Fungicides and their MOAs

•Mode of Action (MOA)

–Refers to the specific biochemical or physiological process (or processes) that are affected by a compound.

•Target Site

–The actual biochemical that is affected in a given process or pathway

PROTECTANT

Fungicide does NOT enter the plant; coats outside of the leaf, stem, etc.

Must be applied BEFORE infection occurs!

•SYSTEMIC

–Fungicide is translocated in the plant and offers some (limited) curative activity.

Systemic (translocated) vs. “locally systemic

•Multi-site inhibitor

–A compound that affects more than one biochemical process or structural site

–Tend to be less prone to development of resistance

–Tend to be protectant-type compounds

•Single-site inhibitor

–Affects a specific process or pathway

–Very prone to development of resistance

–Tend to by systemic to some degree

What is Sulfur’s MOA? Target Site?

–Disrupts mitochondrial electron transport (Respiration pathway). It is a multisite that binds to H+ ions

Copper

non-specific denaturation of proteins and enzymes through sulfhdyryl (-SH) groups. It is a multisite that targets nucleus. (inorganic)

What are the two inorganic fungicides?

Copper and Sulfur

What is a common misnomer for single-site pesticides?

Single site pesticides are not cheaper than multicite necessarily.

What are the benefits and cons on single site over multicite?

Goods

Single sight is more selective

Typically safer due to only hitting one site

Lower doses required

Sometimes more effective

Bads

High chance of resistance

What are organic chemicals?

Synthetic fungicides that contain carbon in their chemical makeup (also hydrogen and oxygen commonly).

What are the 4 multisite Organic Inhibitors

•Dithiocarbamates, •Ethylene-bis-dithiocarbamates, •Chloronitriles, •Phthalimides

•Dithiocarbamates, •Ethylene-bis-dithiocarbamates, MOA. Target site?

MOA:–SH groups, disrupts production of amino acids, proteins, and enzymes (nucleus). They are multi-site so it is all SH groups/Nucleus

•Chloronitriles MOA. Target Site?

–Inactivate amino acids, proteins and enzymes by combining with amino and thiol groups. Multi-site but hits Nucleus. (organic)

•Pthalimides

MOA:–Interfere with mitochondrial respiration at multiple sites (organic)

•Phenylamides MOA and target site.

MOA: Disrupts fungal growth and germination.

•Target site is RNA polymerase I

Benzimidazoles

Thiophanates

MOA and Target site.

MOA:Prevents cell division by disrupting spindle development in Nucleus.

Target:•Inhibit β-tubulin synthesis in mitosis

•Anilinopyrimidines:–Cyprodinil (Vanguard®, Switch®)

–Pyrimethanil (Scala®)

–Melampyrin (Frupica®)

MOA and Target site.

MOA:AA disruptors and protein sythesis inhibitors.

Target site: cystathionine βbeta B-lyase (CBL) enzyme.

SDHI’s

MOA:cellular respiration disruptors

Target Site":succinate dehydrogenase of Complex II of mitochondria

•Strobilurin (Qol) MOA and Target Sites [includes other -strobins]

MOA:Targets cytochrome bc1 (ubiquinol oxidase) at the Qo (quinone outside) site in mitochondria (cellular respirartion)

Target Site:part of Complex III of mitochondrial respiration (Outside portion)

How was strobilurin (Qol) discovered

It was a naturally occurring mushroom defence chemical that was synthesized.

cyazofamid (QIL’s) []

MOA and Target Site

MOA:Targets cytochrome bc1 (ubiquinol oxidase)

at the Qi (quinone inside) site

Target Site:part of Complex III of mitochondrial respiration (inside portion)

What is bad about QIL’s

Only target oomycetes and plasmodiophora

•Triphenyl tins (organometallic compound)

MOA and Target Site

•Inhibit oxidative phosphorylation, ATP synthase.

•Quinolines and •Phenylpyrroles

MOA and Target Sites

Inhibiting early fungus-plant signaling events and interfering with

the fungus’ ability to make the morphological changes necessary

for infection

•Dicarboximides

MOA:Prevents cell membrane formation

Target site:–Targets NADH cytochrome c reductase in lipid peroxidation

•Aromatic hydrocarbons and heteroaromatics

MOA:Prevents lipids needed for membranes

target site:–Targets lipid peroxidation

What is the key component of cell walls that SBI’s inhibit?

•Ergosterol

•Sterol biosynthesis inhibitors (SBI’s)

MOA:Inhibit Ergosterol formation resulting in no membrane

Target Site:Prevents Lanosterol from converting to ergosterol via C14-demethylase

•Cinnamic acid derivatives

MOA:Inhibits spore germination and motility in water molds via cell wall disruption

Target site:Glucans that would make cell walls

•Isobenzofuranone

•Pyrroloquinolinone

•Triazolobenzothiazole

MOA:–all inhibit the production of melanin by

Target site:the enzyme reductase in melanin biosynthesis

Acibenzolar-s-methyl (Actigard)

Harpin (Messenger)

MOA:Cause host plant immune response

What are the two unknown chemical MOA’s?

•Cyanoacetamide oxime

•Phosphonates

How are strobilurin and cyazofamid different despite both attacking complex 3?

Strobilurin-outside

Cyazofamid-inside (only oomycetes and plasmodiphoria aswell)