Onion, Scallion, and Shallot

Onion, Scallion, and Shallot ashahane Tue, 05/21/2024 - 15:50

Onion, Scallion & Shallot Disease Control Onion, Scallion & Shallot Insect Control Onion, Scallion & Shallot Weed Control

Introduction

Bulbing onion, scallion, and shallot, along with garlic and leek, are members of the genus Allium. The characteristic flavors of Allium family members come from sulfur-containing compounds produced by these plants.

The bulbing onion, Allium cepa, appears to have originated near the intersection of Europe and Asia, whereas the bunching onion or scallion, A. fistulosum may have originated in China.

Types and Varieties

Bulbing onions form bulbs in response to day length. Only long-day and intermediate-day types are recommended for summer harvest in New England since these types require at least 13 hours of daylight. Short-day onions begin forming bulbs when days are 10-12 hours long and are typically grown in southern regions of the U.S. where they are planted in the winter. Recently, some researchers and farmers in New England have been planting onions in low tunnels in the fall for spring harvest. The University of New Hampshire research report on overwintering onions includes planting details and trialed varieties (see https://bit.ly/overwinteronions). Shallots form clusters of bulbs. While shallots have traditionally been propagated vegetatively, hybrid cultivars that can be grown from seed are now available. Scallions do not form a fully developed bulb. They are planted from seed and commonly sold in bunches.

Type	Varieties
Scallion/Bunching Onion	Deep Purple (Red) Evergreen Hardy White Nebachen
Shallot	Ambition Conservor
Onion - Sets	Ebenezer Stuttgart
Onion - Sweet, non-storing	Alisa Craig (110) Candy (85)
Onion - Sweet Spanish	Super Star (100) Yellow Sweet Spanish (120)
Onion - Yellow Storage	Bridger (90) New York Early (98) Patterson (104) Cortland (105) Powell (108) Crocket (114)
Onion - Red Storage	Red Bull (104) Red Carpet (114) Redwing (114)
Onion - Overwintering	Bridger Hi-Keeper Red Rock (red) Red Spring (red) T-448

The number in parentheses is the approximate number of days to maturity from seeding.

Soil Fertility

Apply lime according to soil test results to maintain soil pH at 6.5-6.8. Onions do not tolerate acid soil, especially in early growth stages. If the magnesium level is high, a lime high in calcium (calcitic lime) should be used to maintain a high calcium level.

Less nitrogen fertilizer will be needed if legume sod was plowed down or if manure was applied (see Table 1 and Table 7). These sources may also result in high soil nitrogen levels late in the season. Excessive nitrogen late in the season from any source can delay maturity and reduce storability of onions.

Onion flavor is determined by cultivar type, temperature and irrigation, and sulfur fertility. Growers wishing to produce mild-flavored onions for retail sale should choose mild cultivar types, irrigate regularly up to harvest, and maintain soil sulfur levels between 35 and 55 lb/A. Excessive sulfur levels in soils or fertilizers will increase pungency.

Plant Nutrient Recommendations According to Soil Test Results for Onion, Scallion, and Shallot

SOIL TEST RESULTS	NITROGEN (N) - LBS PER ACRE	PHOSPHORUS (P) - LBS P₂O₅ PER ACRE				POTASSIUM (K) - LBS K₂O PER ACRE
SOIL TEST RESULTS	NITROGEN (N) - LBS PER ACRE	VERY LOW	LOW	OPTIMUM	ABOVE OPTIMUM	VERY LOW	LOW	OPTIMUM	ABOVE OPTIMUM
Broadcast and incorporate	80-100	150	100	25-50	0	175	150	50	0
Sidedress 4-5 weeks after planting	50	0	0	0	0	0	0	0	0
TOTAL RECOMMENDED	130-150	150	100	25-50	0	175	150	50	0

Planting

Bulbing onion and shallot. Sow transplants in late February or early March, 10-12 weeks before setting in field. Direct-seed onions in spring as soon as soil can be worked. Seeding should be completed by late April or mid-May at the very latest to allow time for adequate plant growth before bulb initiation occurs. Plant 2-4 rows per bed, 9-18" between rows and 3-4" apart within rows for transplants. Spacing will affect bulb size. For direct seeding, aim for a stand of 6-9 plants per foot. This can be increased to 9-12 plants per foot if double shoe precision seeders are used. This requires 5-6 lb of seed per acre (about 0.5 oz per 100 feet of row). Instead of transplants, some growers use sets to plant all or some of their crop. Sets are small bulbs (about 1/2") raised the prior year and stored over the winter. This provides for an early harvest (mid-summer), but larger sets can be prone to bolting (premature flowering). Sets should be planted as soon as the soil has dried and can be worked. Spacing is the same as for transplants. Some growers are finding success using black or white-on-black plastic mulch on raised beds for sets or transplants.

Scallion. In addition to early spring planting, mid-summer plantings can be used to produce fall harvests. Even moisture must be maintained throughout germination for direct-sown scallions. Seed in rows 2-3” wide, spaced 4” apart.

Harvest and Storage

Bulbing onion and shallot. Late, hard, pungent varieties with good skin retention are preferable for winter storage. Undercutting several days before harvesting can improve keeping quality. It is best to undercut when most of the plants have 2 leaves that are still partially green. Allowing leaves to completely dry down before undercutting can result in excessive loss of skin during harvest. To develop best skin color, onions should be cured for 2 weeks at 75-80ºF and 70-80% relative humidity. After curing, lower temperature gradually to as near to 32ºF as practical without freezing. Cooling too rapidly, followed by a few warm days, can cause moisture condensation, resulting in bulb staining, sprouting, and decay. Maintain storage relative humidity at 65-70%, and maintain sufficient air flow to keep cool air moving around bulbs.

Scallion. Scallions, or fresh bunching onions, can be harvested anytime after they are pencil-sized. To maintain good post-harvest quality, they should be cooled to 39ºF within 4-6 hours of harvest. Scallions can be stored for 7-10 days at 32ºF.

Sprout Inhibition

For long-term storage of bulbing onions or shallots, select storage varieties. Pungent dry onions can be stored for 6-9 months at 32ºF. For very long-term storage, a sprouting inhibitor, maleic hydrazide (2 gal of Royal MH-30/A in a minimum of 30 gal/A), may be applied when about 50% of the tops are down, the bulbs are mature, the necks are soft and 5-7 of the leaves are still green. See the label for details.

Onion, Scallion, and Shallot Disease Control

Onion, Scallion, and Shallot Disease Control ashahane Wed, 05/29/2024 - 09:20

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

NOTE: For the disease control products listed below, one product trade name and formulation is provided for each active ingredient (common name) as an example of rates, preharvest interval (PHI), restricted entry interval (REI), and special instructions. In many cases, there are other products available with the same active ingredient. Please see Table 25 and Fungicides and Bactericides Alphabetically Listed by Trade Name for more information on products with the same active ingredients.

The symbol ^OG indicates a product is listed by the Organic Materials Review Institute (OMRI) as approved for use in organic production. See Organic Certification section for more detail.

Botrytis Leaf Blight (Botrytis squamosa)

Avoid close planting and orient rows in the direction of prevailing winds. Do not plant on poorly-drained areas. 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 (www.newa.cornell.edu).

For dry bulb onions:

azoxystrobin (Quadris F): 9.0 to 15.5 fl oz/A; PHI 0d, REI 4h, Group 11.
azoxystrobin plus chlorothalonil (Quadris Opti): 1.6 to 3.2 pt/A; PHI 7d, REI 12h, Groups 11 & M05.
azoxystrobin plus difenoconazole (Quadris Top): 8.0 to 14.0 fl oz/A; PHI 7d, REI 12h, Groups 11 & 3.
azoxystrobin plus propiconazole (Quilt): 14.0 to 27.5 fl oz/A; PHI 14d, REI 12h, Groups 11 & 3.
boscalid (Endura): 6.8 oz/A; PHI 7d, REI 12h, Group 7.
chlorothalonil (Bravo Weather Stik): 1.0 to 3.0 pt/A; PHI 7d, REI 12h, Group M05. 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.
cyprodinil (Vanguard): 5.5 to 10.0 oz/A; PHI 7d, REI 12h, Group 9.
cyprodinil plus fludioxonil (Switch 62.5 WG): 11.0 to 14.0 oz/A; PHI 7d, REI 12h, Groups 9 & 12.
difenoconazole plus cyprodinil (Inspire Super): 14.0 to 20.0 fl oz/A; PHI 7d, REI 12h, Group 3 & 9. Apply in sufficient volume to achieve thorough coverage.
fluazinam (Omega 500F): 16.0 fl oz/A; PHI 7d, REI 12h to 24h (24h for hand weeding), Group 29.
fluopyram plus 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 plus pyraclostrobin (Merivon Xemium): 8.0 to 11.0 fl oz/A; PHI 7d, REI 12, Groups 7 & 11. For best results, begin applications before disease onset.
iprodione (Rovral 4F): 1.5 pt/A (alone) or 1.0 pt/A (if tank-mixed); PHI 7d, REI 24h, Group 2. See label for application methods and restrictions.
mancozeb (Dithane F45): 2.4 qt/A; PHI 7d, REI 24h, Group M03.
penthiopyrad (Fontelis): 16 to 24 oz/A; PHI 3d, REI 12h, Group 7.
polyoxin D zinc salt (VEGGIETURBO 5%SC^OG): 6.5 to 13.0 fl oz/A; PHI 0d, REI 4h, Group 19.
potassium phosphite plus chlorothalonil (Catamaran): 4.0 to 7.0 pt/A; PHI 7d, REI 12, Groups P07 & M05.
propiconazole (Tilt): 4.0 to 8.0 oz/A; PHI 14d, REI 12, Group 3.
pyraclostrobin (Cabrio EG): 12.0 oz/A; PHI 7d, REI 12h, Group 11. For suppression only. Do not exceed 6 applications per season or 72 oz/A. Do not rotate with other Group 11 fungicides.
pyraclostrobin plus boscalid (Pristine): 14.5 to 18.5 oz/A; PHI 7d, REI 12h, Groups 11 & 7. Do not make more than 2 sequential applications before alternating with a fungicide from a different FRAC Group.
pyrimethanil (Scala SC): 18.0 fl oz/A; PHI 7d, REI 12h, Group 9.

For green onions and shallots:

azoxystrobin (Quadris F): 9.0 to 15.5 fl oz/A; PHI 0d, REI 4h, Group 11.
azoxystrobin plus chlorothalonil (Quadris Opti): 1.6 to 3.2 pt/A; PHI 14d, REI 12h, Groups 11 & M05. See label for tank mix precautions.
azoxystrobin plus difenoconazole (Quadris Top): 8.0 to 14.0 fl oz/A; PHI 1d, REI 12h, Groups 11 & 3.
azoxystrobin plus propiconazole (Quilt): 14.0 to 27.5 fl oz/A; PHI 0d, REI 12h, Groups 11 & 3.
boscalid (Endura): 6.8 oz/A; PHI 7d, REI 12h, Group 7. Use higher rate and shorter interval when disease pressure is high. Do not make more than 1 application of Endura before alternating with a fungicide from a different FRAC Group.
chlorothalonil (Bravo Weather Stik): 1.5 to 3.0 pt/A; PHI 14d, REI 12h, Group M05. When disease is present, use the higher rate.
cyprodinil (Vanguard): 5.5 oz/A; PHI 7d, REI 12h, Group 9.
cyprodinil plus fludioxonil (Switch 62.5 WDG): 11.0 to 14.0 oz/A; PHI 7d, REI 12h, Groups 9 & 12.
difenoconazole plus cyprodinil (Inspire Super): 14.0 to 20.0 fl oz/A; PHI 14d, REI 12h, Group 3 & 9.
fluopyram plus pyrimethanil (Luna Tranquility): 16.0 to 27.0 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 plus pyraclostrobin (Merivon Xemium): 8.0 to 11.0 fl oz/A; PHI 7d, REI 12, Groups 7 & 11. For best results, begin applications before disease onset.
penthiopyrad (Fontelis): 16.0 to 24.0 oz/A; PHI 3d, REI 12h, Group NC.
polyoxin D zinc salt (VEGGIETURBO 5%SC^OG): 3.75 to 13.0 fl oz/A; PHI 0d, REI 4h, Group 19.
potassium phosphite plus chlorothalonil (Catamaran): 4.0 to 7.0 pt/A; PHI 14d, REI 12, Groups P07 & M05.
propiconazole (Tilt): 4.0 to 8.0 oz/A; PHI 0d, REI 12, Group 3.
pyraclostrobin plus boscalid (Pristine): 14.5 to 18.5 oz/A; PHI 7d, REI 12h, Groups 11 & 7. Do not make more than 2 sequential applications before alternating with a fungicide from a different FRAC Group.
pyrimethanil (Scala SC): 18.0 fl oz/A; PHI 7d, REI 12h, Group 9.

Botrytis Neck Rot (Botrytis alli)

Primarily a storage disease. 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 32-33°F and 70-75% relative humidity. Fungicides applied to control Botrytis leaf blight may also decrease neck rot.

azoxystrobin plus 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.
cyprodinil plus fludioxonil (Switch 6.25 WG): 11.0 to 14.0 oz/A; PHI 7d, REI 12h, Groups 9 & 12. Suppression only.
fluazinam (Omega 500F): 16.0 fl oz/A; PHI 7d, REI 48h, 24h if hand weeding, Group 29. REI 24h for hand weeding
fluxapyroxad plus pyraclostrobin (Merivon Xemium): 8.0 to 11.0 fl oz/A; PHI 7d, REI 12, Groups 7 & 11. For best results, begin applications before disease onset.
iprodione (Rovral 4F): 1.5 pt/A (alone) or 1.0 pt/A (if tank-mixed); PHI 7d, REI 24h, Group 2. Dry bulb onion only. See label for application and restrictions.
mancozeb (Dithane M45): 2.4 qt/A; PHI 7d, REI 24h, Group M03.
polyoxin D zinc salt (VEGGIETURBO 5%SC^OG): 3.75 to 13.0 fl oz/A; PHI 0d, REI 4h, Group 19.
pyraclostrobin plus boscalid (Pristine): 14.5 to 18.5 oz/A; PHI 7d, REI 12h, Groups 11 & 7.
pyrimethanil (Scala SC): 18.0 fl oz/A; PHI 7d, REI 12h, Group 9.

Downy Mildew (Peronospora destructor)

Downy mildew of allium crops is caused by a fungal-like pathogen that overwinters in infected bulbs or sets and on other host plants, in cull piles, and in fall-seeded onion. Only a few spores are needed to initiate an epidemic. Eliminate cull piles, volunteer onion plants, and wild Allium species. Practice a 3- to 4-year rotation. Plant only on well-drained land. 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 (www.newa.cornell.edu).

For dry bulb onions:

acibenzolar-s-methyl (Actigard 50 WG): 0.75 to 1.0 oz/A; PHI 7d, REI 12h, Group P01. Actigard acts as a plant activator and should be applied preventatively.
ametoctradin plus dimethomorph (Zampro): 14.0 fl oz/A; PHI 0d, REI 12h, Groups 45 & 40. See label for application restriction.
azoxystrobin (Quadris F): 9.0 to 15.5 fl oz/A; PHI 0d, REI 4h, Group 11.
azoxystrobin plus chlorothalonil (Quadris Opti): 2.4 to 3.6 pt/A; PHI 7d, REI 12h, Groups 11 & M05. See label for tank mix precautions.
copper hydroxide (Kocide 3000): 0.75 to 1.5 lb/A; PHI 0d, REI 48h, Group M01. Can cause phytotoxicity to leaves. Do not apply in a spray solution having a pH less than 6.5 or tank mix with Aliette.
cyazofamid (Ranman 400 SC): 2.75 to 3.0 fl oz/A; PHI 0d, REI 12h, Group 21.
dimethomorph (Forum): 6.0 fl oz/A; PHI 0d, REI 12h, Group 40. Forum can be applied as a tank mix with another fungicide from a different FRAC Group. Minimum application interval is 5 days.
famoxadone plus cymoxanil (Tanos): 8.0 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, Group 11. Do not make more than 1 application before alternating to a non-Group 11 fungicide. Max application of 22 fl oz/ acre per year. Not for sale, distribution, or use in Nassau or Suffolk County, New York.
fluazinam (Omega 500F): 16.0 fl oz/A; PHI 7d, REI 48h, 24h if hand weeding, Group 29.
fluxapyroxad plus pyraclostrobin (Merivon Xemium): 8.0 to 11.0 fl oz/A; PHI 7d, REI 12, Groups 7 & 11. For best results, begin applications before disease onset. For supression only.
mancozeb (Dithane M45): 2.4 qt/A; PHI 7d, REI 24h, Group M03.
mancozeb plus copper hydroxide (ManKocide): 2.5 lb/A; PHI 7d, REI 48h, Groups M03 & M01.
mandipropamid (Revus): 5.5 to 8.0 fl oz/A; PHI 7d, REI 4h, Group 40. A silicone-based adjuvant must be added at recommended rates. Max application limit varies for dry bulb and green onions. See label for details.
mefenoxam plus chlorothalonil (Ridomil Gold Bravo SC): 2.5 pt/A; PHI 7d, REI 48h, Groups 4 & M05.
mefenoxam plus copper hydroxide (Ridomil Gold Copper): 2.0 lb/A; PHI 10d, REI 48h, Groups 4 & M01.
mefenoxam plus mancozeb (Ridomil Gold MZ): 2.5 lb/A; PHI 7d, REI 48h, Groups 4 & M03.
oxathiapiprolin plus chlorothalonil (Orondis Opti): 1.75 to 2.5 pt/A; PHI 7d, REI 12h, Groups 49 & M05.
oxathiapiprolin (Orondis Ultra A): 2.0 to 4.8 fl oz/A; PHI 0d, REI 4h, Groups U15. Do not exceed more than 6 applications per acre per year.
polyoxin D zinc salt (VEGGIETURBO 5%SC^OG): 6.5 to 13.0 fl oz/A; PHI 0d, REI 4h, Group 19.
potassium phosphite plus chlorothalonil (Catamaran): 4.0 to 7.0 pt/A; PHI 7d, REI 12, Groups P07 & M05.
pyraclostrobin (Cabrio EG): 12.0 oz/A; PHI 7d, REI 12h, Group 11. Do not exceed 6 applications per season or 72 oz/A. Do not rotate with other Group 11 fungicides.
pyraclostrobin plus 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): 1.0 to 3.0 qt/100 gal; PHI 0d, REI 4h, Group P07. Do not apply to heat- or moisture-stressed plants or to plants recently treated with copper.
zoxamide plus chlorothalonil (Zing!): 30.0 fl oz/A; PHI 7d, REI 12h, Groups 22 & M05. Do not make more than 8 applications or apply more than 1.33 lb zoxamide and 7.84 lb chlorothalonil per acre per year.
zoxamide plus mancozeb (Gavel 75 DF): 1.5 to 2 lb/A; PHI 7d, REI 48h, Groups 22 & M03. Do not make more than 8 applications or apply more than 16 lbs. (10.67 lb mancozeb and 1.33 zoxamide) per acre per year.

Green or bunching onions:

ametoctradin plus dimethomorph (Zampro): 14.0 fl oz/A; PHI 0d, REI 12h, Groups 45 & 40. See label for application restrictions.
azoxystrobin (Quadris F): 9.0 to 15.5 fl oz/A; PHI 0d, REI 4h, Group 11.
azoxystrobin plus chlorothalonil (Quadris Opti): 2.4 to 3.7 pt/A; PHI 14d, REI 12h, Groups 11 & M05. See label for tank mix precautions.
copper hydroxide (Kocide 3000): 0.75 to 1.5 lb/A; PHI 0d, REI 48h, Group M01. Can cause phytotoxicity to leaves. Do not apply in a spray solution having a pH less than 6.5 or tank mix with Aliette.
cyazofamid (Ranman 400 SC): 2.75 to 3.0 fl oz/A; PHI 0d, REI 12h, Group 21.
dimethomorph (Forum): 6.0 fl oz/A; PHI 0d, REI 12h, Group 40. Forum can be applied as a tank mix with another fungicide with a different mode of action. Minimun application interval is 5 days.
famoxadone plus cymoxanil (Tanos): 8.0 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 plus pyraclostrobin (Merivon Xemium): 8.0 to 11.0 fl oz/A; PHI 7d, REI 12, Groups 7 & 11. For best results, begin applications before disease onset. For supression only.
mandipropamid (Revus): 5.5 to 8.0 fl oz/A; PHI 7d, REI 4h, Group 40. A silicone-based adjuvant must be added at recommended rates. Max application limit varies for dry bulb and green onions. See label for details.
mefenoxam plus chlorothalonil (Ridomil Gold Bravo SC): 2.5 pt/A; PHI 14d, REI 48h, Groups 4 & M05.
mefenoxam plus copper hydroxide (Ridomil Gold Copper): 2.0 lb/A; PHI 7d, REI 48h, Groups M4 & M01.
oxathiapiprolin plus chlorothalonil (Orondis Opti): 1.75 to 2.5 pt/A; PHI 14d, REI 12h, Groups 49 & M05.
oxathiapiprolin (Orondis Ultra A): 2.0 to 4.8 fl oz/A; PHI 7d, REI 4h, Groups 49 & 40. Do not exceed more than 6 applications per acre per year.
polyoxin D zinc salt (VEGGIETURBO 5%SC^OG): 6.5 to 13.0 fl oz/A; PHI 0d, REI 4h, Group 19.
potassium phosphite plus chlorothalonil (Catamaran): 4.0 to 7.0 pt/A; PHI 14d, REI 12, Groups P07 & M05.
pyraclostrobin (Cabrio EG): 12.0 oz/A; PHI 7d, REI 12h, Group 11. Do not exceed 6 applications per season or 72 oz/A. Do not rotate with other Group 11 fungicides.
pyraclostrobin plus 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.
zoxamide plus chlorothalonil (Zing!): 30.0 fl oz/A; PHI 7d, REI 12h, Groups 22 & M05. Do not make more than 8 applications or apply more than 1.33 lb zoxamide and 7.84 lb chlorothalonil per acre per year.
zoxamide plus mancozeb (Gavel 75 DF): 1.5 to 2 lb/A; PHI 7d, REI 48h, Groups 22 & M03. Do not make more than 8 applications or apply more than 16 lbs. (10.67 lb mancozeb and 1.33 zoxamide) per acre per year.

Purple Blotch (Alternaria porri)

The pathogen overwinters in allium crop residue. Disease development is favored by warm, moist conditions. Avoid Sweet Spanish onions because they are extremely susceptible. Plow under crop residues after harvest. Rotate with non-allium crops. Select sites and practice irrigation to enhance rapid drying of foliage. 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 (www.newa.cornell.edu).

azoxystrobin (Quadris F): 6.0 to 12.0 fl oz/A; PHI 0d, REI 4h, Group 11. Do not rotate with other Group 11 fungicides.
azoxystrobin plus chlorothalonil (Quadris Opti): 1.6 to 3.2 pt/A; PHI 7d (dry), 14d (green), REI 12h, Groups 11 & M05. See label for tank mix precautions.
azoxystrobin plus difenoconazole (Quadris Top): 8.0 to 14.0 fl oz/A; PHI 7d, REI 12h, Groups 3 & 11.
azoxystrobin plus propiconazole (Quilt): 14.0 to 27.5 fl oz/A; PHI 14d (dry), 0d (green), REI 12h, Groups 11, 7 & 3.
Bacillus amyloliquefaciens strain D747 (DoubleNickel LC) OG: 0.25 to 3.0 lb/A; PHI 0d, REI 4h, Group BM02. Suppression only. For improved control, mix or rotate with a chemical fungicide.
boscalid (Endura): 6.8 oz/A; PHI 7d, REI 12h, Group 7.
chlorothalonil (Bravo Weather Stik): 1.0 to 3.0 pt/A; PHI 7d (dry), 14d (green), REI 12h, Group M05.
copper hydroxide (Kocide 3000): 0.75-1.5 lb/A; PHI 0d, REI 48h, Group M01. Do not apply in a spray solution having a pH less than 6.5 or tank mix with Aliette.
cyprodinil (Vanguard): 10.0 oz/A; PHI 7d, REI 12h, Group 9.
cyprodinil plus fludioxonil (Switch 62.5 WDG): 11.0 to 14.0 oz/A; PHI 7d, REI 12h, Groups 9 & 12.
difenoconazole plus benzovindiflupyr (Aprovia Top): 10.5 fl oz/A; PHI 7d, REI 12h, Groups 3 & 7. No more than 2 sequential applications before alternating to a non-Group 7 fungicide.
difenoconazole plus cyprodinil (Inspire Super): 14.0 to 20.0 fl oz/A; PHI 7d (dry bulb), 14d (green), REI 12h, Group 3 & 9. Apply in sufficient volume to achieve thorough coverage.
famoxadone plus cymoxanil (Tanos): 8.0 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, Group 11. Do not rotate with other Group 11 fungicides. Do not make more than 1 application before alternating to a non-Group 11 fungicide. Max application of 22 fl oz/acre per year. Not for sale, distribution or use in Nassau or Suffolk County, New York.
fluazinam (Omega 500F): 16 fl oz/A; PHI 7d, REI 12h, 24h for hand weeding, Group 29. Dry bulb only.
fluopyram plus pyrimethanil (Luna Tranquility): 16.0 to 27.0 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 plus pyraclostrobin (Merivon): 4.0 to 11 fl oz/A; PHI 7d, REI 12, Groups 7 & 11. For best results, begin applications before disease onset.
iprodione (Rovral 4F): 1.5 pt/A (alone) or 1.0 pt/A (if tank-mixed); PHI 7d, REI 24h, Group 2. Dry bulb only. Do not make more than 5 applications per season.
mancozeb (Dithane F45): 2.4 qt/A; PHI 7d, REI 24h, Group M03. Dry bulb onion only.
mancozeb plus copper hydroxide (ManKocide): 2.5 lb/A; PHI 7d, REI 48h, Groups M03 & M01. Dry bulb onion only.
penthiopyrad (Fontelis): 16.0 to 24.0 oz/A; PHI 3d, REI 12h, Group 7.
polyoxin D zinc salt (VEGGIETURBO 5%SC^OG): 6.5 to 13.0 fl oz/A; PHI 0d, REI 4h, Group 19.
potassium phosphite plus chlorothalonil (Catamaran): 4.0 to 7.0 pt/A; PHI 14d, REI 12, Groups P07 & M05.
propiconazole (PropiMax EC): 4.0 to 8.0 fl oz/A; PHI 14d bulb, PHI 0d green, REI 12h, Group 3.
pyraclostrobin (Cabrio EG): 8.0 to 12.0 oz/A; PHI 7d, REI 12h, Group 11. Do not exceed 6 applications per season or 72 oz/A. Do not rotate with other Group 11 fungicides.
pyraclostrobin plus boscalid (Pristine): 10.5 to 18.5 oz/A; PHI 7d, REI 12h, Groups 7 & 11. Do not rotate with another Group 11 fungicides.
pyrimethanil (Scala SC): 18.0 fl oz/A (alone), 9.0 fl oz/A (tank-mixed); PHI 7d, REI 12h, Group 9.
tebuconazole (Orius 3.6F): 4.0 to 6.0 fl oz/A; PHI 7d, REI 12h, Group 3. Dry bulb onion only.

Stemphylium leaf blight (Stemphylium vesicarium)

Symptoms appear as target-like brown lesions, lacking the purple margins seen with purple blotch. The pathogen overwinters on allium crop residues. Disease development is favored by warm, moist conditions. Plow under crop residues after harvest. Rotate with non-allium crops. Select sites and practice irrigation to enhance rapid drying of foliage. Apply fungicides as canopy becomes denser and leaf wetness periods increase.

difenoconazole plus benzovindiflupyr (Aprovia Top): 10.5 fl oz/A; PHI 7d, REI 12h, Groups 3 & 7. No more than 2 sequential applications before alternating to a non-Group 7 fungicide.
difenoconazole plus cyprodinil (Inspire Super): 14.0 to 20.0 fl oz/A; PHI 7d (dry bulb); PHI 14d (green), REI 12h, Group 3 & 9. Apply in sufficient volume to achieve thorough coverage.
fluopyram plus 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 plus pyraclostrobin (Merivon): 4 to 11 fl oz/A; PHI 7d, REI 12, Groups 7 & 11. For best results, begin applications before disease onset.
iprodione (Rovral 4F): 1.5 pt/A (alone) or 1.0 pt/A (if tank-mixed); PHI 7d, REI 24h, Group 2. Dry bulb only. Do not make more than 5 applications per season.
pyraclostrobin (Cabrio EG): 8.0 to 12.0 oz/A; PHI 7d, REI 12h, Group 11. Do not exceed 6 applications per season or 72 oz/A. Do not rotate with other Group 11 fungicides.
pyraclostrobin plus boscalid (Pristine): 10.5 to 18.5 oz/A; PHI 7d, REI 12h, Groups 7 & 11. Do not rotate with another Group 11 fungicide.

White Rot (Sclerotium cepivorum)

White rot is associated with soil-borne inoculum; repeated cropping of Allium species results in increased disease over time. The sclerotia can persist in the soil for up to 20 years in the absence of a host. Select fields with no history of this disease. Use only disease-free transplants. Soil fumigation may be useful. Stimulating the sclerotia to germinate with onion exudate mimics (diallyl disulphide) can reduce soil inoculum.

azoxystrobin plus propiconazole (Quilt Xcel): 17.5 to 21 fl oz/A; PHI 14d, REI 12h, Group 3 & 11.
Bacillus amyloliquefaciens strain D747 (DoubleNickel LC^OG): 0.12 to 1.0 lb/A as a soil drench; PHI 0d, REI 4 h, Group BM02.
boscalid (Endura): 6.8 oz/A; PHI 7d, REI 12h, Group 7. Apply in-furrow.
cyprodinil plus fludioxonil (Switch 6.25 WG): 7.0 to 14.0 oz/A; PHI 7d, REI 12h, Groups 9 & 12. Apply at planting as in-furrow spray.
fludioxonil (Cannonball WG): 7.0 oz/A (0.5 oz/1,000 ft row); PHI 7d, REI 12h, Group 12. See label for application restrictions.
penthiopyrad (Fontelis): 16.0 to 24.0 oz/A; PHI 3d, REI 12h, Group 7.
tebuconazole (Orius 3.6F): 20.5 fl oz/A; PHI 7d, REI 12h, Group 3. Apply in a 4- to 6-inch band into/over each furrow. May also be applied by chemigation. Dry bulb onion only.
thiophanate methyl (Topsin 4.5 FL): 40 fl oz/A; REI 72h, Group 1. Apply in furrow. Do not apply more than once per year.

Disease Control

Onion, Scallion, and Shallot Insect Control

Onion, Scallion, and Shallot Insect Control ashahane Wed, 05/29/2024 - 09:18

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

NOTES: For the insecticides listed below, one product trade name and formulation is provided for each active ingredient (AI) as an example of rates, preharvest interval (PHI), restricted entry interval (REI), and special instructions. In many cases, there are other products available with the same AI. Please see Table 27 and Insecticides Alphabetically Listed by Trade Name for more information on these insecticides.

The designation (Bee: L, M, or H) indicates a bee toxicity rating of low, moderate, or high. See the Protecting Honeybees and Native Pollinators section for more details.

The symbol * indicates a product is a restricted use pesticide. See Pesticide Safety and Use for more details.

The symbol ^OG indicates a product is listed by the Organic Materials Review Institute (OMRI) as approved for use in organic production. See Organic Certification section for more details.

Allium Leafminer (Phytomyza gymnostoma)

For more information on this pest and for cultural and chemical controls, see Allium Leafminer in the leek section.

abamectin (Agri-Mek* SC): 1.75 to 3.5 fl oz/A; PHI 7d for fresh or green onions and shallot leaves, 30d for onion and shallot bulbs, REI 12h, Bee: H, Group 6. Make 2 consecutive applications then rotate to a different mode of action. Make at least 2 consecutive applications of another mode of action before making additional Agri-Mek SC applications. Insect control can be reduced if used with a sticker or binder type product.
azadirachtin (Azatin O^OG): 4 to 16 oz/A foliar or drench, 4 to 16 oz/100 gal in greenhouses; PHI 0d, REI 4h, Bee: L, Group UN. When using lower rates, combine with adjuvant for improved spray coverage and translaminar uptake.
cyantraniliprole (Exirel): 13.5 to 20.5 fl oz/A; PHI 1d, REI 12h, Bee:H, Group 28. Use with an adjuvant to maximize efficacy. Spreading and penetrating adjuvants can cause negative crop response.
cyromazine (Trigard): 2.66 oz/A; PHI 7d, REI 12h, Bee: H, Group 17. Apply when leafminers first appear. Do not apply more than 6 times or 1 lb/A per calendar year.
dinotefuran (Scorpion 35SL): 5.25 to 7 fl oz/A foliar, 8.75 to 10.5 fl oz/A soil.; PHI 1d, REI 12h, Bee: H, Group 4A. Do not apply more than a total of 10.5 fl oz/A per season.
gamma-cyhalothrin (Declare*): 0.77 to 1.28 fl oz/A; PHI 14 days, REI 24h, Bee: H, Group 3A. Bulb onion only.
Isaria fumosorosea Apopka Strain 97 (PFR-97 20% WDG^OG): 1 to 2 lbs/A; PHI 0d, REI 4h, Bee: M, Group M.
lambda-cyhalothrin (Warrior* II): 0.96 to 1.6 fl oz/A; PHI 14d, REI 24h, Bee: H, Group 3A. Onion only.
mineral oil (SuffOil X^OG): 1 to 2 gal/100 gal water; PHI 14d, REI 4h, Bee: L, Group M. Onion only.
permethrin (Pounce* 25WP): 16.4 to 19.2 fl oz/A; PHI 1d, REI 12h, Bee: H, Group 3A. Onion only.
pyrethrins (Pyganic EC5.0II^OG): 4.5 to 17 oz/A; 0.25 to 0.50 oz/gal, 3 gal/1000 sq ft in greenhouse for backpack sprayers; PHI 0d, REI 12h, Bee: M, Group 3A.
spinetoram (Radiant SC): 6 to 10 oz/A; PHI 1d, REI 4h, Bee: M, Group 5. Efficacy improves with the addition of an adjuvant. Do not make more than 2 consecutive applications of Group 5 insecticides. Do not make more than 5 applications per year per crop.
spinosad (Entrust SC^OG): 4 to 8 oz/A; PHI 1d, REI 4h, Bee: M, Group 5. Use adjuvant for better control. Do not make more than 2 consecutive applications of Group 5 insecticides. Do not make more than 5 applications per year per crop.
thiamethoxam (Cruiser 70 WS): 0.05 to 0.2 mg/seed; Bee: H, Group 4A. Dry bulb onions only.
zeta-cypermethrin (Mustang*): 2.4 to 4.3 fl oz/A; PHI 7d, REI 12h, Bee: H, Group 3A.

Bulb Mites

Two genera of mites are known to infect species of Allium. The dry bulb mite (Aceria tulipae) is an eriophyid mite that survives on cultivated Allium species. Bulb mite species in the genus Rhizoglyphus can also be troublesome on alliums. Bulb mites overwinter in soil on debris, stored onions and garlic, and in garlic seed pieces. They are moved from field to field with soil on equipment, boots, etc., and planting infested garlic They are particularly troublesome in storage, causing desiccation and creating wounds that allow for entry of pathogens.

Bulb mites are favored by mechanical injury, disease, cool soil temperatures, and soils with high organic matter content. Avoid adding manure and use fallow periods to eliminate crop residue. In smaller plantings, removing culls from the field immediately after harvest will reduce overwintering populations. Dark plastic mulch will increase soil temperatures and control mites. Plant clean seed and rotate out of alliums for at least 4 years after an infestation. Avoid planting alliums directly after brassicas, corn, grain, or grass cover crops.

Cutworms

Cutworms are caterpillars that hide under the soil surface adjacent to the plant during the day and feed on leaves after dark. For best results, make application between midnight and dawn while cutworms are feeding aboveground. Synthetic pyrethroids may work best during cool spring weather. All synthetic pyrethroid restricted use (*) insecticides listed to control thrips on onions are also registered to control cutworm on this crop. See cutworms in the Pepper and Tomato (Outdoor) sections for more information on black and variegated cutworms.

Bacillus thuringiensis aizawai (XenTari^OG): 0.5 to 1.5 lb/A; PHI 0d, REI 4h, Bee: L, Group 11. Must be ingested. Apply in evening or early morning, before larvae are actively feeding. Adherence and weather-fastness will improve with use of an approved spreader-sticker. Use high rate at cool temperatures. For resistance management, may be rotated with Bt kurstaki products (Dipel).
Bacillus thuringiensis kurstaki (Dipel DF^OG): 0.5 to 2 lb/A; PHI 0d, REI 4h, Bee: L, Group 11. Must be ingested. Apply in evening or early morning, before larvae are actively feeding. Adherence and weather-fastness will improve with use of an approved spreader-sticker. Use high rate at cool temperatures. For resistance management, may be rotated with Bt aizawai products (XenTari).
Burkholderia spp. strain A396 (Venerate XC^OG): 1 to 4 qt/A; PHI 0d, REI 4h, Bee: M, Group UN.
Chromobacterium subtsugae strain PRAA4-1 (Grandevo^OG): 1 to 3 lb/A; PHI 0d, REI 4h, Bee: M, Group UN.
gamma-cyhalothrin (Declare*): 0.77 to 1.28 oz/A; PHI 14d, REI 24h, Bee: H, Group 3A.
lambda-cyhalothrin (Warrior* II): 0.96 to 1.60 oz/A; PHI 14d, REI 24h, Bee: H, Group 3A.
methomyl (Lannate* LV): 3 pt/A; PHI 7d, REI 48h, Bee: H, Group 1A. Add wetting agent to improve coverage. Black and variegated cutworm only. Dry and green onions only.
spinosad (Seduce^OG): 20 to 44 lb/A or 0.5 to1 lb/1000 sq ft.; PHI 1d, REI 4h, Bee: M, Group 5. Spread bait on soil around plants.
zeta-cypermethrin (Mustang*): 2.24 to 4 oz/A; PHI 7d, REI 12h, Bee: H, Group 3A.

Leek Moth (Acrolepiosis assectella)

For more information on this pest and for cultural and chemical controls, see Leek Moth in the leek section.

Onion Maggot (Delia antiqua)

Infestations may reduce young plant stands, cause plants to wilt and yellow, or damage bulbs. There are 3 generations each year. Effective control of the first generation (mid-May to June), which causes the most destruction, and minimizing mechanical and chemical damage to onions throughout the season, will reduce or eliminate damage by later generations. Rotate crops to keep maggot populations low; greater distances are more effective. Cumulative growing degree days (GDD) can be used to monitor the activity of onion maggot fly in your area: peak flight for the first generation is at 735 GDD, base 40°F. Delay planting until after first flight is finished and soil temperatures are high enough to kill eggs (95°F). Planting in late May is more likely to be safer than the first half of May. Cover recently seeded or transplanted crops with floating row covers as a barrier against onion maggot flies, placing the cover as soon as the transplants are set. Gathering culls into deep piles will limit reproduction to surface layers and reduce populations more than deep plowing or harrowing after harvest. Biological controls, including naturally occurring fungal pathogens, predaceous ground beetles, and soil applications of the entomopathogenic nematode Steinernema feltiae can all reduce onion maggot numbers. Nematodes can be applied to transplants, in transplant water, or as a post-transplant drench. Rates of 100,000-125,000 infective juveniles per transplant have been shown to be needed to achieve reduction in damage. Nematodes need a moist soil environment to survive. If using an insecticide, soil drench applications targeting the seed furrow or base of transplants, using at least 100-200 gal of water per acre to help the insecticide penetrate the root zone, are the most effective.

diazinon (Diazinon* AG500): 2 to 4 qt/A; REI 3d, Bee: H, Group 1B. Broadcast and incorporate just before planting. Will not control organophosphate-resistant onion maggots. Do not make more than one application per year. Bulb and green onion only.

Onion Thrips (Thrips tabaci)

Onion thrips range in color from yellow to black and are only 1/16" in length. They spend the winter as adults in crop remnants, alfalfa, wheat, greenhouses, and weeds along the border of crop fields. Thrips have rasping mouth parts which they use to tear open plant cells and feed on inner juices. Feeding occurs in protected areas between leaves. Damage may appear as silver lines, white patches, tip dieback and curling, slowed growth, reduced bulb size and yields, or result in plant death. Populations are favored by hot, dry weather. Plants are most sensitive when bulbs are forming and still small. Heavy rain or overhead irrigation can lower populations quickly. Lacewing larvae, pirate bugs, and predatory thrips are important natural enemies. Reduce populations by cleaning up crop residue after harvest to limit overwinter sites. Do not plant onions near alfalfa, clover, cucurbits or brassica crops that can harbor large populations of thrips, which may migrate to onions when these crops are cut or harvested.

Reflective mulch will repel colonizing thrips by confusing invading insects and preventing them from finding their host plants.

Scout plants along field margins where infestations build early. Begin applications when damage is first noticed or when there are 3 or more thrips per leaf. Repeat applications at 7- to 10-day intervals. Three to 6 applications may be necessary, but rotate between insecticide groups after 2 applications to help prevent development of resistance. Use a shorter interval in hot weather. Use spreader-sticker for better coverage. Apply in early evening, using high pressure and 100 gal water/A for best results.

acetamiprid (Assail 30SG): 5 to 8 oz/A; PHI 7d, REI 12h, Bee: M, Group 4A.
azadirachtin (Azatin O^OG): 4 to 16 oz/A foliar or drench, 4 to 16 oz/100 gal in greenhouses; PHI 0d, REI 4h, Bee: L, Group UN. When using lower rates, combine with adjuvant for improved spray coverage and translaminar uptake.
Beauveria bassiana (Mycotrol ESO^OG): 0.25 qt to 1 qt/A; PHI 0d, REI 4h, Bee: L, Group UN. Treat when populations are low and thoroughly cover foliage. Takes 7-10 days after the first spray to see control. Repeat applications may be needed.
Burkholderia spp. strain A396 (Venerate XC^OG): 2 to 4 qt/A; PHI 0d, REI 4h, Bee: M, Group UN. Suppression only.
Chenopodium extract (Requiem EC): 1.5 to 4 qts/A; PHI 0d, REI 4h, Bee: L, Group UN. Begin application as soon as thrips are seen. Thoroughly cover foliage.
Chromobacterium subtsugae strain PRAA4-1 (Grandevo^OG): 2 to 3 lb/A; PHI 0d, REI 4h, Bee: M, Group UN.
cyantraniliprole (Exirel): 13.5 to 20.5 oz/A; PHI 1d, REI 12h, Bee: H, Group 28. Suppression only. For best performance, use with an effective adjuvant.
deltamethrin (Delta Gold*): 1.5 to 2.4 oz/A; PHI 1d, REI 12h, Bee: H, Group 3A.
gamma-cyhalothrin (Declare*): 1.02 to 1.54 oz/A; PHI 14d, REI 24h, Bee: H, Group 3A.
imidacloprid (Admire Pro): 14 oz/A; PHI 21d, REI 12h, Bee: H, Group 4A. Soil applications only.
kaolin (Surround WP^OG): 25 to 50 lb/A or 0.25 to 0.5 lb/gal; PHI 0d, REI 4h, Bee: L. Suppression/repellence only. Good coverage into plant crown is essential. Generally compatible as a tank mix with other insecticides.
lambda-cyhalothrin (Warrior* II): 1.28 to 1.92 oz/A; PHI 14d, REI 24h, Bee: H, Group 3A.
malathion (Malathion 57EC): 1.5 pt/A onion, 1.5 to 1 pt/A shallot; PHI 3d, REI 12h onion, 24h shallot, Bee: H, Group 1B.
Metarhizium anisopliae Strain F52 (Met 52 EC): 40 to 80 oz/100 gal (drench), 8 to 64 oz/A (foliar); PHI 0d, REI 4h, Bee: L, Group UN.
methomyl (Lannate* LV): 3 pt/A; PHI 7d, REI 48h, Bee: H, Group 1A. Add wetting agent to improve coverage. Begin application before populations reach 3-5 thrips per plant. Green and dry bulb onions only.
permethrin (Pounce* 25WP): 9.6 to 19.2 oz/A; PHI 1d, REI 12h, Bee: H, Group 3A. Dry bulb onions only.
petroleum oil (Suffoil X^OG): 1 to 2 gal/100 gal water; PHI 0d, REI 4h, Bee: L.
pyrethrin (PyGanic EC5.0^OG): 4.5 to 17 oz/A; 0.25 to 0.50 oz/gal, 3 gal/1000 sq ft in greenhouse for backpack sprayers; PHI 0d, REI 12h, Bee: M, Group 3A.
pyriproxyfen (AX Pyriproxyfen 0.86EC): 8 oz/A; PHI 3d, REI 12h, Bee: L, Group 7D. Suppression only.
sodium tetraborohydrate decahydrate (Prev-AM): 100 oz/100 gal; REI 12h, Bee: L, Group 25. Do not apply in midday sun or mix with copper, sulfur, or oils.
spinetoram (Radiant SC): 6 to 10 oz/A; PHI 1d, REI 4h, Bee: M, Group 5. Thorough coverage is essential. Efficacy improves with the addition of an adjuvant.
spinosad (Entrust SC^OG): 4 to 8 oz/A; PHI 1d, REI 4h, Bee: M, Group 5. Suppression only. Use adjuvant for better control.
spirotetramat (Movento): 5 oz/A; PHI 3d, REI 24h, Bee: M, Group 23. Must be tank-mixed with a spray adjuvant with spreading and penetrating properties to maximize leaf uptake and sytemicity. Don't use sticker adjuvants. Controls immature stages, may also reduce adult fertility.
zeta-cypermethrin (Mustang*): 2.88 to 4 oz/A; PHI 7d, REI 12h, Bee: H, Group 3A.

Insect Control

Onion, Scallion, and Shallot Weed Control

Onion, Scallion, and Shallot Weed Control ashahane Wed, 05/29/2024 - 09:17

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

NOTES: For the herbicides listed below, one product trade name and formulation is provided for each active ingredient along with preharvest interval (PHI), restricted entry interval (REI), resistance management group number, and example of rates and special instructions. In many cases, there are other products available with the same active ingredient. However, not all products with the same active ingredient are registered for use in a crop. Always check the product label to be sure that the crop is listed before using.

Stale Seedbed

See Stale Seedbed Technique for information on the use of these herbicides or flaming.

glyphosate (Roundup Power Max): PHI 14d, REI 4h, Group 9.
paraquat (Gramoxone SL 2.0*): REI 12h or 24h, Group 22. *Restricted use: Applicators must complete an EPA-approved paraquat training every 3 years: https://www.epa.gov/pesticide-worker-safety/paraquat-dichloride-training-certified-applicators.
pelargonic acid (Scythe): PHI 1d, REI 12h, Group 0.

Preemergent Herbicides (before weeds germinate)

bensulide (Prefar 4E): REI 12h, Group 0. Dry bulb onion and dry bulb shallot only. Apply 5-6 lbs/A per application, only 1 application per year. Incorporate 1-2” into the soil with shallow cultivation or water through irrigation or rainfall within 36 hours of application. Only apply to onions growing in fine textured soil with good water drainage where the soil salinity value is less than 4 EC and soil temperature is between 55-75°F.
dimethenamid (Outlook): PHI 30d, REI 12h, Group 15. Apply 8-21 oz/A per application, up to 2 applications allowed per year, a minimum of 14 days apart. Do not exceed 21 oz/A per year. Use the lower rate on sandy soils and the higher rate on silt and clay soils. Apply to onion that has at least 2 fully expanded leaves or significant crop damage may occur. If applying to transplants, do not apply until transplants are in the ground and have had several days to recover.
s-metolachlor (Dual Magnum): REI 24h, Group 15. MA, ME, and NH only. Make sure the label for your state is available for download before using this product. This is a restricted label available only to growers who apply through the website www.syngenta-us.com/labels/indemnified-label-login and agree to a waiver of liability. Main target weeds for this registration are galinsoga and yellow nutsedge. All label instructions will be supplied after the application for use is completed.
pendimethalin (Prowl H2O): PHI 45d, REI 24h, Group 3. Apply 1.5-3.2 pts/A per application, up to 2 applications allowed per year. Do not exceed 3.2 pts/A per year. Apply as a broadcast treatment when onions have 2-9 true leaves. May be applied to direct-seeded and transplanted dry bulb onions. May be applied in the fall or spring to furrow area of land bedded in the fall in preparation for planting. Band apply and keep Prowl away from the area where dry bulb onion seed will be planted. Harrow off tops of beds after Prowl furrow application before planting dry bulb onions. Can also apply as a banded application to flag-leaf dry bulb onions. Only apply once to the furrow area and once to the dry bulb onion row per season. Rate based on soil texture.
trifluralin (Treflan HFP): PHI 60d, REI 12h, Group 3. Apply 0.75-1 pt/A per application, only 1 application per year. Apply between rows at layby, after onions have emerged. Emerged weeds should be removed prior to application. Avoid applying directly to the tops or exposed bulbs of onions. Incorporate uniformly into the soil between the onion rows. Two incorporation passes are required, the first within 24 hours of application, the second at least 5 days after the first. Avoid covering onions with treated soil. Rate based on soil texture, percent organic matter, and weed composition. Applications made to stressed onions may lead to crop damage and reduced yields.

Pre- and Postemergent Herbicides

bromoxynil (Broclean): PHI 30d, REI 24h or 48h, Group 24. Dry bulb onions only. Apply 1-1.5 pts/A per application, only 1 application per year. On muck soils with >10% organic matter Broclean must be applied 3-4 days before crop emergence. Rainfall or irrigation 2 days after application or 3 days before crop emergence may result in crop damage. If not on muck soils, can be applied after crop emergence with at least 50-70 gal/A of spray because concentrated Broclean will kill onions. If the waxy coating on onion leaves is insufficient, Broclean can kill onions. Dry soil, dry onion foliage, high light intensity, low humidity, and high temperatures help develop a waxy coating. Do not add a surfactant.
oxyfluorfen (Goal 2 XL): PHI 45d, REI 48h, Group 14. Dry bulb onions only. Apply 2-4 oz/A per application multiple applications allowed per year. Do not exceed 2 pts/A per year. For transplanted onions, may be applied to the soil before planting. The soil surface should be free of excessive plant residue before applying. For direct-seeded onions, may be applied when the onions have at least 3 fully developed true leaves and weeds are at the 2- to 4- leaf stage. A chlorotic band around some of the leaves may be observed, especially in cool wet conditions.

Postemergent Herbicides (after weeds germinate)

carfentrazone (Aim EC): PHI 0d, REI 12h, Group 14. Apply 0.5-2 oz/A per application, multiple applications allowed per year. Do not exceed 6.1 oz/A per season. Can be applied as a preplant burndown no later than 30 days before planting by seed. Can also be applied to row middles of emerged crops with hooded sprayers to control emerged weeds. Prevent any spray from contacting the crop, or injury will occur. For best results, make application to actively growing weeds up to 4” tall and rosettes less than 3” across.
clethodim (Select Max): PHI 45d, REI 24h, Group 1. Apply 6-32 oz/A per application, up to 4 applications per year, a minimum of 14 days apart. Do not exceed 64 oz/A per year. Apply to actively growing grasses. Add 0.25% v:v nonionic surfactant (1 qt/100 gal of spray). Can also be applied as a spot-spray by mixing 0.33-0.66% (0.44-0.85 oz/gal) Select Max and 0.25% v:v nonionic surfactant (0.33 oz/gal). Spray to wet, but do not allow runoff of spray solution.
fluazifop (Fusilade DX): PHI 45d, REI 12h, Group 1. Apply up to 24 oz/A per application, up to 2 applications allowed per year, a minimum of 14 days apart. Do not exceed 48 oz/A per year. Apply to actively growing grasses (see product label for susceptible stage). Add either crop oil concentrate (0.5-1%, 0.5-1 gal/100 gal of spray) or nonionic surfactant (0.25-0.5%, 1-2 qt/100 gal of spray).
glyphosate (Roundup Power Max): PHI 14d, REI 4h, Group 9. Apply 10 oz to 3.1 qts/A per application, multiple applications allowed per year. Do not exceed 5 qts/A per year. Rate based on target weed species. Can be applied during fallow intervals, prior to planting or transplanting, at planting, or before crop has emerged. Could cause injury when applied prior to transplanting or direct-seeding into plastic mulch. Remove residual product from plastic mulch with a 0.5” of water through irrigation or rainfall prior to planting.
paraquat (Gramoxone SL 2.0*): PHI 60d, REI 12h or 24h, Group 22. Apply 1.3-2.7 pts/A per application. For bulb onions 1 application may be made before crop emergence, and 1 may be made after crop emergence a minimum of 7 days apart. Do not exceed 4 pts/A per year. For seeded onion only 1 application allowed per year. Do not exceed 2.7 pts/A per year. Use precision directed spray application equipment adjusted to prevent spray contact with crop plants is applying after crop emergence. May be fatal if swallowed or inhaled. *Restricted use: Applicators must complete an EPA-approved paraquat training: https://www.epa.gov/pesticide-worker-safety/paraquat-dichloride-training-certified-applicators.
pelargonic acid (Scythe): PHI 1d, REI 12h, Group 0. Apply a 3-10% solution (3-10 gal/100 gal of spray). Rate based on target weed species. Apply in 75-200 gal/A of spray or with a spot sprayer until foliage is wet but not to the point of runoff. Repeat applications as necessary. Can apply for vegetative burndown during site preparation, prior to crop emergence from soil, as a directed and shielded spray during crop growth taking care to avoid contact with foliage and green tissue of crops, or as a harvest aid and desiccant to remove crop leaves or ease harvest.
sethoxydim (Poast): PHI 30d, REI 12h, Group 1. Apply 1.5 pt/A per application, multiple applications allowed per year. Do not exceed 4.5 pts/A per year. Apply to actively growing grasses. Use with crop oil concentrate (2 pt/A) or methylated seed oil (1.5 pt/A). Crop oil can cause injury under hot and humid conditions. Can also be applied as a spot-spray by mixing 1-1.5% (1.3-1.9 oz/gal) Poast and 1% v:v crop oil concentrate (1.3 oz/gal). Spray to wet, but do not allow runoff of spray solution.

Weed Control