)Phosphite salts (Alude)
Group 40 Carboxylic Acid Amine (CAA) Fungicides
“The downy mildew & Phytophthora specialist”
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Group 40: CAA FungicidesInhibit cell wall formation Systemic and curative propertiesHighly effective vs. downy mildews and Phytophthora – no Pythium activity Dimethomorph (Stature)
Combination Fungicides“Multi-purpose in a jar”
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Combination FungicidesMixtures combine the effectiveness of different fungicides for broad-spectrum activity Useful and avoids having to tank-mixKnow the properties of the tank mix partnersAnti-resistance strategy?Sort of – still have to worry about overuse of single-site partners
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Combination FungicidesMixtures combine the effectiveness of different fungicides for broad-spectrum activity Useful and avoids having to tank-mixKnow the properties of the tank mix partnersAnti-resistance strategy?Sort of – still have to worry about overuse of single-site partners
Group 44 Microbials“Bacteria with their own fungicide factories”
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Group 44: MicrobialsBacillus subtilis bacteria formulated as pesticide (Serenade, Companion, etc.)These produce lipopeptides that disrupt fungal cell membranesEffective vs Botrytis, Fusarium, powdery mildew, rust, downy mildewsBest as a preventive foliar material May require short application intervals May break under heavy disease pressure
Trichodermas“It’s a fungus eat fungus world out there”
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TrichodermasThere are at least 2 species used as pesticidesDirectly attack other fungi
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TrichodermasEffective vs Botrytis, Rhizoctonia, Pythium and some PhytophthorasMay require short application intervalsMay be affected by fungicide applications May break under heavy disease pressure
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Questions???Questions???