Potato XXII – 12

Potato Foliar Fungicides

Gary D. Franc

Properly timed and properly applied foliar fungicides delay the onset of disease and will also slow the rate at which foliar disease develops.  Foliar fungicides are an important component of an integrated disease management program.  Thorough coverage, the proper rate and correct timing are necessary for successful disease management.

Late Blight

The causal organism, Phytophthora infestans, overwinters in infected potato tubers. The main source for initial inoculum is infected seed potatoes and infected potatoes discarded in cull piles. Fungicides are an important component of a comprehensive late blight management program. An application schedule based on environmental parameters (accumulated severity values) can effectively be used to time foliar fungicide applications.  Under most situations, thorough coverage of fungicide must be in place prior to secondary disease spread.  The most effective programs will start before disease appears and when products are applied at their maximum labeled rate.  Management of foliar disease may indirectly protect tubers from infection and reduce storage loss.

Early Blight

Early blight, caused by Alternaria solani, can cause serious losses in the field as well as in storage. Most general protectant fungicides used for late blight will also control early blight. Fungicides applied prior to the appearance of the first early blight lesions will provide no additional control. Proper irrigation and fertility will reduce losses due to early blight by reducing plant stress. Foliar disease severity is often not related to the degree of tuber decay. Minimize tuber bruising injury during harvest and provide optimal conditions for wound healing, in order to reduce tuber decay.

 

Product list for foliar diseases (early blight and late blight):

Product

Disease

Product per Acre

Remarks

(grouped by active ingredient)

Boscalid

 

 

 

Endura

Early Blight

 

 

 

White Mold

2.5 – 4.5 oz/A  Max of 4 times (20.5 oz) /season

 

5.5 – 10 oz/A   Max of 2 times (20 oz) /season

30 day phi

 

 

 

30 day phi

Chlorothalonil

 

 

 

Agronil 500

Late Blight,

Early Blight, Botrytis Vine Rot

1 pt, then 1 1/2 - 2 1/8 pt per acre

Apply when vines are first exposed and leaf wetness occurs.  Repeat applications at 7-10 day intervals.  May be applied through sprinkler irrigation with 10 day application interval.

Agronil 720

Late Blight,

Early Blight, Botrytis Vine Rot

¾ pt, then 1-1 ½ pt per acre

See remarks for Agronil 500

Bravo 500

Late Blight,

Early Blight, Botrytis Vine Rot

1 pt, then 1 - 2 1/8 pt per acre

Begin applications at low rate when vines are first exposed and leaf wetness occurs.  Repeat at 7-10 day intervals.  Begin at higher application rates when vines close between rows, when 18 disease severity values are reached, or when the crop reaches 300 P-days.  Increase water spray volume as canopy density increases.  May be applied through sprinkler irrigation with 10 day application interval.  Do not apply more than 23 pints per acre per growing season.

Bravo 720

Late Blight,

Early Blight, Botrytis Vine Rot

¾ pt, then 1-1 ½ pt per acre

Begin at higher application rates when vines close between rows, when 18 disease severity values are reached, or when the crop reaches 300 P-days.  May be applied through sprinkler irrigation with 10 day application intervals.  Do not apply more than 16 pints per acre per growing season.

Bravo S

(includes Sulfur)

Late Blight,

Early Blight, Botrytis Vine Rot

3-4 pt per acre;

Under dryland conditions, 2 ½-4 ¼ pt per acre (for controlling Late and Early Blight)

 

Bravo Ultrex

Late Blight,

Early Blight, Botrytis Vine Rot

0.7 lb, then 0.9-1.4 lb per acre

Higher rate when at or exceeding 18 disease Early severity values.  Do not apply more than 14.5 lbs per acre per growing season.

Bravo Weather Stik

Late Blight,

Early Blight, Botrytis Vine Rot

¾ pt, then 1-1 ½ pt per acre

Higher rate when at or exceeding 18 disease Early severity values.  Do not apply more than 16 pints per acre per growing season.

Bravo Zn

(includes Zinc)

Late Blight,

Early Blight, Botrytis Vine Rot

1 pt, then 1-2 1/8 pt per acre

Higher rate when at or exceeding 18 disease Early severity values.  Do not apply more than 23 pints per acre per growing season.

Chlorothalonil 4L

Late Blight,

Early Blight, Botrytis Vine Rot

1 pt, then 1 1/2 –2 1/8 pt per acre

 

Manicure T/O

Flowable

Late Blight,

Early Blight, Botrytis Vine Rot

1 ½ tsp/gal to cover 200 sq ft of crop

 

Terranil 6L

Late Blight,

Early Blight, Botrytis Vine Rot

¾ pt, then 1-1 ½ pt per acre

Higher rate when at or exceeding 18 disease severity values.  Do not apply more than 16 pints/acre of Terranil 6L per growing season.  Do not apply within 7 days of harvest.

Terranil Cu

(includes Copper Oxychloride)

Late Blight,

Early Blight, Botrytis Vine Rot

1.7 pt, then 2.25-3.4 pt per acre

Higher rate when at or exceeding 18 disease severity values.  Do not apply more than 36 pt per acre of Terranil Cu per growing season.  Do not apply within 7 days of harvest.

Terranil S

(includes Sulfur)

Late Blight,

Early Blight, Botrytis Vine Rot, and Powder Mildew

3-4 pt per acre; Dryland culture only (Late and Early Blight) use 2 -4 pt per acre;  4 1/3 pt per acre for Powder Mildew

 

Terranil Zn

(includes Zinc)

Late Blight,

Early Blight, Botrytis Vine Rot

1 pt, then 1-2 1/8 pt per acre

Highr rate when at or exceeding 18 disease severity values.  Do not apply more than 21 pt per acre of Terranil Zn per growing season.  Do not apply within 7 days of harvest.

Copper Hydroxide

 

 

 

Copper Flowable, 3lb.

Late Blight and Early Blight

Light disease pressure:  2/3-2 pt per acre; sever disease pressure:  2-4 pt per acre

Will also help control Colorado Potato Beetles.

Kocide 101

Late Blight and Early Blight

1-1.5 lb per ace; severe disease pressure: 3-4 lb per acre

 

Kocide 2000

Late Blight and Early Blight

0.75 to 1.25 lb per ace when plants are 6 in tall with light disease pressure; severe disease pressure 2.25 to 3 lb per acre

 

Kocide 4.5 LF

Late Blight and Early Blight

Light disease conditions 2/3-1 pt per acre;  severe disease conditions use up to 2 2/3 pt per acre

Efficacy will be improved by tank mixing with other compatible fungicides registered for use on potatoes.  Read label for tank mix partners.

Kocide DF

Late Blight and Early Blight

1-4 lb per acre

PH of spray solutions should no be below 6.5 as phytotoxicity will result.

KOP-Hydroxide 50

Late Blight and Early Blight

1-1 ½ lb per acre; severe disease pressure:  3-4 lb per acre.

 

Nu-Cop 3L

Late Blight and Early Blight

½-2 pt per acre; severe disease pressure 2-4 pt per acre

Will also suppress the Colorado Potato Beetle.

Nu-Cop 50DF

Late Blight and Early Blight

1-1.5 lb per acre; severe disease pressure 3-4 lb per acre

If  late blight is a problem, apply prior to digging or in vine kill spray.

Copper Oxychloride + Copper Sulfate, Basic

C-O-C-S Copodust

Late Blight and Early Blight

25-35 lb per acre

 

C-O-C-S WDG

Late Blight and Early Blight

1 ½-4 lb per acre

 

C-O-C-S Wettable

Late Blight and Early Blight

1 ½-4 lb per acre

 

Copper Sulfate Anhydrous

Copper-Z 4/4

Late Blight and Early Blight

31-72 fl oz per acre

 

Cymoxanil

Curzate 60DF

Late Blight

3 1/3 oz per acre

Use only with a tank mix protectant fungicide (products containing Mancozeb, Chlorothalonil, Triphenyltin Hydroxide, or Metiram)

Dicloran

 

 

 

Botran 75-W

(Dicloran)

Botrytis Blight, White Mold

2 lb per acre

Apply beginning at layby.  Continue applications at 10-14 day intervals.  May be applied up to 14 days before havrvest.

Dimethomorph

 

 

 

Acrobat MZ

(includes Mancozeb)

Late Blight

2.25 lb per acre

Note:  Approved for application in 1998 under Section 18 emergency exemptions on potatoes in 26 states where late-blight strains have shown resistance to Ridmoil fungicides.  Cyanamid notes Section 3 restriction is expected for potato.

Iprodione

 

 

 

Rovral

Early Blight

White Mold

Early Blight: 1.0-2.0 lb per acre; White Mold:  2.0 lb per acre

Do not irrigate within 24 hours of application.  Maximum of 4 applications/season.  Do not apply within 14 days of harvest.

Rovral 4 Flowable

Early Blight

White Mold

Early Blight: 1.0-2.0 pt per acre; White Mold: 2.0 pt

Do not irrigate within 24 hours of application.  Maximum of 4 applications/season.  Do not apply within 14 days of harvest.

Mancozeb

 

 

 

ManKocide

Late Blight and Early Blight

1.5-2 lb per acre; severe disease pressure 4-5 lb per acre

Do not use within 14 days of harvest.

Maneb

 

 

 

Manex

Late Blight and Early Blight

0.8-1.6 qt per acre

Do not use more than 11.2 qts/acre per season.

Mefenoxam (metalaxyl)

Ridomil Gold Bravo (includes Chlorothalonil)

Late Blight, Early Blight, and Pythium Leak

2 lb per acre

Make up to 3 applications at 14 day intervals alternating with a full rate protectant fungicide.  After which only full rate protectant fungicide applications are recommended.  Do not apply within 14 days of harvest.  You can make up to 3 applications per crop.

Ridomil Gold Copper (includes Copper Hydroxide)

Late Blight, Pink Rot, and Pythium Leak

Late Blight: tank mix of 2 lb per acre with 0.8 lb a.i./acre of maneb, mancozeb, metiram, or chlorothalonil;

Pythium rots: 2 lb per acre

Do not apply within 14 days of harvest.  You can make up to 3 applications per crop.

Ridomil Gold MZ

Late Blight, Early Blight, Pink Rot, and Pythium Leak

2.5 lb per acre

Make up to 3 applications at 14 day intervals alternation with a full rate protectant fungicide.  After which only full rate protectant fungicide applications are recommended.  Don not apply within 14 days of harvest.  You can make up to 3 applications per crop.

Ridomil Gold

Twin-Pak Bravo Liquid

Late Blight, Early Blight, Pink Rot, and Pythium Leak

Use entire container to treat 10 acres

Make up to 3 applications at 14 day intervals alternation with a full rate protectant fungicide.  After which only full rate protectant fungicide applications are recommended.  Do not apply within 14 days of harvest.  You can make up to 3 applications per crop.

Metiram

 

 

 

Polyram 80 DF

Late Blight and Early Blight

1.5-2 lb per acre

Efficacy improved with the addition of a surfactant.

Neem Oil

 

 

 

Trilogy

Early Blight, Powder Mildew.

1.0% in 25 to 100 gal per acre

 Do not exceed 2 gallons per acre.  Do not tank mix with Sulfur, Bravo/Echo and other chemically similar products.

Propamocarb

 

 

 

Tattoo C

Late Blight

2.3 pt per acre

Do not make more than 5 applications per season.  Apply at 7 to 14 day intervals with a preharvest interval of 14 days.  Note:  This product is currently not registered for general use unless your state has received a Section 18 Emergency Use label.

Sulfur

 

 

 

Cavalry

Sprayable Sulfur

Powder Mildew

3-4 lb per acre

 

Kumulus DF

Powder Mildew

3-5 lb per acre

 

Liquid Sulfur Six

Powder Mildew

3-4 pt per 8 gal of water by air

 

Microfine Sulfur

Powder Mildew and Leaf Spot

3-5 lb per acre

Will also help control the Two-Spotted Mite.

Microthiol Special

Powder Mildew

5 lb per acre

Will also help control the Two-Spotted Mite.

Sulfur 6 Flowable

Powder Mildew

3-4 pt per acre

 

Sulfur 6L

Powder Mildew

3-10 2/3 pt per acre

Will also help control the Two-Spotted Mite.

Sulfur Flowable 6

Powder Mildew

3-10 2/3 pt per acre

Will also help control the Two-Spotted Mite.

Wettable Sulfur         

Powder Mildew

5 lb per acre

Will also help control the Two-Spotted Mite.

Triphenyltin Hydroxide

Super Tin 80WP

Late Blight and Early Blight

2.5-3.75 oz per acre

Do not exceed 15 ounces per acre per season.  Do no treat within 21 days of harvest.  Will suppress the Colorado Potato Beetle.  Tank mixes with mancozeb and metiram are frequently recommended.

Quadris FL

Late Blight and Early Blight

6.2 - 15.4 fl oz

14 days.  Treat every 7 - 14 days.  Rotate with other products as indicated on label.  Maximum six applications per season.

Headline

Late Blight and Early Blight

12 fl. oz

14 days.  Treat every 7 - 14 days.  Rotate with other products as indicated on label.  Maximum six applications per season.

Gem

Late Blight and Early Blight

6-8 oz

14 days.  Treat every 7 - 14 days.  Rotate with other products as indicated on label.  Maximum six applications per season.
The information herein is supplied with the understanding that no discrimination is intended and that listing of commercial products, necessary to this guide, implies no endorsement by the authors or the Extension Services of Nebraska, Colorado, Wyoming or Montana. Criticism of products or equipment not listed is neither implied nor intended. Due to constantly changing labels, laws and regulations, the Extension Services can assume no liability for the suggested use of chemicals contained herein. Pesticides must be applied legally complying with all label directions and precautions on the pesticide container and any supplemental labeling and rules of state and federal pesticide regulatory agencies. State rules and regulations and special pesticide use allowances may vary from state to state: contact your State Department of Agriculture for the rules, regulations and allowances applicable in your state and locality.

 

 

Categories: Late blight, Early blight, Foliar fungicides, Potato, Diseases

 

Date: 09/24/2003