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Midwest Vegetable Production Guide for Commercial Growers 1998

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Onion (Bulb and Green)

Varieties

Bulb Early: Norstar, Cavalier, Comanche Main: Copra, Burgos, Lakota, Nitro, Spirit Late: Celtic, Sweet Sandwich, Spartan Banner 80, Crusader
Green Beltsville Bunching.

Spacing and Seeding

Raised beds with two double rows or wide rows spaced 14 in. apart on top of the bed with 12 seeds per foot within the wide (2 in.) row. Seed: 4 lb per acre.

Or transplant 4 in. apart in rows.

Fertilizing

Lime: Mineral soils: To maintain a soil pH of 6.0 to 6.8. Organic soils: lime if the pH is less than 5.2.

Preplant: N, for mineral soils, 70 lb. per acre with 1/2 broadcast preplant and 1/2 applied as a band 2 in. below the seed; organic soils: 100 lb. N per acre broadcast and disked in; P2O5, 25 to 250 lb. per acre; K2O, 0 to 250 lb. per acre. Adjust according to soil type, previous management, and soil test results for your state. At seeding, spray directly on the seed a solution of 2-6-0 at 1 pint per 100 ft. of linear row. A 2-6-0 solution is equivalent to a 1:5 dilution of 10-34-0 liquid fertilizer with water. On muck soils with a pH greater than 6.0, add 1 lb. of MnSO4 per 1000 ft. of row at seeding or use foliar Mn at the rate of 0.3 lb/100 gallons. Apply 2 to 3 times during the season starting 3 weeks after emergence.

Sidedress N: Mineral soils: 60 lb. N per acre to either side of the row at the four to five -week stage of growth or by June 1. Muck soils: no sidedress N needed unless heavy rain occurs.

Diseases Controlled Treatment Comments
Alternaria purple blotch and Botrytis leaf blight 3-4 year crop rotation. Rotation out of onions or related vegetables will reduce the threat of these diseases in future onion crops.
  Apply fungicides beginning when disease first appears:  
  Rovral 50W at 1.5 to 2 lb. per acre. 14 day spray interval.
or
0 day PHI.
  Bravo, Terranil, or Echo at 2 to 3 pt. per acre for flowable (F) formulations or 1.5 to 2.5 lb. per acre for dry (DF, DG) formulations.
or
Do not use Bravo on Spanish onions. 0 day PHI.
  Dithane, Manzate, Penncozeb or Manex II at 2 to 3 pt. per acre for flowable (F) formulations or 2 to 3 lb. per acre for dry (WP,DF,DG) formulations. 5 day PHI.
Downy mildew Ridomil GoldMZ at 1.5 to 2.0 lb. per acre. 14 day spray interval.
or
5 day PHI.
  Ridomil GoldBravo at 1.5 lb. per acre. 14 day spray interval.
or
0 day PHI.
  Bravo, Terranil, or Echo at 2 to 3 pt. per acre for flowable (F) formulations or 1.5 to 2.5 lb. per acre for dry (DF, DG) formulations.
or
Do not use Bravo on Spanish onions. 0 day PHI.
  Dithane, Manzate, Penncozeb or Manex II at 2 to 3 pt. per acre for flowable (F) formulations or 2 to 3 lb. per acre for dry (WP,DF,DG) formulations. 5 day PHI.
Fusarium basal rot Use Fusarium-resistant varieties such as Elba Globe, Spartan Banner, and Harvestmore. Consult seed catalogues for varietal characteristics.
Neck rot Windrow plants until neck tissues are dry before topping and storage. Cure rapidly and properly. Artificial drying may be necessary (forced heated air at 93-95½F for 5 days).
Herbicide* Treatment** Comments
Preemergence    
Dacthal 75WP 6 lb. on light-colored soils (less than 2% organic matter), 14 lb. on darker colored soils in at least 50 gal. water per acre. Apply immediately after seeding or transplanting, or after a clean cultivation and hand weeding. Use 50-mesh or larger screens. Not effective on muck soil. Can be used up to 14 weeks after planting.
Goal 2XL 1 to 2 pt. per acre. Transplants only. Apply after soil preparation and before transplanting. Do not use before direct-seeding onions. Dry bulb onions only.
Prowl 3.3EC 0.6 to 2.4 qt. per acre. Seeded or bulbs Muck soil: Apply 2 to 2.4 qt. per acre preemergence and after the 2 leaf stage. A third application can be made at the 6-9 leaf stage. Pack soil well over the row. Maximum application of 7.2 qt. per acre per year. Mineral soils: Apply 1.2 to 3.6 pt. per acre when onions have 2 to 9 leaves. Maximum application of 3.6 pt. per acre per year. 45 day PHI.

Transplants Apply after transplanting. Muck soil: 2 or 3 applications at 2 to 2.4 qt. per acre. Mineral soil: 1 or 2 applications at 1.2 to 3.6 pt. per acre. 45 day PHI.

Prefar 4E 5 qt. per acre on light-colored sandy soils (less than 1% organic matter), 6 qt. on other soils. Dry bulb only. Apply before planting and incorporate 1-2 inches, or apply after seeding and before crop emerges, and irrigate within 24 hours. Mineral soils only.
Postemergence    
Goal 2XL 8 fl. oz. per acre in 40 to 60 gal. of water per acre. Apply to direct-seeded onions after they have 2 true leaves. Up to 2 pt. per acre may be applied over transplanted onions within 2 days of transplanting. Spray during sunny warm weather. Do not exceed 2 pt. per acre per year (including applications before transplanting). Dry bulb only. 45 day PHI.
Buctril 2E 1 to 1.3 pt. per acre in 50 to 70 gal. water per acre if applied to emerged onions. Do not use surfactant. Apply 2 to 3 days before onions emerge, or when onions have 2 to 5 true leaves. Apply when soil and leaves are dry to prevent crop injury. Thorough coverage necessary.
Fusilade DX 2E 10 to 12 fl. oz. plus 1 pt. nonionic surfactant per acre. Apply to small, actively growing grasses. 45 day PHI. Dry bulb only.
Poast 1.5E 1 to 1.5 pt. plus 1 qt. nonionic surfactant per acre. Apply to actively growing grasses. Maximum of 4.5 pt. per acre per season. 30 day PHI.
Select 2EC 6 to 16 fl. oz. plus 1% COC per acre. Apply to actively growing grasses. Will kill bluegrass. Do not apply more than 32 fl. oz. per acre per season. 45 day PHI. Dry bulb onions only.
Stale Seedbed    
Gramoxone Extra 2.5EC 2 to 3 pt. per acre plus 1 pt. nonionic surfactant per 100 gallons spray solution. Apply to emerged weeds before or after seeding, but before crop emerges. 60 day PHI. RUP.
Roundup Ultra (3 lb./gal.) 2 to 3 qts. per acre. Apply before or after planting, but before crop emerges.
*For specific weeds controlled by each herbicide, check table on page 23.
**Rates given are for overall coverage. For band treatment, reduce amounts according to the portion of acre treated.
   
Insects Controlled Treatment Comments
Onion maggots For furrow treatment at planting:  
  Lorsban 4E at 1.1 fl. oz. per 1000 linear ft. of row as an in-furrow drench.
or
Use a minimum of 40 gal. of total drench per acre. One application per year.
  Dyfonate II 10G at 6 oz. per 1000 linear ft. of row as a furrow application.
or
Use only on soils containing 10% or more organic matter.
  Diazinon 14G at 7 lb. per acre as a furrow application.
or
May be used on dry or green onions.
  Diazinon AG500 at 1 qt. per acre. Planting time treatment only. Apply in sufficient water to drench seed furrow planting.
  Other recommended control procedures include: Remove cull onions after harvest, plant as far as possible from last year's onion fields, and avoid mechanical damage to onions (undamaged bulbs are more resistant to maggot damage).
Onion thrips Field site selection. Onion thrips can build to extremely high levels in small grains and will move to onions when the small grains dry down or are harvested. Try to avoid planting next to small grains.
Threshold
25 thrips per plant.
Resistant/tolerant varieties. Tolerant varieties include White Keeper, El Charro, Snow White, Vega, X201, and Zapotec
  Ammo 2.5EC at 4 to 5 fl. oz. per acre.
or
7 day PHI. Bulb onions only. Do not exceed 0.5 lb. a.i. per acre per season.
  Warrior 1EC at 2.6 to 3.8 fl. oz. per acre.
or
Do not exceed 1.92 pts. per acre per season. 14 day PHI.
  Fury 1.5E at 3.2 to 4.2 fl. oz. per acre.
or
7 day PHI. Bulb onions only.
  Mustang 1.5EW at 3.2 to 4.2 fl. oz. per acre.
or
7 day PHI. Bulb onions only.
  Diazinon AG500 at 1 pt. per acre.
or
14 day PHI. Use 100 to 200 gal. of water per acre for improved control.
  Guthion 2L at 2 to 3 pt. per acre.
or
Do not apply more than three times per season. 28 day PHI for dry bulbs, 14 days for green onions. Allow at least 7 days between applications for bulb onions, 10 days for green onions.
  Ambush 2EC at 9.6 to 19.2 oz. or 25WP at 9.6 to 19.2 oz. per acre.
or
Bulb onions only. Use when thrips first appear. Not for rescue treatments. 1 day PHI.
  Pounce 3.2EC at 6 to 12 oz. or 25 WP at 9.6 to 19.2 oz. per acre.
or
Bulb onions only. Use when thrips first appear. Not for rescue treatments. 1 day PHI.
  Lannate LV at 3 pt. per acre or 90SP at 1 lb. per acre.
or
7 day PHI.
  Penncap-M at 1 qt. per acre. 15 day PHI.


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last update Wednesday, October 07, 1998 by aw