Fungicide Resistance

A fungicide disrupts either energy producing reactions or a chemical building (synthesis) reaction within the target fungus.
Fungicide Resistance - Articles
Fungicide Resistance

Phytotoxicity caused by multiple applications of chlorothalonil fungicide.

The way it kills the fungus is termed the fungicide's 'mode of action.' Certain fungicides, usually systemics, have very specific modes of action and are said to be 'at risk' to the development of resistance. An 'at risk' fungicide may bind to a very specific chemical within the fungus or disrupt one specific step required for the reaction. If the fungus has an alternate pathway to complete the reaction, can break down the fungicide or prevents the chemical from acting in the fungus, then the fungus is resistant to that fungicide. It is generally accepted that there is a great deal of variation within populations of fungi and a few individuals in the population naturally are resistant to certain types of chemicals. When the chemical is used, it kills almost all of the sensitive individuals in the population but the survivors are those few individuals resistant to the action of the chemical. The survivors give rise to the next generation and most of that generation is resistant to the chemical.

It is recommended that high risk (1 = low risk; 3 = high risk) chemicals be used sparingly, used in rotation with, or mixed with chemicals with different modes of actions. Fungicide Resistance Action Committees (FRAC) developed a numbering system in which chemicals that have the same mode of action have the same FRAC group number. When selecting chemicals for rotation or mixing, select ones with different FRAC Group numbers (see below) because then you are using ones with different modes of action.

Listed below are some of the commonly used fungicides. Not all fungicides are listed. Chemical, trade names, and availability change frequently. This is not a complete list. It may not be up to date because items change daily.

FRAC GroupClassActive ingredientREI Restricted Entry IntervalTrade names (EPA reg. no.)
1Benzimidazolethiophanate methyl123336 (1001-69)
OHP 6672 (51036-329-59807)
Fungo Flo (51036-329-59807)
Systec 1998 (48234-12)
debacarbFungisol (7946-14)
2Dicarboximideiprodione12Chipco 26GT (100-1138)
Chipco 26019 (264-481)
Iprodione (51036-361)
OHP 26 (432-888-59807)
Sextant (51036-361-59807)
vinclozolin12Curalan (7969-62-58185)
3Imidazoletriflumizole
imazalil
12
24
Terraguard (400-433)
Fungaflor (499-508)
PyrimidinefenarimolRubigan (62719-134)
Piperazinetriforine12Triforine (241-355)fenamidone
fenamidone12FenStop (432-1389-59807)
Triazolepropicoonazole24Banner MAXX (100-741)
Propiconazole (51036-403)
Spectator (62719-346-10404)
Kestrel (66222-41-81943)
triadimefon12Strike (3125-436)
Bayleton (432-1360)
tebuconazoleTeuject (7946-24)
myclobutanil24Systhane (707-253)
Rally (62719-410)
4Acylaninemefenoxam0Subdue MAXX (100-796)
Fenox (70252-11-48234)
5Piperidinepeperalin24Pipron (67690-1)
7Anilide (carboxamide)flutolanil12Contrast (45639-208-58185)
ProStar (432-1477)
11Strobilurinazoxystrobin4Heritage (10182-408)
kresoxim-methyl12Cygnus (7969-124)
pyraclostrobin12Insignia (7969-184)
trifloxystrobin12Compass (432-1371)
12Phenylpyrolfludioxonil12Medallion (100-769)
14Aromatic hydrocarbonPCNB12Revere (400-407-10404)
Blocker (5481-211)
Terraclor (400-399)
Defend (5481-444-1001)
Thiadiazoleetridiazole12Truban (58185-7)
Terrazole (400-416)
Banrot (58185-10)
17Hydroxyanilidefenhexamid4Decree (66330-35-67690)
19Polyoxinpolyoxin4Veranda (66330-56-459807)
Endorse (66330-41-1001)
21QilcyazofamidSegway (71512-13-279)
25Glucopyranosyl antibioticstreptomycinStreptomycin (66222-121)
28Carbamatepropamocarb12Banol (432-942)
Previcur Flex
40Cinnamic acid derivativedimethomorph12Stature (241-419-67690)
41Tetracycline antibioticoxytetracyclineBacastat (74779-2)
Mycoject (7946-18)
MPhthalimidecaptan96Captan (66330-29)
Chloronitrilechlorothalonil48
12
12
48
12
12
Daconil (50534-9)
Echo (60063-7)
PathGuard (60063-7-499)
Exotherm Termil (70-223)
Concorde (72167-24-1812)
Pegasus (72167-24-1812)
Copper, complexcopper sulfate12
24
Camelot (1812-381)
Phyton 27 (49538-3)
Copper, fixedcopper hydroxide48Kocide (352-656)
cupric hydroxide48Champion (55146-1)
Dithiocarbamatemancozeb24Dithane (707-180)
FORE (707-87)
Junction (1812-360)
Pentathlon (1818-251)
manganese + zinc24Protect T/O (1001-65)
ferbam24Ferbam (45728-7)
ziram48Ziram (4581-140)
UPhosphonatefosetyl-Al12Aliette (432-890)
Phosphitephosphorus acid salts4Alude (71962-1-1001)
ArborFos (7946-26)
potassium phosphite4Vital (42519-24)
NCpotassium bicarbonate4Armicarb (5905-541-AA)
Milstop (70870-1-68539)
Kaligreen (70231-1)
Remedy (62719-70)
Agricure (70870-1-1001)
sodium hypochloriteClorox (5813-55)
hydrogen dioxideZeroTol (70299-1)
TerraClean (70299-5)
neem oil4Trilogy (70051-2)
Triact (70051-2-59807)
paraffinic oil4JMS Stylet Oil 65564-1)
Ultra-Fine Oil (862-23-499)
petroleum oilPureSpray (69526-9)
potassium salts of fatty acids12M-Pede (62719-515)
sulfur24Kumulus (51036-352)
Combined products
4 + 12mefenoxam + fludioxonil48Hurricane (100-951)
11 + 7pyraclostrobin + boscalidPageant (7969-251)
M + Mmancozeb + copperJunction Fungicide (1812-360)
1 + Mthiophanate methyl + chlorothalonilSpectro 90(1001-72)
ConSyst (48234-7)
1 + Mthiophanate methyl + etridiazoleBanrot (58185-10)
Zyban (58185-31

Group Mode of action

  1. Inhibits tubulin formation
  2. Inhibits RNA or DNA synthesis
  3. DMI (demethylation inhibitor), inhibits sterol synthesis
  4. Inhibits RNA synthesis
  5. Inhibits isomease in sterol synthesis
  6. Disrupts electron transport in mitochondria
  7. Disrupts beta-tubulin assembly
  8. Quinone outside inhibitors (QOI)
  9. Disrupts osmotic signal transduction
  10. Disrupts lipid peroxidation
  11. Disrupts cell wall synthesis
  12. Disrupts C4 demethylation in sterol biosynthesis
  13. Disrupts protein synthesis
  14. Affects membrane permeability
  15. Uncouples oxidative phosphorylation
  16. Disrupts phospholipids and cell wall deposition
  17. Protein synthesis attachment of tRNA to ribosomal receptor
  18. Disrupts proteins involved in stabilizing cell membranes during growth

M Multi-site activity

P Host plant defense induction

U Unknown mode of action

NC Not classified

Authors

Gary W. Moorman, Ph.D.