Most common turfgrass diseases are caused by fungi. Fungicides kill or inhibit the growth of fungi.
There are two general categories of fungicides:
- contact/protectant
- penetrant
Contact/protectant fungicides remain on the outside of the plant and protect the plant from new infection. They must be applied at comparatively short intervals that can range from 5 to 14 days, because the fungicides are degraded by ultraviolet light, washed from the leaf surface by irrigation or rain, or mowed away. These fungicides do not have curative activity and new growth is not protected. Thorough coverage of plant tissue is critical to successful protection. Examples of contact/protectant fungicides commonly used in turf include captan, chlorothalonil, chloroneb, etridiazole, fluazinam, fludioxonil, mancozeb, maneb, PCNB, and thiram.
Penetrant fungicides are absorbed into plant tissue and may provide some curative action. The duration of control afforded by penetrant fungicides is often much longer than that offered by contact fungicides, and some redistribution into new tissue may occur as the plant grows. Application intervals vary, but often range from 14 to 21 days and longer. According to specific topical modes of action, penetrant/systemic fungicides can be further divided into three sub-categories:
- Localized penetrants form a protective barrier on the plant surface and permeate into the leaf in the area where deposition occurred. These fungicides have some curative activity, but do not move upward or downward inside the plant. Examples include iprodione, polyoxin D zinc, trifloxystrobin, and vinclozolin.
- Acropetal penetrants form a protective barrier on the plant, permeate into the plant, and move upward in the plant’s xylem. These fungicides have protective activity including new growth, and have good curative activity. Examples include azoxystrobin, fenarimol, mefenoxam, and triadimefon.
- Systemic penetrants form a protective barrier on the plant, permeate into the plant, move upward in the plant’s xylem, and move downward in the plant’s phloem. These fungicides have protective activity including new growth, and have good curative activity. Of the currently available penetrant/systemic fungicides, only fosetyl-Al (Aliette Signature) is truly systemic and moves both upward and downward in the plant.
Refer to Table 20 for a list of available fungicide materials and their respective topical modes of action.
Fungicide resistance
Some fungicides are site specific in their mode-of-action. This means that it takes very little genetic change on the part of a fungus for resistance to occur. Resistance may result in poor disease control, meaning that higher application rates or shorter intervals are needed to maintain healthy turf, or complete control failure. Resistance may develop suddenly or gradually depending on the fungicide involved. Once resistance has developed in a fungal population, it may last for a long time or gradually disappear if the fungicide is no longer used, depending on the fungicide and site-specific factors. Resistance is common for some diseases, but not observed for others. Fungicide resistance has been documented for anthracnose, dollar spot, Microdochium patch, gray leaf spot, and Pythium blight.
The best strategy is to try to prevent, or at least delay, resistance. All penetrant fungicides are at risk for resistance development due to their “single-site” mode-of-action. Contact/protectant fungicides are unlikely to result in resistance because most of them have “multi-site” modes-of-action with the exception of fludioxonil (Medallion) and a few others which have a “single-site” mode-of-action. There are multiple chemical groups with different biochemical modes-of-action for broad-spectrum disease control in turfgrass that are at risk for resistance. Fungicide resistance has already been reported in five of these groups (Benzimidazole, Dicarboximide, Demethylation Inhibitor (DMI), Strobilurin (QoI) and Phenylamide).
Table 19. Turfgrass pathogens and chemical classes with documented fungicide resistance.
Turfgrass Disease (causal agent) | Resistance to chemical classes (see Table 20) | ||||
---|---|---|---|---|---|
Benzimidazole | Dicarboximide | DMI | QoI | Phenylamide | |
Anthracnose (Colletotrichum cereale) | X | X | X | ||
Dollar spot (Sclerotinia homoeocarpa) | X | X | X | ||
Gray leaf spot (Pyricularia grisea) | X | ||||
Microdochium patch/pink snow mold (Microdochium nivale) | X | ||||
Pythium blight (Pythium aphanidermatum) | X |
Mix or alternate between different site-specific chemical groups or with multi-site contact/protectant fungicides, indicated by different FRAC (Fungicide Resistance Action Committee) code numbers, to prevent or delay the development of resistance. Changing fungicides by brand or trade name will not prevent resistance if the active ingredient or chemical group is the same. Fungicide labels list the active ingredient(s) in smaller letters below the brand name. Be especially careful when using combination (pre-mixed) products, which may include fungicides subject to resistance prevention strategies. Tables 20-22 list fungicide materials along with their corresponding FRAC codes for ease of reference.
Guidelines to prevent or delay resistance to turf fungicidesMinimize disease conditions
Make proper fungicide choices
Know the material
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Table 20. Chemical classes, trade names and topical modes of action of fungicides registered for use on turf.
Common Name | FRAC 1 | Group Name | Trade Name(s) | Topical mode of action 2 |
---|---|---|---|---|
azoxystrobin |
11 |
Strobilurin (QoI) |
Heritage (50WG, TL, G) |
Acropetal Penetrant |
boscalid |
7 |
Succinate Dehydrogenase Inhibitor |
Emerald 70EG |
Acropetal Penetrant |
captan |
M4 |
Phthamlimides |
Captan (50W, 50WP, 4L), Captec 4L |
Contact |
chloroneb |
14 |
Aromatic Hydrocarbon |
Terraneb SP, Teremec SP, Andersons Fungicide V, Proturf Fungicide V |
Contact |
chlorothalonil 3 |
M5 |
Chloronitrile |
Andersons 5% Daconil 5G, ArmorTech (825 DF, CLT 720), Concorde SST 6F, Daconil (5G, 2787, Zn, Ultrex, WeatherStik), Echo 720F, Ensign 720, Equus 500ZN, Manicure (6FL, Ultra), Lebanon Daconil 5G, Legend, Pegasus (6L, DFX, HPX) |
Contact |
cyazofamid |
21 |
Quinone inside Inhibitors (QiI) |
Segway |
Localized Penetrant |
etridiazol (ethazole) |
14 |
Aromatic Hydrocarbon |
Koban, Terrazole 35WP, Truban |
Contact |
fluazinam |
29 |
Uncoupler of oxidative phosphorylation |
Secure |
Contact |
fludioxonil |
12 |
Phenylpyrrole |
Medallion (WDG, WP) |
Contact |
fluoxastrobin |
11 |
Strobilurin (QoI) |
Fame 480SC |
Acropetal Penetrant |
flutolanil |
7 |
Succinate Dehydrogenase Inhibitor |
ProStar 70WP, Moncut 70-DF |
Acropetal Penetrant |
fluxapyroxad |
7 |
Succinate Dehydrogenase Inhibitor |
Xzemplar |
Acropetal Penetrant |
fosetyl-Al (Aluminum tris) |
33 |
Phosphonate |
Autograph, Chipco Aliette, Chipco Signature, Chipco Signature Xtra, Lesco Prodigy Signature, Viceroy 70DF |
Systemic Penetrant |
iprodione |
2 |
Dicarboximide |
Andersons Fungicide X, ArmorTech IP 233, Chipco 26 GT, Chipco 26019, Iprodione Pro, Lesco 18 Plus, Proturf Fungicide X, Raven |
Localized Penetrant |
isofetamid |
7 |
Succinate Dehydrogenase Inhibitor |
Kabuto |
Acropetal Penetrant |
mancozeb |
M3 |
Dithiocarbamate |
Dithane 75DF, Fore Rainshield 80WP, Junction, Lesco Mancozeb DG, Lesco 4 Flowable Mancozeb, Manzate Pro-Stick 200, Protect DF, WingMan (4L, DF) |
Contact |
mandestrobin |
11 |
Strobilurin (QoI) |
Pinpoint |
Acropetal Penetrant |
maneb |
M3 |
Dithiocarbamate |
Maneb 80WP, Maneb 75DF, Pentathalon (LF, DF) |
Contact |
mefenoxam |
4 |
Phenylamide |
Andersons Pythium Control, Mefanoxam, Subdue MAXX |
Acropetal Penetrant |
metalaxyl |
4 |
Phenylamide |
Subdue 2E, Subdue GR, Subdue WSP, Apron (seed treatment), Vireo MEC |
Acropetal Penetrant |
metconazole |
3 |
Demethylation Inhibitor |
Tourney |
Acropetal Penetrant |
myclobutanil |
3 |
Demethylation Inhibitor |
Andersons Golden Eagle, Eagle 20EW, Siskin |
Acropetal Penetrant |
PCNB (pentachloronitrobenzene or quintozene) |
14 |
Aromatic Hydrocarbon |
Andersons FFII 15.4G, Defend 4F, Engage 75W, Fluid Fungicide II, Lesco Revere 4000 4F (10G), Parflo 4F, PCNB 12.5G, Penstar 75WP, Terraclor 400F (75WP), Turfcide 400F (10G) |
Contact |
penthiopyrad |
7 |
Succinate Dehydrogenase Inhibitor |
Velista |
Acropetal Penetrant |
phosphite (salts) |
33 |
Phosphonate |
Appear, Alude 5.2F, Biophos, Fiata Stessguard, Fosphite, Jetphiter, Magellan, Phostrol, Reliant, ReSyst 5F, Vital 4L |
Systemic Penetrant |
polyoxin D zinc salt |
19 |
Polyoxin |
Endorse 2.5WP, Affirm 11.3WDG |
Localized Penetrant |
propamocarb |
28 |
Carbamate |
Banol 6S |
Localized Penetrant |
propiconazole |
3 |
Demethylation Inhibitor |
ArmorTech PPZ 143, Banner GL, Banner MAXX II, Kestrel, Lesco Spectator, Procon-Z, ProPensity, Propiconazole Pro 1.3MEC, PropiMax, Strider |
Acropetal Penetrant |
pyraclostrobin |
11 |
Strobilurin (QoI) |
Insignia Intrinsic SC, Insignia |
Localized Penetrant |
tebuconazole |
3 |
Demethylation Inhibitor |
Clearscape, Mirage Stressguard, Tebuconazole 3.6F, Torque, Skylark, |
Acropetal Penetrant |
thiophanate-methyl |
1 |
Benzimidazole |
Allban, Andersons Systemic Fungicide 2.3G, ArmorTech TM 462, Cleary's 3336 (F, WP, DG lite, G, GC, Pro-Pak, Plus), Fungo (Flo, 50WSB), Lesco T-Storm 2G, Systec, T-Bird (4.5L, WDG), Tee-Off 4.5F, T-Methyl SPC 50 WSB, TM (4, SF, 85WDG) |
Acropetal Penetrant |
thiram |
M3 |
Dithiocarbamate |
Defiant 75WDG, Thiram, Spotrete F |
Contact |
triadimefon |
3 |
Demethylation Inhibitor |
Accost 1G, Bayleton (50WSP, Flo), Andersons Fungicide VII 0.59G, Andersons 1% Bayleton 1G, Lebanon Bayleton 1G |
Acropetal Penetrant |
trifloxystrobin |
11 |
Strobilurin (QoI) |
Compass 50WDG |
Localized Penetrant |
triticonazole 5 |
3 |
Demethylation Inhibitor |
Trinity, Chipco Triton (70WDG, Flo) |
Acropetal Penetrant |
vinclozolin |
2 |
Dicarboximide |
Curalan 4F, Touché EG |
Localized Penetrant |
1 Fungicide Resistance Action Committee (FRAC) Code: fungicides with the same FRAC code have the same mode of action. M-codes indicate multi-site chemicals with low risk of resistance development. It is recommended to rotate applications by FRAC code and not to make sequential applications of fungicides with the same FRAC code.
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Updated October 2017 |
Table 21. Pre-mixed fungicide products registered for use on turf.
Pre-mixed Products (Common Name) | FRAC 1 | Trade Name(s) |
---|---|---|
azoxystrobin + chlorothalonil 2 |
11 + M5 |
Renown |
azoxystrobin + difenconazole |
11 + 3 |
Briskway |
azoxystrobin + propiconazole |
11 + 3 |
Headway, Headway G, Contend B |
Benzovindulflupyr + difenconazole |
3 + 7 |
Contend A |
chlorothalonil 2 + acibenzolar-S-methyl |
M5 + P1 |
Daconil Action |
chlorothalonil 2 + propiconazole |
M5 + 3 |
Concert II, Echo Propiconazole Turf Fungicide |
chlorothalonil 2 + tebuconazole |
M5 + 3 |
E-Scape ETQ |
chlorothalonil 2+ thiophanate-methyl |
M5 + 1 |
Broadside, ConSyst, Peregrine, TM/C WDG, Spectro |
chlorothalonil 2 + fludioxonil + propiconazole |
M5 + 12 + 3 |
Instrata |
chlorothalonil 2 + iprodione + tebuconazole + thiophanate-methyl |
M5 + 3 + 3 + 1 |
Enclave |
fluoxastrobin + chlorothalonil 2 |
11 + M5 |
Fame C |
fluoxastrobin + tebuconazole |
11 + 3 |
Fame T |
fluopyram + trifloxystrobin |
7 +11 |
Exteris |
iprodione + trifloxystrobin |
2 + 11 |
Interface Stressguard |
mancozeb + copper hydroxide |
M3 + M1 |
Junction |
mancozeb + myclobutanil |
M3 + 3 |
MANhandle |
propamocarb + fluopicolide |
28 + 43 |
Stellar |
pyraclostrobin + boscalid |
11 + 7 |
Honor |
pyraclostrobin + fluxapyroxad |
11 + 7 |
Lexicon |
pyraclostrobin + triticonazole 3 |
11 + 3 |
Pillar G Intrinsic |
thiophanate-methyl + chloroneb |
1 + 14 |
Proturf Fungicide IX |
thiophanate-methyl + flutolanil |
1 + 7 |
SysStar |
thiophanate-methyl + iprodione |
1 + 2 |
ArmorTech TMI 20/20, 26/36 Fungicide, Dovetail, Lesco Twosome, Proturf Fluid Fungicide |
thiophanate-methyl + mancozeb |
1 + M3 |
Duosan (WP, WSB) |
triadimefon + flutolanil |
3 + 7 |
Prostar Plus |
triadimefon + trifloxystrobin |
3 + 11 |
Armada |
triadimefon + trifloxystrobin + stress guard |
3 + 11 |
Tartan Stressguard |
1 Fungicide Resistance Action Committee (FRAC) Code: fungicides with the same FRAC code have the same mode of action. M-codes indicate multi-site chemicals with low risk of resistance development. It is recommended to rotate applications by FRAC code and not to make sequential applications of fungicides with the same FRAC code. 2 Use of chlorothalonil is regulated in Massachusetts under the Public Drinking Water Supply protection regulation, see the Pesticide Regulations section of this guide for details. 3 Use of triticonazole is regulated in Massachusetts under the Public Drinking Water Supply protection regulations, see the Pesticide Regulations section of this guide for details. |
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Updated October 2017 |