Disease Control

Potato - General Potato Insect Control Potato Weed Control

Common Scab (Streptomyces spp.)

Scab is caused by the soilborne bacterium Streptomyces scabies. The pathogen causes rough brown blemishes on the skins of tubers. Lesions are sometimes pitted instead of raised. The disease tends to be prevalent when soil is dry during tuber initiation, soil pH is above 5.2, and unfinished manure is used as fertilizer. Continuous cropping of potato will also increase incidence of the disease. When planting susceptible varieties, avoid fields with a history of scab. When scab is present, rotate out of potatoes for at least 2 years. Beets, carrots, radish, and some weeds can also be hosts. Maintain soil pH at 5–5.2. Irrigation scheduling may have a direct effect on the incidence of common scab during tuberization. Maintaining soil at moisture levels near field capacity during the 2–6 weeks following tuber initiation can inhibit infection. However, maintaining high soil moisture may be difficult in some soils, and it is possible that other disease problems may be aggravated by excessive irrigation. Chemical applications may be helpful but are not effective in the absence of cultural controls. Varieties with some resistance to scab include Nooksack, Russet Burbank, Dark Red, Norchip, Norland, Pike, Salem, and Superior. Allegany, Andover, Atlantic, Chieftain, Elba, Genesee, Monoma, Reba, and Redsen are moderately resistant. Several of the fingerling types also have some resistance. Katahdin, Kennebec, and Snowden are moderately susceptible. Chippewa, Kanona, Norwis, Shepody, Russet Norkotah, Defender, and Yukon Gold are some of the more susceptible lines.

FRAC Group BM02:

  • Bacillus subtilis strain QST 713 (MinuetOG): 12 to 24 oz/A (soil); PHI 0d, REI 4h.

FRAC Group M03:

  • mancozeb (Dithane F45 Rainshield): 1.6 to 2.5 fl oz/100 lb; REI 24h.

Early Blight (Alternaria solani)

Leaf spots are brown with a bulls-eye appearance and crop losses can be heavy if serious defoliation occurs before or soon after flowering. Apply any of the following fungicides when plants are 4"–6" tall. Begin applications earlier if late blight is found in your area, or if disease forecast systems recommend beginning a protection program. Repeat at 5–7 day intervals, depending on amount of moist weather or dew. Use shorter intervals under cool (60ºF–70ºF) moist conditions. Incorporate diseased vines after harvest and avoid growing pepper, tomato, and potato in a continuous rotation. Allow tubers to mature fully before harvesting, avoid harvesting when the soil is wet, and prevent mechanical injury during harvest and handling. Proper fertilization and mineral balance will reduce susceptibility of plants to early blight. Disease development, based on weather conditions near your farm, can be monitored online at the Network for Environment and Weather Applications (NEWA) website.

FRAC Group 2:

  • iprodione (Rovral 4F): 1 to 2 pt/A; PHI 14d, REI 24h. See label for crop rotation restrictions.

FRAC Group 3: 

  • azoxystrobin + difenoconazole (Quadris Top): 8 to 14 fl oz/A; PHI 14d, REI 12h, Groups 11 & 3.
  • fluopyram + prothioconazole (Luna Pro): 10 fl oz/A; PHI 14d, REI 12h, Groups 7 & 3. Do not make more than 2 applications per year.
  • mandipropamid + difenoconazole (Revus Top): 5.5 to 7 fl oz/A; PHI 14d, REI 12h, Group 40 & 3.
  • metconazole (Quash SC): 2.5 to 4 fl oz/A; PHI 1d, REI 12h.

FRAC Group 7: 

  • boscalid (Endura): 3.5 to 4.5 oz/A; PHI 10d, REI 12h. 
  • fluopyram (Velum prime): 13 fl oz/A; REI 12h. Soil treatment. Apply only once per year. 
  • fluopyram + prothioconazole (Luna Pro): 10 fl oz/A; PHI 14d, REI 12h, Groups 7 & 3. Do not make more than 2 applications per year.
  • fluopyram + pyrimethanil (Luna Tranquility): 8 to 11.2 fl oz/A; PHI 7d, REI 12h, Groups 7 & 9.
  • fluxapyroxad + pyraclostrobin (Priaxor Xemium): 4 to 8 fl oz/A; PHI 7d, REI 12h, Groups 7 & 11. The use of additives or adjuvants may improve fungicide performance in potatoes. 

FRAC Group 9: 

  • fluopyram + pyrimethanil (Luna Tranquility): 8 to 11.2 fl oz/A; PHI 7d, REI 12h, Groups 7 & 9.
  • pyrimethanil (Scala SC): 7 fl oz/A; PHI 7d, REI 12h.

FRAC Group 11:

  • azoxystrobin (Quadris F): 6 to 15.5 fl oz/A; PHI 14d, REI 4h. Do not make more than one application before alternating with fungicides from a different FRAC Group. 
  • azoxystrobin + chlorothalonil (Quadris Opti): 1.6 pt/A; PHI 14d, REI 12h, Groups 11 & M05. See label for tank mix precautions.
  • azoxystrobin + difenoconazole (Quadris Top): 8 to 14 fl oz/A; PHI 14d, REI 12h, Groups 11 & 3.
  • famoxadone + cymoxanil (Tanos): 6 oz/A; PHI 14d, REI 12h, Groups 11 & 27. Must be tank mixed with an appropriate contact fungicide from a different FRAC Group. Do not alternate or tank mix with other Group 11 fungicides.
  • fenamidone (Reason 500 SC): 5.5 to 8.2 fl oz/A; PHI 14d, REI 12h. Do not rotate with other Group 11 fungicides.
  • fluxapyroxad + pyraclostrobin (Priaxor Xemium): 4 to 8 fl oz/A; PHI 7d, REI 12h, Groups 7 & 11. The use of additives or adjuvants may improve fungicide performance in potatoes.
  • pyraclostrobin (Headline SC): 6 to 9 fl oz/A; PHI 3d, REI 12h. Do not alternate with other Group 11 fungicides.
  • trifloxystrobin (Gem 500 SC): 3 to 3.8 fl oz/A; PHI 7d, REI 12h.

FRAC Group 19: 

  • polyoxin D zinc salt (OSO 5% SCOG): 6.5 to 13 fl oz/A foliar or chemigation; PHI 0d, REI 4h. 

FRAC Group 22:

  • mancozeb + zoxamide (Gavel 75DF): 1.5 to 2 lb/A; PHI 3d, REI 48h, Groups M03 & 22. Addition of a spreading/penetrating type of adjuvant is recommended. Make no more than 2 consecutive applications before alternating with another fungicide from a different FRAC Group.

FRAC Group 27: 

  • famoxadone + cymoxanil (Tanos): 6 oz/A; PHI 14d, REI 12h, Groups 11 & 27. Must be tank mixed with an appropriate contact fungicide from a different FRAC Group. Do not alternate or tank mix with other Group 11 fungicides.

FRAC Group 28:

  • propamocarb hydrochloride (Previcur Flex): 0.7 to 1.2 pt/A; PHI 14d, REI 12h. Must be tank mixed with a contact fungicide. 

FRAC Group 40:

  • mandipropamid + difenoconazole (Revus Top): 5.5 to 7 fl oz/A; PHI 14d, REI 12h, Groups 40 & 3.

FRAC Group BM02:

  • Bacillus amyloliquefaciens strain D747 (Double Nickel 55OG): 0.25 to 3 lb/A (foliar); PHI 0d, REI 4h.

FRAC Group M01: 

  • copper hydroxide (Kocide 3000): 0.5 to 1.75 lb/A; PHI 0d, REI 48h. Do not apply in a spray solution having a pH less than 6.5 or tank mix with Aliette. An OMRI-listed formulation is available (Kocide 3000-OOG).
  • copper oxychloride + copper hydroxide (Badge X2OG): 1 to 4 lb/A; PHI 0d, REI 48h. Apply higher rate when disease is more severe. Under favorable disease conditions, can tank mix with other compatible fungicide. 

FRAC Group M03: 

  • mancozeb (Dithane F45 Rainshield): 0.4 to 1.6 qt/A; PHI 3d, REI 24h.  Use of Latron surfactant is recommended.
  • mancozeb + zoxamide (Gavel 75DF): 1.5 to 2 lb/A; PHI 3d, REI 48h, Groups M03 & 22. Addition of a spreading/penetrating type of adjuvant is recommended. Make no more than 2 consecutive applications before alternating with another fungicide from a different FRAC Group.
  • metiram (Polyram 80DF): 1.5 to 2 lb/A/100 gal water; PHI 3d, REI 24h. Use as a preventative. See label for tank-mix restrictions.

FRAC Group M05: 

  • azoxystrobin + chlorothalonil (Quadris Opti): 1.6 pt/A; PHI 14d, REI 12h, Groups 11 & M05. See label for tank-mix precautions.
  • chlorothalonil (Bravo Weather Stik): 0.75 pt/A before vines close between rows, 1 to 1.5 pt/A after vines close between rows or when disease severity values are reached; PHI 7d, REI 12h.
  • chlorothalonil + potassium phosphite (Catamaran): 4 to 5.5 pt/A; PHI 7d, REI 12h, Groups M05 & P07.

FRAC Group P06:

  • Bacillus mycoides Isolate J (LifeGard WGOG): 4.5 oz/100 gal water; PHI 0d, REI 4h.

FRAC Group P07:

  • chlorothalonil + potassium phosphite (Catamaran): 4 to 5.5 pt/A; PHI 7d, REI 12h, Groups M05 & P07.

Late Blight (Phytophthora infestans)

Symptoms of late blight often begin as irregular, water-soaked, dark spots on the lower leaves. In humid weather, the lesions expand and are often surrounded by a yellow halo. Dark lesions may also be seen on petioles and stems. Lesions may coalesce and blight entire leaves. White sporulation may be seen, especially on the edges of lesions. Lesions turn to tan or brown in drier weather. Infected tubers may have slightly depressed purple to brown lesions, and a reddish-brown rot may be seen under the skin. Late blight can occur from infected seed potatoes or infected tubers overwintered in the field. New strains of P. infestans introduced into the region are resistant to metalaxyl. Do not leave cull piles of potatoes in the field. Plant resistant varieties in well-drained soil. Avoid overhead irrigation. Remove and destroy infected plants immediately. Control volunteer potatoes and weeds, especially those in the Solanaceae family. Rotate away from solanaceous crops for at least 3 years. The fungicides used for early blight have some protective ability against Phytophthora but cannot be relied on to provide significant control. If late blight is reported within 0.5 miles, begin applications of an appropriate fungicide. Disease progression throughout the US can also be monitored at www.usablight.org. Disease development predictions based on weather conditions near your farm can be monitored on-line at the Network for Environment and Weather Applications (NEWA) website. 

FRAC Group 3: 

  • mandipropamid + difenoconazole (Revus Top): 5.5 to 7 fl oz/A; PHI 14d, REI 12h, Groups 40 & 3. Addition of a spreading/penetrating type of adjuvant is recommended. 

FRAC Group 4:

  • mefenoxam + chlorothalonil (Ridomil Gold Bravo SC): 2.5 pt/A; PHI 14d, REI 48h, Groups 4 & M05. 
  • mefenoxam + copper hydroxide (Ridomil Gold Copper): 2 lb/A; PHI 14d, REI 48h, Groups 4 & M01. Do not plant any crop which is not registered for use with Ridomil Gold active ingredient in treated soil for a period of 12 months.
  • mefenoxam + mancozeb (Ridomil Gold MZ): 2.5 lb/A; PHI 3d, REI 48h, Groups 4 & M03. Do not plant any crop which is not registered for use with Ridomil Gold active ingredient in treated soil for a period of 12 months.

FRAC Group 11:

  • azoxystrobin + chlorothalonil (Quadris Opti): 1.6 pt/A; PHI 14d, REI 12h, Groups 11 & M05. See label for tank mix precautions.
  • famoxadone + cymoxanil (Tanos): 6 to 8 oz/A; PHI 14d, REI 12h, Groups 11 & 27. Must be tank mixed with an appropriate contact fungicide from a different FRAC Group. Do not alternate or tank mix with other Group 11 fungicides.
  • fenamidone (Reason 500 SC): 5.5 to 8.2 fl oz/A; PHI 14d, REI 12h. Do not make more than 1 application before alternating to a fungicide from a different FRAC Group.
  • pyraclostrobin (Headline SC): 6 to 12 fl oz/A; PHI 3d, REI 12h. Do not rotate with other Group 11 fungicides.
  • trifloxystrobin (Gem 500 SC): 3.8 fl oz/A; PHI 7d, REI 12 h. Must be tank mixed with a protectant.

FRAC Group 21: 

  • cyazofamid (Ranman 400SC): 1.4 to 2.75 fl oz/A; PHI 7d, REI 12h. Do not make more than 1 application before alternating with a fungicide with a different mode of action. Addition of an organosilicon surfactant may be desirable.

FRAC Group 22: 

  • mancozeb + zoxamide (Gavel 75DF): 1.5 to 2 lb/A; PHI 3d, REI 48h, Group M03 & 22. Increase the use rate according to vine development.
  • zoxamide + chlorothalonil (Zing!): 30 to 34 fl oz/A; PHI 7d, REI 12h, Groups 22 & M05.

FRAC Group 27: 

  • cymoxanil (Curzate 60 DF): 3.2 oz/A; PHI 14d, REI 12h. Use only in combination with a labeled rate of a protectant such as manzate, chlorothalonil, or triphenyltin hydroxide.
  • cymoxanil + chlorothalonil (ECHO 459/Cymoxanil 61 aka Ariston): 2 pt/A; PHI 14d, REI 12h, Groups 27 & M05. Must be applied in a tank mix with a fungicide from a different FRAC Group. 
  • famoxadone + cymoxanil (Tanos): 6 to 8 oz/A; PHI 14d, REI 12h, Groups 11 & 27. Must be tank mixed with an appropriate contact fungicide from a different FRAC Group. Do not alternate or tank mix with other Group 11 fungicides.

FRAC Group 28: 

  • propamocarb hydrochloride (Previcur Flex): 0.7 to 1.2 pt/A; PHI 14d, REI 12h. Must be tank mixed with a contact fungicide. 

FRAC Group 29:

  • fluazinam (Omega 500F): 5.5 fl oz/A; PHI 14d, REI 12h. Must be applied in a tank mix with a fungicide from a different FRAC Group. 

FRAC Group 40: 

  • dimethomorph (Forum): 4 to 6 fl oz/A; PHI 4d, REI 12h. Must be applied in a tank mix with a fungicide from a different FRAC Group. 
  • mandipropamid + difenoconazole (Revus Top): 5.5 to 7 fl oz/A; PHI 14d, REI 12h, Groups 40 & 3. Addition of a spreading/penetrating type of adjuvant is recommended. 
  • oxathiapiprolin + mandipropamid (Orondis Ultra): 5.5 to 8 fl oz/A; PHI 14d, REI 4h, Groups 49 & 40.

FRAC Group 45:

  • ametoctradin + dimethomorph (Zampro): 11 to 14 fl oz/A; PHI 4d, REI 12h, Groups 45 & 40. Do not make more than 2 applications before alternating to a labeled fungicide from a different FRAC Group.

FRAC Group 49: 

  • oxathiapiprolin + chlorothalonil (Orondis Opti): 1.75 to 2.7 pt/A; PHI 7d, REI 12h, Groups 49 & M05. 
  • oxathiapiprolin + mandipropamid (Orondis Ultra): 5.5 to 8 fl oz/A; PHI 14d, REI 4h, Groups 49 & 40. 

FRAC Group BM02:

  • Bacillus amyloliquefaciens strain D747 (Double Nickel 55OG): 0.25 to 3 lb/A (foliar); PHI 0d, REI 4h.

FRAC Group M01:

  • copper hydroxide (Kocide 3000): 0.5 to 1.75 pt/A; PHI 0d, REI 48h. Do not apply in a spray solution having a pH less than 6.5 or tank mix with Aliette. An OMRI-listed formulation is available (Kocide 3000-OOG).
  • copper oxychloride + copper hydroxide (Badge SC): 1 to 4 lb/A; PHI 0d, REI 48h. Apply up to 4lb/A when disease is more severe. Under favorable disease conditions, can tank mix with other compatible fungicide.
  • mefenoxam + copper hydroxide (Ridomil Gold Copper): 2 lb/A; PHI 14d, REI 48h, Groups 4 & M01. Do not plant any crop that is not registered for use with Ridomil Gold active ingredient in treated soil for a period of 12 months.

FRAC Group M03: 

  • mancozeb (Dithane F45 Rainshield): 0.4 to 1.6 qt/A; PHI 3d, REI 24h.
  • mancozeb + zoxamide (Gavel 75DF): 1.5 to 2 lb/A; PHI 3d, REI 48h, Groups M03 & 22. Increase the use rate according to vine development.
  • mefenoxam + mancozeb (Ridomil Gold MZ): 2.5 lb/A; PHI 3d, REI 48h, Groups 4 & M03. Do not plant any crop which is not registered for use with Ridomil Gold active ingredient in treated soil for a period of 12 months.

FRAC Group M05:

  • azoxystrobin + chlorothalonil (Quadris Opti): 1.6 pt/A; PHI 14d, REI 12h, Groups 11 & M05. See label for tank mix precautions.
  • chlorothalonil (Bravo Weather Stik): 0.75 pt/A before vines close between rows, 1 to 1.5 pt/A after vines close between rows or when disease severity values are reached; PHI 7d, REI 12h.
  • chlorothalonil + potassium phosphite (Catamaran): 4 to 5.5 pt/A; PHI 7d, REI 12h, Groups M05 & P07. Do not apply in a solution having a pH of less than 6.5. See label for tank mix restrictions.
  • cymoxanil + chlorothalonil (ECHO 459, aka Ariston): 2 pt/A; PHI 14d, REI 12h, Groups 27 & M05. Must be applied in a tank mix with a fungicide from a different FRAC Group.
  • mefenoxam + chlorothalonil (Ridomil Gold Bravo SC): 2.5 pt/A; PHI 14d, REI 48h, Groups 4 & M05.
  • oxathiapiprolin + chlorothalonil (Orondis Opti): 1.75 to 2.7 pt/A; PHI 7d, REI 12h, Groups 49 & M05. 
  • zoxamide + chlorothalonil (Zing!): 30 to 34 fl oz/A; PHI 7d, REI 12h, Groups 22 & M05.

FRAC Group P06:

  • Bacillus mycoides Isolate J (LifeGard LCOG): 1 gal/100.0 gal water; PHI 0d, REI 4h. Apply in an alternating or tank mix program with labeled fungicides. 

FRAC Group P07:

  • chlorothalonil + potassium phosphite (Catamaran): 4 to 5.5 pt/A; PHI 7d, REI 12h, Groups M05 & P07. Do not apply in a solution having a pH of less than 6.5. See label for tank mix restrictions.
  • phosphorus acid (Fosphite): 3 to 5 qt/10 to 20 gal water; PHI 0d, REI 4h. Do not apply to heat- or moisture-stressed plants. 

Potato Leaf Roll Virus (PLRV)

Potato leafroll virus is the most serious virus disease of potatoes in New England and can result in significant yield reductions. The virus is transmitted by aphids in a persistent manner (i.e., they carry the virus for extended periods). The virus can overwinter in unharvested tubers which may develop into virus-infected volunteer plants. Purchase certified seed to limit viruses. Consult seed producers to determine what the certification covers. Destroy cull piles and volunteer plants. Rogue plants with virus symptoms. When populations of aphids reach economic thresholds, treatment is warranted. Do not use any of last year's potato harvest for seed.

Potato Viruses S (PVS), A (PVA), and X (PVX)

These viruses may occur singly or in combination. PVY, PVS, and PVA are spread by aphids in a nonpersistent manner. PVX is not known to be spread by aphids but is easily spread by plant-to-plant contact, farm machinery, or cultural practices. Purchase certified seed to limit viruses. Consult seed producers to determine what the certification covers. Destroy cull piles and volunteer plants. Do not keep potatoes for seed. Plant early, use resistant varieties, and control aphid populations.

Potato Virus Y (PVY)

PVY has a worldwide distribution and is one of the most important viruses affecting potato. Three main strains have been described that differ in distribution and symptomatology. Symptoms vary widely with cultivars and virus strain combinations, ranging from mild mosaic to severe foliar necrosis. One strain can cause a symptomless current season infection that leads to next-generation infection. Primary symptoms of PVY include mottling, yellowing, leaf drop, and premature plant death. Potato with secondary infection exhibit stunting, mottling, stem necrosis, and crinkled leaves. Symptoms may be suppressed by low or elevated temperatures. Tuber symptoms generally correspond to leaf effects. PVY is the type member of the plant virus family Potyviridae, the largest and most significant virus group, and has caused significant losses in agricultural, forage, and horticultural crops. Hosts include solanaceous crops, legumes, and crops in the spinach/chard/beet family. Infection is transmitted in a non-persistent manner (characterized by very short acquisition and inoculation times of seconds to minutes) by more than 25 species of aphids and may also occur mechanically by foliar or tuber contact. Long distance transport is by winged aphids and infected seed pieces. Use certified, disease-free seed tubers to reduce primary inoculum. Insecticides may slow the spread of disease within a crop but may actually increase insect probing and be counterproductive because only a few seconds of insect feeding is sufficient for virus transmission. Minimize contact disease spread by minimizing mechanical damage during cultivation, spraying, and harvest. Sanitize seed cutting equipment between seed lots. Remove virus-infected plants. Plant resistant varieties: Villeta Rose, Eva, Rio, Grande Russet, and Premier Russet.

Pythium Leak or Shell Rot (Pythium spp.)

Leak can be a problem with stored potatoes, especially bruised, immature potatoes harvested in hot weather. Symptoms include spongy, wet internal rot of tubers with diseased flesh separated from healthy tissue by a dark boundary line. In advanced infections, hollow cavities form and all that remains of some infected tubers are tuber shells with thin papery skins.

FRAC Group 4:

  • mefenoxam (Ridomil Gold SL): 0.42 oz/1,000 linear ft in-furrow; PHI 14d, REI 48h. Apply as a 6"–8" band at planting in a minimum of 3 gallons of water. See label for pre-plant incorporated application rates and restrictions. It can be supplemented with a phosphorous acid product. Do not plant any crop which is not registered for use with Ridomil Gold active ingredient in treated soil for a period of 12 months.
  • mefenoxam + chlorothalonil (Ridomil Gold Bravo SC): 2.5 pt/A; PHI 14d, REI 48h, Groups 4 & M05. 
  • mefenoxam + copper hydroxide (Ridomil Gold Copper): 2 lb/A; foliar applied. PHI 14d, REI 48h, Groups 4 & M01. 
  • mefenoxam + mancozeb (Ridomil Gold MZ WG): 2.5 lb/A; PHI 3d, REI 48h, Groups 4 & M03. 

FRAC Group M01:

  • mefenoxam + copper hydroxide (Ridomil Gold Copper): 2 lb/A; foliar applied. PHI 14d, REI 48h, Groups 4 & M01.

FRAC Group M03:

  •  mefenoxam + mancozeb (Ridomil Gold MZ WG): 2.5 lb/A; PHI 3d, REI 48h, Groups 4 & M03. 

FRAC Group M05:

  • mefenoxam + chlorothalonil (Ridomil Gold Bravo SC): 2.5 pt/A; PHI 14d, REI 48h, Groups 4 & M05. 

FRAC Group P07:

  • phosphorus acid (Phostrol): 3.75 to 10 pt/A in-furrow, 2.5 to 10 pt/A foliar; PHI 0d, REI 4h, Group P07. For suppression of leak, combine the in-furrow treatment of phosphorous acid with a mefenoxam fungicide (Group 4). Additional in-season foliar applications of a phosphorous acid-containing fungicide tank mixed with a mefenoxam-containing fungicide may be necessary to achieve adequate control. 

Seed Piece Fungicide Treatment

Potato seed treatment is one of the more overlooked portions of a whole-season disease control program. Properly suberized and properly treated seed will provide a healthier, more uniform stand of plants. Proper application of the appropriate material is necessary. Improper applications may prove phytotoxic. Inadequate coverage may not totally protect the seed-piece. Dust formulations are preferable for cut seed. Dip treatments may spread bacteria to seed pieces that were previously not affected. Many seed treatments are now formulated with Douglas fir or alder bark as a carrier; improved healing of the cut surface has been reported with these products. Some seed treatments can be purchased combined with imidacloprid. Do not use treated seed potatoes for feed or food purposes. 

FRAC Group 4: 

  • azoxystrobin + mefenoxam (Quadris Ridomil Gold SL): 0.82 fl oz/1000 row feet; PHI 0d, REI 0h, Groups 11 & 4.

FRAC Group 7: 

  • fluopyram (Velum Prime): 13 fl oz/A; PHI 0d,REI 12h. Soil application. Apply only once per year. 

FRAC Group 11:

  • azoxystrobin + mefenoxam (Quadris Ridomil Gold SL): 0.82 fl oz/1000 row feet; PHI 0d, REI 0h, Groups 11 & 4.
  • fenamidone (Reason 500 SC): 0.15 fl oz/100 lb seed pieces; PHI 14d, REI 12h. For seedborne late blight. 

FRAC Group 12:

  • fludioxonil (Maxim PSP): 0.5 lb/100 lb seed pieces; PHI 0d, REI 12h. Apply to cover thoroughly. REI may be reduced; see label for details.
  • fludioxonil + mancozeb (Maxim MZ): 0.5 lb/100 lb; PHI 0d, REI 24h, Groups 12 & M03.

FRAC Group 14: 

  • PCNB (Turfcide 4F, aka Blocker 4F or TerraClor 400): 5.2 to 10 fl oz/1000 row ft; PHI 0d, REI 12h. For common scab and stem canker/black scurf. 

FRAC Group 27: 

  • cymoxanil (Curzate 60 DF): 0.25 oz/100 lb seed pieces; REI 12h. For seedborne late blight. Must be applied in a tank mix with another registered product.

FRAC Group BM02:

  • Bacillus subtilis strain ENV503 (Companion MaxxOG): 2 oz/100 lb seed pieces; PHI 0d, REI 4h. For seed cuttings dip. 
  • Trichoderma harzianum Rifai Strain T-22 (RootShield WPOG): 0.02 to 3 oz/100 lb seed pieces; PHI 0d, REI 4h.May be applied with compatible chemical seed dusts.
  • Trichoderma harzianum Rifai strain T-22 + T. virens Strain G-41 (Rootshield PlusOG): 0.03 to 3 lb/100 lb seed (dust), 0.25 to 1.5 lb/20 gal (dip); PHI 0d, REI 4h. Labeled for plant root pathogens. Not effective in cool (below 50°F) and wet soils. 

FRAC Group M03:

  • fludioxonil + mancozeb (Maxim MZ): 0.5 lb/100 lb; PHI 0d, REI 24h, Groups 12 & M03.
  • mancozeb (Dithane F45 Rainshield): 1.6 to 2.5 fl oz/100 lb; REI 24h.

Soft Rot/Black Leg (Dickeya and Pectobacterium spp.)

Dickeya and Pectobacterium are bacterial pathogens. In general, these species are transmitted via seed pieces. Infected seed potatoes are usually non-symptomatic or have non-distinctive rot symptoms. Use sound sanitation practices when handling seed pieces to prevent contamination of other potato lots. The first symptom is poor emergence (skips in a production field) due to rotting seed pieces. Plants that emerge from contaminated seed often wilt and may have blackened stems that extend upwards from the rotting seed piece. Some affected plants may only appear unthrifty. The internal stem tissue may be discolored. Rotations that include corn followed by brassicas should be avoided prior to planting potatoes. Growers should ensure that they purchase certified seed that has been inspected for Dickeya/Pectobacterium. Fields where these pathogens have been confirmed should be avoided for the following year. No pesticides are effective.

Verticillium and Fusarium Wilts

Verticillium and Fusarium are soil-borne fungi that cause vascular wilts of potato. They can be introduced into fields by contaminated seed or soil. Symptoms of vascular wilts in the field include yellowing and withering leaves, beginning at the bottom of the plant, and progressing upward. Wilting is most often observed on hot, sunny days. Brown discoloration of vascular tissue may be seen in stems at or just above the soil line. Plants may be seen to wilt on one side but not the other. Fusarium may also cause stunting. 

Continual potato production tends to result in an increase in wilt disease. A combination of lesion nematodes and Verticillium results in early plant death. Rotation with non-susceptible crops such as grasses will reduce disease. Destruction of infected potato vines by tillage encourages rapid decomposition and lessens the build-up of soil inoculum. At this time, there are no varieties resistant to Fusarium wilt. Avoid highly susceptible cultivars and start with certified, disease-free seed pieces.

FRAC Group 22:

  • ethaboxam (Elumin): 8 fl oz/A; PHI N/A, REI 12h. Make in-furrow or sidedress applications. Do not make more than 2 applications per year. 

FRAC Group BM02:

  • Bacillus subtilis strain QST 713 (MinuetOG): 2 to 24 oz/A (soil); PHI 0d, REI 4h.

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New England Vegetable Management Guide