Disease Control : New England Vegetable Management Guide : UMass Amherst

Onion, Scallion, and Shallot - General Onion, Scallion & Shallot Insect Control Onion, Scallion & Shallot Weed Control

Botrytis Leaf Blight (Botrytis squamosa)

Avoid close planting and orient rows in the direction of prevailing winds. Plant in well-drained soil. Remove or plow under crop debris after harvest. Remove cull piles and practice crop rotation. Avoid excessive nitrogen fertilization as this increases leaf canopies and disease susceptibility. Plant less susceptible cultivars when available. Irrigate early in the day to reduce leaf wetness periods. Incorporate crop residues after harvest. Apply fungicides based on a disease forecast system (e.g., BOTCAST). Disease development, based on weather conditions near your farm, can be monitored online at the Network for Environment and Weather Applications (NEWA).

For dry bulb onions:

FRAC Group 2:

iprodione (Rovral 4F): 1.5 pt/A (alone), 1 pt/A (tank-mix); PHI 7d, REI 24h. Dry bulb only.

FRAC Group 3:

azoxystrobin + difenoconazole (Quadris Top): 12 to 14 fl oz/A; PHI 7d, REI 12h, Groups 11 & 3.
azoxystrobin + propiconazole (Quilt Xcel): 17.5 to 21 fl oz/A; PHI 14d, REI 12h, Groups 11 & 3.
difenoconazole + cyprodinil (Inspire Super): 14 to 20 fl oz/A; PHI 7d, REI 12h, Group 3 & 9.
propiconazole (Tilt): 4 to 8 oz/A (alone), 2 to 4 oz/A (tank-mix); PHI 14d, REI 12. Suppression only.

FRAC Group 7:

boscalid (Endura): 6.8 oz/A; PHI 7d, REI 12h. Apply in-furrow.
fluopyram + pyrimethanil (Luna Tranquility): 16 to 27 fl oz/A; PHI 7d, REI 12h, Groups 7 & 9. Do not make more than 2 sequential applications before alternating with a non-Group 7 or 9 fungicide.
fluxapyroxad + pyraclostrobin (Merivon Xemium): 8 to 11 fl oz/A; PHI 7d, REI 12, Groups 7 & 11. Use preventively.
penthiopyrad (Fontelis): 16 to 24 oz/A; PHI 3d, REI 12h.
pyraclostrobin + boscalid (Pristine): 14.5 to 18.5 oz/A; PHI 7d, REI 12h, Groups 11 & 7. Do not make more than 2 applications before alternating with a fungicide from a different FRAC Group.

FRAC Group 9:

cyprodinil (Vangard WG): 10 oz/A; PHI 7d, REI 12h.
cyprodinil + fludioxonil (Switch 62.5 WG): 11 to 14 oz/A; PHI 7d, REI 12h, Groups 9 & 12.
difenoconazole + cyprodinil (Inspire Super): 14 to 20 fl oz/A; PHI 7d, REI 12h, Group 3 & 9.
fluopyram + pyrimethanil (Luna Tranquility): 16 to 27 fl oz/A; PHI 7d, REI 12h, Groups 7 & 9. Do not make more than 2 applications before alternating with a non-Group 7 or 9 fungicide.
pyrimethanil (Scala SC): 18 fl oz/A (alone), 9 to 18 fl oz/A (tank-mix); PHI 7d, REI 12h.

FRAC Group 11:

azoxystrobin (Quadris F): 9 to 15.5 fl oz/A; PHI 0d, REI 4h.
azoxystrobin + chlorothalonil (Quadris Opti): 1.6 to 3.2 pt/A; PHI 7d, REI 12h, Groups 11 & M05.
azoxystrobin + difenoconazole (Quadris Top): 12 to 14 fl oz/A; PHI 7d, REI 12h, Groups 11 & 3.
azoxystrobin + propiconazole (Quilt Xcel): 17.5 to 21 fl oz/A; PHI 14d, REI 12h, Groups 11 & 3.
fluxapyroxad + pyraclostrobin (Merivon Xemium): 8 to 11 fl oz/A; PHI 7d, REI 12, Groups 7 & 11. Use preventively.
pyraclostrobin (Cabrio EG): 12 oz/A; PHI 7d, REI 12h. For suppression only. Do not rotate with other Group 11 fungicides.
pyraclostrobin + boscalid (Pristine): 14.5 to 18.5 oz/A; PHI 7d, REI 12h, Groups 11 & 7. Do not make more than 2 applications before alternating with a fungicide from a different FRAC Group.

FRAC Group 12:

cyprodinil + fludioxonil (Switch 62.5 WG): 11 to 14 oz/A; PHI 7d, REI 12h, Groups 9 & 12.

FRAC Group 19:

polyoxin D zinc salt (VEGGIETURBO 5SC^OG): 6.5 to 13 fl oz/A; PHI 0d, REI 4h.

FRAC Group 29:

fluazinam (Omega 500F): 16 fl oz/A; PHI 7d, REI 12h to 24h (hand weeding).

FRAC Group M03:

mancozeb (Dithane F45): 2.4 qt/A; PHI 7d, REI 24h. Dry bulb only.

FRAC Group M05:

azoxystrobin + chlorothalonil (Quadris Opti): 1.6 to 3.2 pt/A; PHI 7d, REI 12h, Groups 11 & M05.
chlorothalonil (Bravo Weather Stik): 1 to 3 pt/A; PHI 7d, REI 12h. To suppress Botrytis neck rot in storage, a minimum of 3 weekly applications prior to lifting using 1.25 to 1.8 lb/A is recommended.
potassium phosphite + chlorothalonil (Catamaran): 4 to 7 pt/A; PHI 7d (dry bulb), 14d (green), REI 12, Groups P07 & M05.

FRAC Group P07:

potassium phosphite + chlorothalonil (Catamaran): 4 to 7 pt/A; PHI 7d (dry bulb), 14d (green), REI 12, Groups P07 & M05.

For green onions and shallots:

FRAC Group 3:

azoxystrobin + difenoconazole (Quadris Top): 12 to 14 fl oz/A; PHI 7d, REI 12h, Groups 11 & 3.
azoxystrobin + propiconazole (Quilt Xcel): 17.5 to 21 fl oz/A; PHI 0d, REI 12h, Groups 11 & 3.
difenoconazole + cyprodinil (Inspire Super): 14 to 20 fl oz/A; PHI 14d, REI 12h, Group 3 & 9.
propiconazole (Tilt): 4 to 8 oz/A (alone), 2 to 4 oz/A (tank-mix); PHI 14d, REI 12. Suppression only.

FRAC Group 7:

boscalid (Endura): 6.8 oz/A; PHI 7d, REI 12h. Apply in-furrow.
fluopyram + pyrimethanil (Luna Tranquility): 16 to 27 fl oz/A; PHI 7d, REI 12h, Groups 7 & 9.
fluxapyroxad + pyraclostrobin (Merivon Xemium): 8 to 11 fl oz/A; PHI 7d, REI 12, Groups 7 & 11. Use preventively.
penthiopyrad (Fontelis): 16 to 24 oz/A; PHI 3d, REI 12h.
pyraclostrobin + boscalid (Pristine): 14.5 to 18.5 oz/A; PHI 7d, REI 12h, Groups 11 & 7.

FRAC Group 9:

cyprodinil (Vangard WG): 10 oz/A; PHI 7d, REI 12h.
cyprodinil + fludioxonil (Switch 62.5 WDG): 11 to 14 oz/A; PHI 7d, REI 12h, Groups 9 & 12.
difenoconazole + cyprodinil (Inspire Super): 14 to 20 fl oz/A; PHI 14d, REI 12h, Group 3 & 9.
fluopyram + pyrimethanil (Luna Tranquility): 16 to 27 fl oz/A; PHI 7d, REI 12h, Groups 7 & 9.
pyrimethanil (Scala SC): 18 fl oz/A (alone), 9 to 18 fl oz/A (tank-mix); PHI 7d, REI 12h.

FRAC Group 11:

azoxystrobin (Quadris F): 9 to 15.5 fl oz/A; PHI 0d, REI 4h.
azoxystrobin + chlorothalonil (Quadris Opti): 1.6 to 3.2 pt/A; PHI 14d, REI 12h, Groups 11 & M05. See label for tank mix precautions.
azoxystrobin + difenoconazole (Quadris Top): 12 to 14 fl oz/A; PHI 7d, REI 12h, Groups 11 & 3.
azoxystrobin + propiconazole (Quilt Xcel): 17.5 to 21 fl oz/A; PHI 0d, REI 12h, Groups 11 & 3.
fluxapyroxad + pyraclostrobin (Merivon Xemium): 8 to 11 fl oz/A; PHI 7d, REI 12, Groups 7 & 11. Use preventively.
pyraclostrobin + boscalid (Pristine): 14.5 to 18.5 oz/A; PHI 7d, REI 12h, Groups 11 & 7.

FRAC Group 12:

cyprodinil + fludioxonil (Switch 62.5 WDG): 11 to 14 oz/A; PHI 7d, REI 12h, Groups 9 & 12.

FRAC Group 19:

polyoxin D zinc salt (Oso 5%SC^OG): 6.5 to 13 fl oz/A; PHI 0d, REI 4h.

FRAC Group M05:

azoxystrobin + chlorothalonil (Quadris Opti): 1.6 to 3.2 pt/A; PHI 14d, REI 12h, Groups 11 & M05. See label for tank mix precautions.
chlorothalonil (Bravo Weather Stik): 1.5 to 3 pt/A; PHI 14d, REI 12h. When disease is present, use the higher rate.
potassium phosphite + chlorothalonil (Catamaran): 4 to 7 pt/A; PHI 7d (dry bulb), 14d (green), REI 12, Groups P07 & M05.

FRAC Group P07:

potassium phosphite + chlorothalonil (Catamaran): 4 to 7 pt/A; PHI 7d (dry bulb), 14d (green), REI 12, Groups P07 & M05.

Botrytis Neck Rot (Botrytis allii and B. aclada)

Botrytis allii and Botrytis aclada cause neck rot of onion. These are distinct from Botrytis porri which causes neck rot of garlic and leeks. Infection occurs in the field in periods of prolonged moist, cool weather. Symptoms primarily appear in storage. Necks appear soft and water-soaked, eventually turning brown. Gray, fuzzy sporulation and small, black sclerotia form in diseased tissues.

Do not apply nitrogen late in the season and avoid high-density planting. Undercut bulbs to promote drying. Allow the tops to dry completely and have tight necks before topping. Avoid condensation on bulbs during storage. Maintain storage environment at 32°F–33°F and 70%–75% relative humidity. Fungicides applied to control Botrytis leaf blight may also decrease neck rot.

FRAC Group 2:

iprodione (Rovral 4F): 1.5 pt/A (alone), 1 pt/A (tank-mix); PHI 7d, REI 24h. Dry bulb only.

FRAC Group 7:

fluxapyroxad + pyraclostrobin (Merivon Xemium): 8 to 11 fl oz/A; PHI 7d, REI 12, Groups 7 & 11. Use preventively.
pyraclostrobin + boscalid (Pristine): 14.5 to 18.5 oz/A; PHI 7d, REI 12h, Groups 11 & 7.

FRAC Group 9:

cyprodinil + fludioxonil (Switch 6.25 WG): 11 to 14 oz/A; PHI 7d, REI 12h, Groups 9 & 12. Suppression only.
pyrimethanil (Scala SC): 18 fl oz/A (alone), 9 to 18 fl oz/A (tank-mix); PHI 7d, REI 12h.

FRAC Group 11:

azoxystrobin + chlorothalonil (Quadris Opti): 1.6 to 3.2 pt/A; PHI 14d, REI 14h, Groups 11 & M05. Suppression only. See label for tank mix precautions.
fluxapyroxad + pyraclostrobin (Merivon Xemium): 8 to 11 fl oz/A; PHI 7d, REI 12, Groups 7 & 11. Use preventively.
pyraclostrobin + boscalid (Pristine): 14.5 to 18.5 oz/A; PHI 7d, REI 12h, Groups 11 & 7.

FRAC Group 12:

cyprodinil + fludioxonil (Switch 6.25 WG): 11 to 14 oz/A; PHI 7d, REI 12h, Groups 9 & 12. Suppression only.

FRAC Group 19:

polyoxin D zinc salt (Oso 5% SC^OG): 3.75 to 13 fl oz/A; PHI 0d, REI 4h.

FRAC Group 29:

fluazinam (Omega 500F): 16 fl oz/A; PHI 7d, REI 12h, 24h (hand weeding).

FRAC Group M03:

mancozeb (Dithane M45): 3 qt/A; PHI 7d, REI 24h. Dry bulb only.

FRAC Group M05:

azoxystrobin + chlorothalonil (Quadris Opti): 1.6 to 3.2 pt/A; PHI 14d, REI 14h, Groups 11 & M05. Suppression only. See label for tank mix precautions.

Downy Mildew (Peronospora destructor)

Downy mildew of allium crops is caused by a fungus-like pathogen that overwinters in infected bulbs, seeds, or sets. It can also persist in wild Alliums, cull piles, and in fall-seeded onion. Only a few spores are needed to initiate an epidemic. During extended periods of cool, humid weather, this disease can be highly destructive, causing losses in both yield and bulb quality. Symptoms can be seen as a fuzzy grayish-purple growth on the surface of leaves. Affected leaves may turn yellow and brown.

Eliminate cull piles, volunteer onion plants, and wild Allium species. Practice a 3- to 4-year rotation. Plant in well-drained soil and orient rows in the same direction as prevailing winds. Use drip irrigation or irrigate early in the day to enable rapid drying of foliage. A regular program of fungicide spraying based on climatic conditions and disease forecasts should be followed. Apply fungicides when mildew is present in the area and weather favors disease increase based upon a disease forecasting system (i.e., DOWNCAST). Disease development, based on weather conditions near your farm, can be monitored online at the Network for Environment and Weather Applications (NEWA).

For dry bulb onions:

FRAC Group 4:

mefenoxam + chlorothalonil (Ridomil Gold Bravo SC): 2.5 pt/A; PHI 7d, REI 48h, Groups 4 & M05.
mefenoxam + copper hydroxide (Ridomil Gold Copper): 2 lb/A; PHI 10d, REI 48h, Groups 4 & M01.
mefenoxam + mancozeb (Ridomil Gold MZ): 2.5 lb/A; PHI 7d, REI 48h, Groups 4 & M03. Thorough coverage is needed. Do not apply to exposed bulbs.

FRAC Group 7:

fluxapyroxad + pyraclostrobin (Merivon Xemium): 8 to 11 fl oz/A; PHI 7d, REI 12, Groups 7 & 11. Use preventively. For suppression only.
pyraclostrobin + boscalid (Pristine): 18.5 oz/A; PHI 7d, REI 12h, Groups 7 & 11. Suppression only. Rotate with a downy mildew fungicide from a different FRAC Group.
salts of phosphorous acid (Fosphite): 1 to 2 qt/50 gal; PHI 0d, REI 4h. Do not apply to heat- or moisture-stressed plants or to plants recently treated with copper.

FRAC Group 11:

azoxystrobin (Quadris F): 9 to 15.5 fl oz/A; PHI 0d, REI 4h.
azoxystrobin + chlorothalonil (Quadris Opti): 2.4 to 3.6 pt/A; PHI 7d, REI 12h, Groups 11 & M05. See label for tank mix precautions.
famoxadone + cymoxanil (Tanos): 8 fl oz/A; PHI 3d, 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 fl oz/A; PHI 7d, REI 12h. Do not make more than 1 application before alternating to a non-Group 11 fungicide.
fluxapyroxad + pyraclostrobin (Merivon Xemium): 8 to 11 fl oz/A; PHI 7d, REI 12, Groups 7 & 11. Use preventively. For suppression only.
pyraclostrobin (Cabrio EG): 12 oz/A; PHI 7d, REI 12h. Do not rotate with other Group 11 fungicides.
pyraclostrobin + boscalid (Pristine): 18.5 oz/A; PHI 7d, REI 12h, Groups 7 & 11. Suppression only. Rotate with a downy mildew fungicide from a different FRAC Group.

FRAC Group 19:

polyoxin D zinc salt (Oso 5%SC^OG): 6.5 to 13 fl oz/A; PHI 0d, REI 4h.

FRAC Group 21:

cyazofamid (Ranman 400 SC): 2.75 to 3 fl oz/A; PHI 0d, REI 12h.

FRAC Group 22:

zoxamide + chlorothalonil (Zing!): 30 fl oz/A; PHI 7d, REI 12h, Groups 22 & M05. Do not apply to exposed bulbs.
zoxamide + mancozeb (Gavel 75 DF): 1.5 to 2 lb/A; PHI 7d, REI 48h, Groups 22 & M03. Do not apply to exposed bulbs.

FRAC Group 27:

famoxadone + cymoxanil (Tanos): 8 fl oz/A; PHI 3d, 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 29:

fluazinam (Omega 500F): 16 fl oz/A; PHI 7d, REI 12h, 24h (hand weeding).

FRAC Group 40:

ametoctradin + dimethomorph (Zampro): 14 fl oz/A; PHI 0d, REI 12h, Groups 45 & 40.
mandipropamid (Revus): 5.5 to 8 fl oz/A; PHI 7d, REI 4h. A silicone-based adjuvant must be added at recommended rates.

FRAC Group 45:

ametoctradin + dimethomorph (Zampro): 14 fl oz/A; PHI 0d, REI 12h, Groups 45 & 40.
dimethomorph (Forum): 6 fl oz/A; PHI 0d, REI 12h.

FRAC Group 49:

oxathiapiprolin + chlorothalonil (Orondis Opti): 1.75 to 5 pt/A; PHI 7d, REI 12h, Groups 49 & M05.
oxathiapiprolin (Orondis Opti A): 2 to 4.8 fl oz/A; PHI 0d, REI 4h. Do not exceed more than 6 applications per acre per year.

FRAC Group M01:

copper hydroxide (Kocide 3000): 0.75 to 1.5 lb/A; PHI 0d, REI 48h. Can cause phytotoxicity to leaves. 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-O^OG).
mancozeb + copper hydroxide (ManKocide): 2.5 lb/A; PHI 7d, REI 48h, Groups M03 & M01. Dry bulb only.
mefenoxam + copper hydroxide (Ridomil Gold Copper): 2 lb/A; PHI 10d, REI 48h, Groups 4 & M01.

FRAC Group M03:

mancozeb (Dithane M45): 3 qt/A; PHI 7d, REI 24h.
mancozeb + copper hydroxide (ManKocide): 2.5 lb/A; PHI 7d, REI 48h, Groups M03 & M01.
mefenoxam + mancozeb (Ridomil Gold MZ): 2.5 lb/A; PHI 7d, REI 48h, Groups 4 & M03. Do not apply to exposed bulbs.
zoxamide + mancozeb (Gavel 75 DF): 1.5 to 2 lb/A; PHI 7d, REI 48h, Groups 22 & M03. Do not apply to exposed bulbs.

FRAC Group M05:

azoxystrobin + chlorothalonil (Quadris Opti): 2.4 to 3.6 pt/A; PHI 7d, REI 12h, Groups 11 & M05. See label for tank mix precautions.
mefenoxam + chlorothalonil (Ridomil Gold Bravo SC): 2.5 pt/A; PHI 7d, REI 48h, Groups 4 & M05.
oxathiapiprolin + chlorothalonil (Orondis Opti): 1.75 to 5 pt/A; PHI 7d, REI 12h, Groups 49 & M05.
potassium phosphite + chlorothalonil (Catamaran): 4 to 7 pt/A; PHI 7d (dry bulb), REI 12h, Groups P07 & M05.
zoxamide + chlorothalonil (Zing!): 30.0 fl oz/A; PHI 7d, REI 12h, Groups 22 & M05. Do not apply to exposed bulbs.

FRAC Group P01:

acibenzolar-s-methyl (Actigard 50 WG): 0.75 to 1.0 oz/A; PHI 7d, REI 12h. Suppression only.

FRAC Group P07:

potassium phosphite + chlorothalonil (Catamaran): 4.0 to 7.0 pt/A; PHI 7d (dry bulb), REI 12h, Groups P07 & M05.

For green or bunching onions:

FRAC Group 4:

mefenoxam + chlorothalonil (Ridomil Gold Bravo SC): 2.5 pt/A; PHI 14d, REI 48h, Groups 4 & M05. Use preventively.
mefenoxam + copper hydroxide (Ridomil Gold Copper): 2 lb/A; PHI 7d, REI 48h, Groups 4 & M01.

FRAC Group 7:

fluxapyroxad + pyraclostrobin (Merivon Xemium): 8 to 11 fl oz/A; PHI 7d, REI 12, Groups 7 & 11. Use preventively. For suppression only.
pyraclostrobin + boscalid (Pristine): 18.5 oz/A; PHI 7d, REI 12h, Groups 7 & 11. Suppression only. Rotate with a downy mildew fungicide from a different FRAC Group.

FRAC Group 11:

azoxystrobin (Quadris F): 9 to 15.5 fl oz/A; PHI 0d, REI 4h.
azoxystrobin + chlorothalonil (Quadris Opti): 2.4 to 3.7 pt/A; PHI 14d, REI 12h, Groups 11 & M05. See label for tank mix precautions.
famoxadone + cymoxanil (Tanos): 8 oz/A; PHI 3d, 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.
fluxapyroxad + pyraclostrobin (Merivon Xemium): 8 to 11 fl oz/A; PHI 7d, REI 12, Groups 7 & 11. Use preventively. For suppression only.
pyraclostrobin (Cabrio EG): 12 oz/A; PHI 7d, REI 12h.
pyraclostrobin + boscalid (Pristine): 18.5 oz/A; PHI 7d, REI 12h, Groups 7 & 11. Suppression only. Rotate with a downy mildew fungicide from a different FRAC Group.

FRAC Group 19:

polyoxin D zinc salt (Oso 5% SC^OG): 6.5 to 13 fl oz/A; PHI 0d, REI 4h.

FRAC Group 21:

cyazofamid (Ranman 400 SC): 2.75 to 3 fl oz/A; PHI 0d, REI 12h.

FRAC Group 22:

zoxamide + chlorothalonil (Zing!): 30 fl oz/A; PHI 7d, REI 12h, Groups 22 & M05.
zoxamide + mancozeb (Gavel 75 DF): 1.5 to 2 lb/A; PHI 7d, REI 48h, Groups 22 & M03.

FRAC Group 27:

famoxadone + cymoxanil (Tanos): 8 oz/A; PHI 3d, 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 40:

ametoctradin + dimethomorph (Zampro): 14 fl oz/A; PHI 0d, REI 12h, Groups 45 & 40.
dimethomorph (Forum): 6 fl oz/A; PHI 0d, REI 12h.
mandipropamid (Revus): 5.5 to 8 fl oz/A; PHI 7d, REI 4h. A silicone-based adjuvant must be added at recommended rates.

FRAC Group 45:

ametoctradin + dimethomorph (Zampro): 14 fl oz/A; PHI 0d, REI 12h, Groups 45 & 40.

FRAC Group 49:

oxathiapiprolin + chlorothalonil (Orondis Opti): 1.75 to 4 pt/A; PHI 14d, REI 12h, Groups 49 & M05.
oxathiapiprolin (Orondis Opti A): 2 to 4.8 fl oz/A; PHI 7d, REI 4h.

FRAC Group M01:

copper hydroxide (Kocide 3000): 0.75 to 1.5 lb/A; PHI 0d, REI 48h. Can cause phytotoxicity to leaves. 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-O^OG).
mefenoxam + copper hydroxide (Ridomil Gold Copper): 2 lb/A; PHI 7d, REI 48h, Groups 4 & M01.

FRAC Group M03:

zoxamide + mancozeb (Gavel 75 DF): 1.5 to 2 lb/A; PHI 7d, REI 48h, Groups 22 & M03.

FRAC Group M05:

azoxystrobin + chlorothalonil (Quadris Opti): 2.4 to 3.7 pt/A; PHI 14d, REI 12h, Groups 11 & M05. See label for tank mix precautions.
mefenoxam + chlorothalonil (Ridomil Gold Bravo SC): 2.5 pt/A; PHI 14d, REI 48h, Groups 4 & M05. Use preventively.
oxathiapiprolin + chlorothalonil (Orondis Opti): 1.75 to 4 pt/A; PHI 14d, REI 12h, Groups 49 & M05.
potassium phosphite + chlorothalonil (Catamaran): 4 to 7 pt/A; PHI 14d, REI 12, Groups P07 & M05.
zoxamide + chlorothalonil (Zing!): 30 fl oz/A; PHI 7d, REI 12h, Groups 22 & M05.

FRAC Group P07:

potassium phosphite + chlorothalonil (Catamaran): 4 to 7 pt/A; PHI 14d, REI 12, Groups P07 & M05.

Purple Blotch (Alternaria porri)

Alternaria porri is most likely to become problematic when temperatures are warm (77°F–85°F) with high humidity. Small lesions will form on stems or leaves, eventually enlarging and becoming tan or purple. The pathogen overwinters in allium crop residue. Disease development is favored by warm, moist conditions. Purple blotch is easily confused with Stemphylium leaf blight, which tends to produce darker lesions. While laboratory diagnoses are needed for proper identification, these two pathogens can be managed in the same way. Practice long rotations with non-Allium crops, and use practices that reduce hours of leaf wetness, e.g., increased plant spacing and good air movement. Drip irrigation is preferable overhead. Remove or plow under crop residues promptly after harvest. Sweet Spanish onions are considered to be extremely susceptible. Apply fungicides as canopy becomes denser and leaf-wetness periods increase. Purple blotch disease development, based on weather conditions near your farm, can be monitored online at the Network for Environment and Weather Applications (NEWA).

FRAC Group 2:

iprodione (Rovral 4F): 1.5 pt/A (alone), 1 pt/A (tank-mix); PHI 7d, REI 24h. Dry bulb only.

FRAC Group 3:

azoxystrobin + difenoconazole (Quadris Top): 12 to 14 fl oz/A; PHI 7d, REI 12h, Groups 3 & 11.
azoxystrobin + propiconazole (Quilt Xcel): 14 to 21 fl oz/A; PHI 14d (dry bulb), 0d (green), REI 12h, Groups 11 & 3.
difenoconazole + benzovindiflupyr (Aprovia Top): 10.5 fl oz/A; PHI 7d, REI 12h, Groups 3 & 7.
difenoconazole + cyprodinil (Inspire Super): 14 to 20 fl oz/A; PHI 7d (dry bulb), 14d (green), REI 12h, Group 3 & 9.
propiconazole (PropiMax EC): 2 to 4 fl oz/A; PHI 14d (dry bulb), 0d (green), REI 12h.
tebuconazole (Orius 3.6F): 4 to 6 fl oz/A; PHI 7d, REI 12h. Dry bulb only.

FRAC Group 7:

boscalid (Endura): 6.8 oz/A; PHI 7d, REI 12h. Apply in-furrow.
difenoconazole + benzovindiflupyr (Aprovia Top): 10.5 fl oz/A; PHI 7d, REI 12h, Groups 3 & 7.
fluopyram + pyrimethanil (Luna Tranquility): 16 to 27 fl oz/A; PHI 7d, REI 12h, Groups 7 & 9. Do not make more than 2 sequential applications before alternating to a non-Group 7 or 9 fungicide.
fluxapyroxad + pyraclostrobin (Merivon Xemium): 5.5 to 11 fl oz/A; PHI 7d, REI 12, Groups 7 & 11. Use preventively.
penthiopyrad (Fontelis): 16 to 24 oz/A; PHI 3d, REI 12h.
pyraclostrobin + boscalid (Pristine): 10.5 to 18.5 oz/A; PHI 7d, REI 12h, Groups 7 & 11. Do not rotate with another Group 11 fungicides.

FRAC Group 9:

cyprodinil (Vangard WG): 10 oz/A; PHI 7d, REI 12h.
cyprodinil + fludioxonil (Switch 62.5 WDG): 11 to 14 oz/A; PHI 7d, REI 12h, Groups 9 & 12.
difenoconazole + cyprodinil (Inspire Super): 14 to 20 fl oz/A; PHI 7d (dry bulb), 14d (green), REI 12h, Group 3 & 9.
fluopyram + pyrimethanil (Luna Tranquility): 16 to 27 fl oz/A; PHI 7d, REI 12h, Groups 7 & 9. Do not make more than 2 applications before alternating to a non-Group 7 or 9 fungicide.
pyrimethanil (Scala SC): 18 fl oz/A (alone), 9 to 18 fl oz/A (tank-mix); PHI 7d, REI 12h.

FRAC Group 11:

azoxystrobin (Quadris F): 6 to 12 fl oz/A; PHI 0d, REI 4h. Do not rotate with other Group 11 fungicides.
azoxystrobin + chlorothalonil (Quadris Opti): 1.6 to 3.2 pt/A; PHI PHI 7d (dry bulb), 14d (green), REI 12h, Groups 11 & M05. See label for tank mix precautions.
azoxystrobin + difenoconazole (Quadris Top): 12 to 14 fl oz/A; PHI 7d, REI 12h, Groups 3 & 11.
azoxystrobin + propiconazole (Quilt Xcel): 14 to 21 fl oz/A; PHI 14d (dry bulb), 0d (green), REI 12h, Groups 11 & 3.
famoxadone + cymoxanil (Tanos): 8 oz/A; PHI 3d, 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 fl oz/A; PHI 7d, REI 12h. Do not make more than 1 application before alternating to a non-Group 11 fungicide.
famoxadone + cymoxanil (Tanos): 8 oz/A; PHI 3d, 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 fl oz/A; PHI 7d, REI 12h. Do not make more than 1 application before alternating to a non-Group 11 fungicide.
fluxapyroxad + pyraclostrobin (Merivon Xemium): 5.5 to 11 fl oz/A; PHI 7d, REI 12, Groups 7 & 11. Use preventively.
pyraclostrobin (Cabrio EG): 8 to 12 oz/A; PHI 7d, REI 12h. Do not rotate with other Group 11 fungicides.
pyraclostrobin + boscalid (Pristine): 10.5 to 18.5 oz/A; PHI 7d, REI 12h, Groups 7 & 11. Do not rotate with another Group 11 fungicides.

FRAC Group 12:

cyprodinil + fludioxonil (Switch 62.5 WDG): 11 to 14 oz/A; PHI 7d, REI 12h, Groups 9 & 12.

FRAC Group 19:

polyoxin D zinc salt (Oso 5%SC^OG): 6.5 to 13 fl oz/A; PHI 0d, REI 4h.

FRAC Group 27:

famoxadone + cymoxanil (Tanos): 8 oz/A; PHI 3d, 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 29:

fluazinam (Omega 500F): 16 fl oz/A; PHI 7d, REI 12h, 24h (hand weeding).

FRAC Group BM02:

Bacillus amyloliquefaciens strain D747 (Double Nickel 55^OG): 0.125 to 1 lb/A (soil), 0.25 to 3 lb/A (foliar); PHI 0d, REI 4h.

FRAC Group M01:

copper hydroxide (Kocide 3000): 0.75 to 1.5 lb/A; PHI 0d, REI 48h. Can cause phytotoxicity to leaves. 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-O^OG).
mancozeb + copper hydroxide (ManKocide): 2.5 lb/A; PHI 7d, REI 48h, Groups M03 & M01. Dry bulb onion only.

FRAC Group M03:

mancozeb (Dithane F45): 2.4 qt/A; PHI 7d, REI 24h. Dry bulb only.
mancozeb + copper hydroxide (ManKocide): 2.5 lb/A; PHI 7d, REI 48h, Groups M03 & M01. Dry bulb only.

FRAC Group M05:

azoxystrobin + chlorothalonil (Quadris Opti): 1.6 to 3.2 pt/A; PHI 7d (dry bulb), 14d (green), REI 12h, Groups 11 & M05. See label for tank mix precautions.
chlorothalonil (Bravo Weather Stik): 1 to 3 pt/A; PHI 7d (dry bulb), 14d (green), REI 12h.
potassium phosphite + chlorothalonil (Catamaran): 4 to 7 pt/A; PHI 7d (dry bulb), 14d (green), REI 12, Groups P07 & M05.

FRAC Group P07:

potassium phosphite + chlorothalonil (Catamaran): 4 to 7 pt/A; PHI 7d (dry bulb), 14d (green), REI 12, Groups P07 & M05.

Stemphylium leaf blight (Stemphylium spp.)

Stemphylium vesicarium and S. botryosum have been reported on onion in North America, while only S. botryosum has been reported on garlic. Symptoms begin as small, white, round to oval spots that enlarge to produce brown lesions. The lesions darken as the fungus sporulates, and brown to black concentric rings may be visible; in addition, lesions may have yellow margins, in contrast to the purple margins seen in purple blotch. Leaves may wilt and turn brown. A decrease in photosynthetic leaf area results in undersized bulbs, inferior quality, and reduced storage life. This pathogen has a broad host range including garlic, leek, onion, shallot, asparagus, tomato, radish, sunflower, parsley, alfalfa, and soybean. The fungus forms small black sclerotia that can persist in the soil for several years: it may also overwinter on crop residues and perennial weeds. Disease development is favored by warm, moist conditions. The recent emergence of Stemphylium has been associated with the development of resistance to single-site mode-of-action fungicides, including strobilurins (Group 11). Crop rotation for at least one year may reduce inoculum density. Additionally, post-harvest residue removal is an important means to decrease overwintering inoculum between seasons. Purchase less susceptible varieties when available and plant in well-drained soil. Avoid excessive nitrogen fertilization as this increases disease susceptibility. Select sites and implement cultural practices to enhance air circulation and rapid drying of foliage. Weed control and disease-free seed cloves for field establishment are essential.

FRAC Group 2:

iprodione (Rovral 4F): 1.5 pt/A (alone), 1 pt/A (tank-mix); PHI 7d, REI 24h. Dry bulb only.

FRAC Group 3:

difenoconazole + benzovindiflupyr (Aprovia Top): 10.5 fl oz/A; PHI 7d, REI 12h, Groups 3 & 7.
difenoconazole + cyprodinil (Inspire Super): 14 to 20 fl oz/A; PHI 7d (dry bulb), 14d (green), REI 12h, Groups 3 & 9.

FRAC Group 7:

difenoconazole + benzovindiflupyr (Aprovia Top): 10.5 fl oz/A; PHI 7d, REI 12h, Groups 3 & 7.
fluopyram + pyrimethanil (Luna Tranquility): 16 to 27 fl oz/A; PHI 7d, REI 12h, Groups 7 & 9. Do not make more than 2 sequential applications.
fluxapyroxad + pyraclostrobin (Merivon Xemium): 5.5 to 11 fl oz/A; PHI 7d, REI 12, Groups 7 & 11. Use preventively.
pyraclostrobin + boscalid (Pristine): 10.5 to 18.5 oz/A; PHI 7d, REI 12h, Groups 7 & 11. Do not rotate with another Group 11 fungicide.

FRAC Group 9:

cyprodinil + fludioxonil (Switch 62.5 WDG): 11 to 14 oz/A; PHI 7d, REI 12h, Groups 9 & 12.
difenoconazole + cyprodinil (Inspire Super): 14 to 20 fl oz/A; PHI 7d (dry bulb), 14d (green), REI 12h, Groups 3 & 9.
fluopyram + pyrimethanil (Luna Tranquility): 16 to 27 fl oz/A; PHI 7d, REI 12h, Groups 7 & 9. Do not make more than 2 sequential applications.

FRAC Group 11:

fluxapyroxad + pyraclostrobin (Merivon Xemium): 5.5 to 11 fl oz/A; PHI 7d, REI 12, Groups 7 & 11. Use preventively.
pyraclostrobin (Cabrio EG): 8 to 12 oz/A; PHI 7d, REI 12h. Do not rotate with other Group 11 fungicides.
pyraclostrobin + boscalid (Pristine): 10.5 to 18.5 oz/A; PHI 7d, REI 12h, Groups 7 & 11. Do not rotate with another Group 11 fungicide.

FRAC Group 12:

cyprodinil + fludioxonil (Switch 62.5 WDG): 11 to 14 oz/A; PHI 7d, REI 12h, Groups 9 & 12.

White Rot (Sclerotium cepivorum)

White rot is caused by Sclerotium cepivorum, which persists for a long time in soil. It is “activated” by root exudates produced by allium crops. Affected plants will show yellowing older leaves and stunting. White, cottony mycelium appears on infected tissues, but it is rapidly converted to masses of sclerotia. The sclerotia are round, black, and very small (0.35–0.75 mm). Symptoms may be widespread in the field, or they may occur in small patches which gradually expand. Disease development is favored by cool, moist soil conditions. Purchase disease-free seed and transplants. Avoid planting in fields with a history of white rot; there is little to be done once a field is infested with S. cepviorum, and crops should be rotated out of alliums for as long as possible. In general, neither fungicides nor soil fumigation have provided consistent, reliable, full-season control of white rot. Winter flooding and soil solarization can reduce the number of sclerotia.

FRAC Group 1:

thiophanate methyl (Topsin 4.5 FL): 40 fl oz/A; REI 72h. Apply in furrow. Do not apply more than once per year.

FRAC Group 3:

azoxystrobin + propiconazole (Quilt Xcel): 17.5 to 21 fl oz/A; PHI 14d (dry bulb), 0d (green), REI 12h, Group 3 & 11.
tebuconazole (Orius 3.6F): 20.5 fl oz/A; PHI 7d, REI 12h. Apply in-furrow or chemigation. Dry bulb only.

FRAC Group 7:

boscalid (Endura): 6.8 oz/A; PHI 7d, REI 12h. Apply in-furrow.
penthiopyrad (Fontelis): 16 to 24 oz/A; PHI 3d, REI 12h. Apply in-furrow.

FRAC Group 9:

cyprodinil + fludioxonil (Switch 6.25 WG): 7 to 14 oz/A; PHI 7d, REI 12h, Groups 9 & 12. Apply at planting as in-furrow spray.

FRAC Group 11:

azoxystrobin + propiconazole (Quilt Xcel): 17.5 to 21 fl oz/A; PHI 12d (dry bulb), 0d (green), REI 12h, Group 3 & 11

FRAC Group 12:

cyprodinil + fludioxonil (Switch 6.25 WG): 7 to 14 oz/A; PHI 7d, REI 12h, Groups 9 & 12. Apply at planting as in-furrow spray.
fludioxonil (Cannonball WG): 7 oz/A (0.5 oz/1,000 ft row); PHI 7d, REI 12h.