Fungicide Table
The fungicides listed in Table 1 have been divided into groupings based upon their general mode of action and specific disease control requirements. The key to effectiveness ranges from excellent, good, fair or poor to no labeled activity, and is based upon results of other researchers or our own results in trials conducted at Freeville, NY. Fungicide groups are arranged according to the classification used by the Fungicide Resistance Action Committee (FRAC). The protectant or contact fungicides with multi-site activity (groups M1, M3, M5 and Group 30) are listed first, and consist of fixed coppers (not all available coppers are listed), the EBDCs (ethylene bisdithiocarbamates), the chloronitriles (chlorothalonil), and the tin fungicides. Copper fungicides do not perform as well as the standard protectants, and are included for use by organic operations. The remaining protectant fungicides form the backbone of most spray programs since when used preventatively, they are effective against early and late blight. They may be combined with other fungicides in tank mixtures or used in alternate spray weeks to allow for the rotating of fungicide chemistries. EBDC usage has increased as formulations have improved and they are less expensive than the chlorothalonil-based products.

            If late blight is found on your farm, then fungicides listed in the second half of the table should be consider, especially the “Late Blight Plus” grouping. These include the currently NYS-registered products Curzate, Gavel, and Previcur Flex. Curzate and Previcur Flex need to be tanked with one of the protectant fungicides listed in the first part of the table. Note that some of these products are systemic, in that they move in the xylem to provide coverage to the leaf tips (acropetal movement), and also provide tuber blight protection. Currently the only strobilurin fungicides labeled in the state are Quadris or Amistar or the product Quadris Opti (a premix of azoxystrobin and chlorothalonil). These are all group 11 fungicides and need to be rotated with other fungicides from a different grouping (mode of action) to prevent resistance concerns. The strobilurins are very effective against early blight, but need to be used at the highest labeled rate for late blight control.

Fungicide Resistance
Fungicide resistance is not as big an issue in New York mainly because we have been conservative in the use of fungicides that, because of their single mode of action, are prone to developing resistance. This is the case for the strobilurin fungicides (like Quadris, Headline and Gem) which were used extensively in the mid-west and far-west potato production areas, and now have reduced sensitivity to the early blight fungus. Adherence to the labeled use of strobilurins (a strict one to one rotation with products with a different mode of action, and limiting the number of applications per season to 1/3 of the total applications) will preserve this valuable class of fungicides here in New York. Resistance of mefenoxam (one ingredient in Ridomil Gold Bravo and Flouronil) to the oomycete organisms responsible for Pink rot and Pythium leak has been reported in other states, but has not been verified in New York. Insensitivity of mefenoxam to the new genotypes of late blight remains an issue for the most common US 8 isolate. The other fungicide for which resistance is an issue is Mertect (thiabendazole) and its use as a post harvest treatment. In New York, at least half of the Fusarium population is resistant to this product.

Fungicide Usage and Weather Conditions
The cool and wet conditions that we currently are encountering are especially conducive for Late Blight. High disease severity values and the common occurrence of potato volunteers only heighten the concern. Spray programs should follow a preventive schedule when plants reach the 4-6 inch stage, and need to be followed weekly while we remain under these highly favorable conditions. Consideration should also be given to fields later in the season where standing water has been an issue. These conditions are very conducive for the occurrence of Leak and Pink rot.

            If more summer-like conditions occur, then grower concerns will shift to the occurrence of Early Blight and Black Dot. A good selection of fungicides are available for early blight control, but the key for adequate disease control is to apply fungicides before this disease gets the upper hand. Early blight is more aggressive when plants are weakened by a loss of nitrogen due to early season leaching. This is likely to be a factor this season. High temperatures above 88 F during late July and continuing into August is sure to stress plants, and will allow black dot to become an issue. Research in our plots has shown that in stressful years (between 10 and 20 days above 88 F), that the use of two or three strobilurin sprays (Quadris, Amistar or Quadris Opti) can reduce the occurrence of black dot on stems and tubers, and generally increase specific gravity by 2 or more points.

Table 1. Foliar Potato Fungicides (Registered, Not Registered in NYS; Days To Harvest; Effectiveness where E = Excellent; G = Good; F = Fair; P = Poor or no activity) (June 2004)

Fungicide Groups and Trade Names

Common Name

Manufacturers/ Distributor

Registration,DTH

Early Blight

Late Blight (Foliage)

Late Blight (Tubers)

Black Dot

Rhizoctonia

White Mold

Pink Rot

Pythium Leak

Comments and Resistance Management

Protectants Multi-site activity

Coppers (Group M1)

• Basicop

basic copper sulfate

Dupont

R, O

F

F

P/?

P

P

P

P

P

Contact only

• Cuprofix Disperss

basic copper sulfate

Cerexagri

R, O

F

F

P/?

P

P

P

P

P

Contact only

• Champ, • Champion

copper hydroxide

Nufarm

R,O

F

F

P/?

P

P

P

P

P

Contact only

• Kocide

copper hydroxide

Dupont

R,O

F

F

P/?

P

P

P

P

P

Contact only

EBDC (Group M3)

• Dithane

mancozeb

Dow

R, 3

G

G

F/?

F

P

P

P

P

Contact only; mixing partner or alternating product

• Manzate

mancozeb

Dupont

R, 3

G

G

F/?

F

P

P

P

P

Same

• Penncozeb

mancozeb

Cerexagri

R, 3

G

G

F/?

F

P

P

P

P

Same

• Maneb

maneb

Cerexagri

R, 3

G

G

F/?

F

P

P

P

P

Same

• Manex

maneb

Dupont

R, 3

G

G

F/?

F

P

P

P

P

Same

• Clean Crop Polyram

metiram

UAP

R, 14

G

G

F/?

F

P

P

P

P

Same

• Polyram

metiram

BASF

R, 14

G

G

F/?

F

P

P

P

P

Same

Fungicide Groups and Trade Names

Common Name

Manufacturers/ Distributor

Registration,DTH

Early Blight

Late Blight (Foliage)

Late Blight (Tubers)

Black Dot

Rhizoctonia

White Mold

Pink Rot

Pythium Leak

Comments and Resistance Management

Chloronitrile (Group M5)

• Bravo • Echo

chlorothalonil

Syngenta Sipcam

R, 7

E

E

F/?

G

P

P

P

P

Contact only; mixing partner or alternating product

Tins (Group 30)

• Agri Tin† • Super Tin†

triphenyltin hydroxide

Nufarm Dupont

R, 7

G

G

F/?

P

P

P

P

P

Contact only; mixing partner or alternating product

Strobilurins (Group 11)

• Quadris, Amistar

azoxystrobin

Syngenta

R, 14

E

G

F/?

E

G

P

P

P

Alternate with non-strobilurins

• Headline

pyraclostrobin

BASF

NR

E

G

F/?

E

P

P

P

P

Same

• Gem

trifloxystrobin

Bayer

NR

E

G

F/?

G

P

P

P

P

Same

• Tanos (Group 11 + Group 27)

famoxadone + cymoxanil (tank mix with M3)

Dupont

NR

E

E

F/?

G/?

P

P

P

P

Treat as contact; alternate with M3 and M5

• Quadris Opti

azoxystrobin + chlorothalonil

Syngenta

R, 14

E

G

F/?

E

G

P

P

P

Alternate with non-strobilurins

Fungicide Groups and Trade Names

Common Name

Manufacturers/ Distributor

Registration,DTH

Early Blight

Late Blight (Foliage)

Late Blight (Tubers)

Black Dot

Rhizoctonia

White Mold

Pink Rot

Pythium Leak

Comments and Resistance Management

Late Blight plus

• Acrobat MZ (Group 15)

dimethomorph + mancozeb

BASF

NR

G

E

G

P

P

P

P

P

Systemic (acropetal); tuber blight activity

• Curzate (Group 27)

cymoxanil (tank mix with M3)

Dupont

R, 14

G

G

F/?

P

P

P

P

P

Systemic (acropetal); tank mix

• Gavel (Group 22)

zoxamide + mancozeb

Dow

R, 3

G

E

G

P

P

P

P

P

Treat as protectant; tuber blight activity

• Omega (Group 29)

fluazinam

Syngenta

NR

P

G

G

P

P

E

P

P

Contact activity only; tuber blight activity

• Previcur Flex (Group 28)

propamocarb (tank mix with M3 or M5)

Bayer

R, 14

G

E

G

P

P

P

P

P

Systemic activity; tuber blight activity

Dicarboximide

• Rovral (Gp 2)

iprodione

Bayer

R, 14

G

P

P

P

P

G

P

P

Contact activity

Benzimidazole carbamate

• Topsin M (Group 1)

thiophanate-methyl

Cerexagri

R, 21

P

P

P

P

P

G

P

P

Can be tank mixed with other fungicides

Comments and Resistance Management

Common Name

Manufacturers/ Distributor

Registration,DTH

Early Blight

Late Blight (Foliage)

Late Blight (Tubers)

Black Dot

Rhizoctonia

White Mold

Pink Rot

Pythium Leak

Comments and Resistance Management

Others

• Endura (Group 7)

boscalid

BASF

NR

E

P

P

P

P

G

P

P

Systemic (acropetal) and translaminar

• Phostrol • ProPhyt (Group 33)

phosphorous acid

Nufarm Helena

R,O

P

F

P/?

P

P

P

F

F

Control limited to oomycetes tank mix with M3 to improve and expand diseases controlled (3DTH for most)

• Ridomil Gold Bravo • Flouronil (Group 4 + Group M5)

mefenoxam + chlorothalonil

Syngenta Nufarm

R, 14

F

P

P/?

P

P

P

G

G

Control limited to oomycetes and depends upon absence of fungicide resistance

† Restricted use pesticide. Mention of a product or manufacturer/distributor does not constitute an endorsement, and a guarantee is not made to the accuracy or completeness of the information contained here. Not all copper fungicides available have been mentioned, and not all fungicide formulations have been given.

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