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Midwest Vegetable Production Guide for Commercial Growers 1998

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Sweet Corn

Sugar-Enhanced (se) and Shrunken (sh2) or Supersweet Sweet Corns

There are three major types of sweet corn. These types vary in their sweetness, keeping quality after harvest, and cold soil vigor. Each type is available in yellow, bi-color, and white varieties.

Standard (su) sweet corn often does better than the other types in cold soils. Typically, it is not as sweet as the other types, and the sugar content declines rapidly after harvest. Standard sweet corn is grown today primarily for processing, for early fresh market sweet corn, and for specialized markets.

Sugar-enhanced (se) sweet corn has a higher sugar content and is more tender than standard sweet corn. These types are grown primarily for direct retail sales and local wholesale markets.

Supersweet (shrunken-2 or sh2) sweet corn has a higher sugar content than standard sweet corn. The sugar content does not decline rapidly after picking, so the corn remains sweet for several days after harvest. These types are grown primarily for wholesale shipping markets and local fresh market. The seed of these varieties is smaller and lighter than seed of normal corn, and typically does not do well in cold soil. For best results, do not plant until soil temperature reaches 60°F. Uneven stands and nonuniform emergence are relatively common.

Isolation Requirements

All sweet corn types should be isolated from field corn pollen by a distance of 250 ft., or by a tasseling date of 14 days.

Supersweet (sh2) varieties must be isolated from standard (su) and sugar-enhanced (se) types by a distance of 250 ft., or by a tasseling date of 14 days. If not isolated, kernels of both varieties will be starchy instead of sweet.

It is not essential to isolate sugar-enhanced (se) sweet corn from standard sweet corn: cross-pollination will not result in starchy kernels. However, isolation will permit the full expression of the sugar-enhanced traits.

To maintain purity of color, white corn should be isolated from yellow or bi-color corn. Pollen from yellow or bi-color corn will cause some yellow kernels in white varieties. Pollen from yellow corn will lead to extra yellow kernels in bi-color varieties. Pollen from white corn will not affect yellow or bi-color varieties.

Recommended Sweet Corn Varieties

Sugar-enhanced (se) Supersweet (sh2)
Yellow Maturity Yellow Maturity
Legend Early Bandit for trial
Amaize 2nd Early Challenger 2nd Early
Sweet Riser for trial Saturn 2nd Early
Incredible Main Endeavor 2nd Early
Tuxedo Main Krispy King 2nd Early
Sugar Ace Main Victor 2nd Early
Bi-color   Illini Gold Main
RXB 6201 for trial Zenith Main
Crystal Bell   Bunker Hill Main
Athos Early (Iowa only) Bi-Color  
Sweet Chorus Early Candy Corner 2nd Early
Temptation Early Everprime 2nd Early
Double Gem 2nd Early Festival 2nd Early
Polo 2nd Early Seneca Appaloosa for trial
Lancelot Main Candy Store Main
Delectable Main Crisp 'n' Sweet 730 Main
Precious Gem Main Phenomenal Main
White   Quest for Iowa
Alpine Main Autumn Star for Iowa
Seneca Sensation for trial White Maturity
Silver King for trial Silver Xtra Sweet Main
    Even Sweeter Main
Standard (su)
Yellow Maturity
Seneca Horizon Early
Rival (processing)  
White  
Silver Queen Main-Late

Spacing and Seeding

Rows: 30 to 40 in. apart. Plant early varieties 8 to 10 in. apart in the row, late varieties 9 to 12 in. apart in the row.

Seed: 10 to 15 lb. per acre.

Fertilizing

Lime: To maintain a soil pH of 6.0 to 6.5.

Preplant: N, 60 lb. per acre; P2O5, 0 to 100 lb. per acre; K2O, 0 to 150 lb. per acre. Adjust according to soil type, previous management, and soil test results for your state. For early season varieties, apply a starter fertilizer at planting. Do not exceed 80 to 100 lb. of N + K2O per acre in the fertilizer band (2 inches to the side of the row and 2 inches below the seed). A good starter fertilizer would be 200 lb. per acre of 6-24-24 or 10 gal. of 10-34-0 or similar analysis. On sandy soils, broadcast 30 lb. or band 15 lb. sulfur per acre.

Sidedress N: For loam or finer textured soils, apply 30 to 40 lb. N per acre when plants are 4 to 5 inches tall but before they are 10 inches in height. If the soil organic matter content exceeds 3% and/or sweet corn follows a legume, this sidedressed N application could be skipped provided excessive rainfall has not occurred. For irrigated sandy loam soils along river areas, the N preplant application should be replaced with two sidedressings of approximately 40 lb. N per acre each: one when 4 to 5 inches tall (4 to 5th leaf) and the other at 10 inches in height (10 to 12 leaf).

Diseases Controlled Treatment Comments
Seed rot and damping off Captan 50W at 1 tsp. per lb. of seed. Most seed companies deliver pretreated seed.
Rust Plant rust resistant hybrids. Comet, Jubilee, Incredible, Sweetie 82, and many others.
  Tilt at 4 fl. oz. per acre. Begin applications when rust pustules first appear. Repeat at 7-14 day intervals. Do not apply more than 16 fl. oz. per acre per season. 14 day PHI.
  Bravo, Terranil, or Echo at 0.75 to 2 pt. per acre for flowable (F) formulations or 0.63 to 1.5 lb. per acre for dry (WP, DF, or DG) formulations. Do not apply to sweet corn to be processed.
or
Begin applications when conditions favor disease development. Repeat at 4-7 day intervals, beginning before tassel emergence and ear formation. Do not feed treated forage to livestock. 14 day PHI.
  Dithane, Manzate, Penncozeb, or Manex II at 1.5 lb. per acre for dry (WP, DF, or DG) formulations or 2.4 pt. per acre for flowable (F) formulations. See comments for Bravo. 7 day PHI.
Smut Use tolerant hybrids such as Apache, Bellringer, Commanche, Comet, Gold Cup and Merit.  
Stewart's wilt Plant wilt resistant hybrids. Apache, Comet, Comanche, Gold Cup, Incredible, Sweet Sue, Seneca Sentry, Miracle, How Sweet It Is.
  Use an insecticide to control flea beetles. Especially on more susceptible hybrids following a mild winter.
"Helminthosporium" leaf blights, and anthracnose Plant resistant varieties. Follow a 2-3 year plan. Begin applications when disease first appears. Repeat at 7-14 day intervals. Do not apply more than 16 fl. oz. per acre per season. 14 day PHI.
  Tilt at 2 to 4 fl. oz. per acre.  
  Bravo, Terranil, Echo at 0.75 to 2 pt. per acre for flowable (F) formulations or 0.63 to 1.5 lb. per acre for dry (WP, DF, or DG) formulations. Do not apply to sweet corn to be processed.
or
Begin applying fungicides at the first sign of disease. Apply at 4-7 day intervals, or as needed to maintain control. Do not feed treated forage to livestock. 14 day PHI.
  Dithane, Manzate, Penncozeb, or Manex II at 1.5 lb. per acre for dry (WP, DF, or DG) formulations or 2.4 pt. per acre for flowable (F) formulations. Begin applying fungicides at the first sign of disease. Apply at 4-7 day intervals, or as needed to maintain control. Do not feed treated forage to livestock. 7 day PHI.
Maize dwarf mosaic, chlorotic dwarf, and wheat streak mosaic Plant resistant or tolerant varieties. Bi-Guard, HMX8396, HMX9352S, Silverett, Sundance, WH3443.
  Control Johnsongrass and volunteer wheat.  
Herbicide* Treatment** Comments
Preemergence    
Aatrex or others 4L, 80W, Nine-0 1 qt. on light-colored soils, 1 to 2 qt. on darker soils, of 4L, 1.25 to 1.5 lb. per acre of 80W or 1.1 to 2.2 lb. per acre of Nine-0. Apply at planting time or before corn emerges. Caution: Atrazine remains in the soil and may carryover and injure susceptible crops sown in the fall or following spring - tomatoes, cucumbers, melons, etc. - consult label for suggested rotational crops. Not effective on muck soils. RUP.
Bladex 4L or 90DF 1.3 qt. on light-colored soil, 3 qt. on darker colored soil with 4L; 1.3 to 3.3 lb. per acre of 90DF. Apply immediately after planting. Supersweet (sh2) corn may be injured by Bladex. RUP. Enclosed cab required.
Dual 8E 2 pt. on light-colored soils, 3 pt. on darker colored soils. Apply at planting time or before corn emerges. May be mixed with atrazine or Bladex. Use low rates of each herbicide in combinations.
Lasso 4E 2 qt. on light-colored soils, 3.25 qt. on dark colored soils. Apply at planting time or before corn emerges. May be mixed with atrazine or Bladex. Use low rates of each herbicide in combinations. RUP.
Eradicane Extra 6.7E 4 to 5.3 pt. per acre. Will suppress wild proso millet. Must be incorporated. Contains an extender that may lengthen the period of control.
Prowl 3.3E 1.8 to 4.8 pt. per acre. Illinois and Minnesota only. For processing varieties. Plant sweet corn at least 1.5 in. deep. Apply after planting corn and do not incorporate.
Frontier 6E 13 to 25 fl. oz. per acre. Apply preemergence for best activity. 50 day PHI.
Postemergence    
Aatrex, other (Atrazine) 1 to 1.5 pt. 4L per acre or 0.6 to 0.9 lb. of 80W or 0.55 to 0.83 lb. of Nine-0 plus 1 qt. COC per acre. Apply before weeds are 1.5 in. tall. Check all label precautions and replant restrictions. Total Atrazine used per year must not exceed 2.5 lb. a.i. per acre. RUP.
2, 4-D (4 lb./gal.) 0.5 to 0.75 pt. amine per acre. Apply after weeds are up. Most effective when weeds are small. Apply with straight boom sprayer if corn is small; do not apply when corn is 12 in. or taller. Avoid drift onto other vegetable crops.
Basagran 4L 0.75 to 1 qt. per acre on small emerged weeds. Repeat application at 7-10 days for yellow nutsedge if necessary. Do not apply to corn that has been subjected to stress because injury may result.
Gramoxone Extra 2.5E 0.8 pt. per acre plus 1 qt. nonionic surfactant per 100 gallons. Specialized equipment for directed spray required. Corn must be 10 inches tall from ground to top of whorl. Spray must reach no higher on corn than 3 in. above soil. Improper application can severely injure corn. RUP.
Accent 0.66 oz. 75DF per acre. Always add COC at 1% or non-ionic surfactant at 0.25%. Minnesota, Iowa, Illinois, and Wisconsin only. Use only on labeled varieties. Do not apply any organophosphate insecticide or other herbicide within 7 days before or 3 days after Accent application. Label restrictions apply.
Stale Seedbed    
Gramoxone Extra 2.5E 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. RUP.
Roundup Ultra (4 lb./gal.) 1 qt. per acre on small emerged weeds; 2 to 5 qt. per acre on perennial weeds. See label for specific weeds. Apply in 20 to 60 gal. water per acre on emerged weeds before the crop emerges. Does not provide residual control. Can be tank mixed with Lasso plus Aatrex in minimum tillage (see label).
*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
Seed corn maggot, seed corn beetle, wireworms Plant seed that has been treated with an insecticide prior to planting. Use either diazinon or a combination of diazinon and lindane. Follow label directions. Although most sweet corn seed has been treated with a fungicide, it is seldom treated with an insecticide to prevent seed and seedling damage.
Corn rootworms Aztec 2.1G at 6.7 oz. per 1000 linear ft. of row.
or

Counter 15G, Lorsban 15G, Thimet 15G at 8 oz. per 1000 linear feet of row.
or

Counter 20CR or Thimet 20G at 6 oz. per 1000 linear feet of row.
or
Apply any of these in a 7 in. band over the row and behind the planter shoe in front of the press wheel.
  Dyfonate II 10G or Mocap 10G at 12 oz. per 1000 linear feet of row.
or

Fortress 2.5G at 6 oz. or 5.0G at 3 oz. per 1000 linear feet of row.
or

Force 3G at 3 to 5 oz. per 1000 linear feet of row.
DO NOT place Dyfonate, Lorsban, Mocap or Thimet in the furrow or in direct contact with the seed.
  Other corn rootworm control considerations:

1. If few or no rootworm beetles were present in the field the previous year, then there is little chance of a damaging infestation.
2. If sweet corn was grown in the field the previous year and a regular spray schedule was followed during silking, then there is little chance of a damaging infestation.

Flea beetle Resistant varieties. Use varieties that are resistant to Stewart's wilt, which is vectored by the beetles. See page 113.
  Sevin XLR at 2 qt. per acre.
or
2 day PHI.
  Lorsban 4E at 2 to 3 pt. per acre.
or
35 day PHI.
  Asana XL at 5.8 to 9.6 fl. oz. per acre.
or
1 day PHI.
  Warrior 1EC at 2.6 to 3.8 fl. oz. per acre.
or
Do not exceed 3.84 pt. per acre per season. 1 day PHI.
  Ambush 2EC at 6.4 to 12.8 fl. oz. or 25WP at 6.4 to 12.8 oz. per acre.
or
1 day PHI.
  Pounce 3.2EC at 4 to 8 fl. oz. or 25WP at 6.4 to 12.8 oz. per acre. 1 day PHI.
Cutworms Lorsban 4E at 2 to 4 pt. per acre. Most effective when soil is moist. If ground is dry, cloddy, or crusty, shallow incorporation using a rotary hoe or other suitable equipment before or soon after treatment may improve control. 35 day PHI.
  Asana XL at 5.8 to 9.6 fl. oz. per acre.
or
1 day PHI.
  Warrior 1EC at 2.6 to 3.8 fl. oz. per acre.
or
Do not exceed 3.84 pts. per acre per season. 1 day PHI.
  Ambush 2EC at 6.4 to 12.8 fl. oz. or 25WP at 6.4 to 12.8 oz. per acre.
or
1 day PHI.
  Pounce 3.2EC at 4 to 8 fl. oz. or 25WP at 6.4 to 12.8 oz. per acre.
or
1 day PHI.
  Baythroid 2E at 0.8 to 1.6 fl. oz. per acre. 0 day PHI.
Corn leaf aphid Malathion 5EC or 57EC at 1.5 pt. per acre. Apply when less than 50% of the field is pollinated and more than 50% of the plants are infested with at least 50 aphids. 5 day PHI.
European corn borer Monitor with pheromone or blacklight traps. The most important spray for corn borer control is when green tassels have just begun to shoot.
  Warrior 1EC at 2.6 to 3.8 fl. oz. per acre.
or
Do not exceed 3.84 pts. per acre per season. 1 day PHI.
  Baythroid 2E at 1.6 to 2.8 fl. oz. per acre.
or
Do not exceed 10 applications per season. 0 day PHI.
  Penncap-M at 2 to 4 pt. per acre.
or
Not for corn earworms. 3 day PHI.
  Ambush 2EC at 6.4 to 12.8 fl. oz. or 25WP at 6.4 to 12.8 oz. per acre.
or
Do not apply more than 1.2 lb. a.i. of Ambush and/or Pounce per acre per season. 1 day PHI.
  Pounce 3.2EC at 4 to 8 oz. or 25WP at 6.4 to 12.8 oz. per acre.
or
 
  Lannate 90SP at 0.3 to 0.5 lb. or LV at 1 to 1.5 pt. per acre.
or
0 day PHI for ears, 3 days for forage. Not for corn earworms.
  Sevin XLR Plus at 2 qt. per acre. 2 day PHI.
Corn earworm Monitor with pheromone traps. Begin sprays when ears begin to silk and when pheromone traps show need. Stop sprays when more than 90% of silks are brown.
Threshold
More than 5 moths per night in pheromone trap and green silks are present.
Warrior 1 EC at 2.6 to 3.8 fl. oz. per acre.
or
Do not exceed 3.84 pts. per acre per season. 1 day PHI.
Baythroid 2E at 1.6 to 2.8 fl. oz. per acre.
or
Do not exceed 10 applications per season. 0 day PHI.
  Ambush or Pounce at same rates, restrictions and precautions as for European corn borer.
or
Do not apply more than 1.2 lb. a.i. of Ambush and/or Pounce per acre per season. 1 day PHI.
  Asana XL at 5.8 to 9.6 fl. oz. per acre.
or
Not for European corn borer. Do not exceed 0.5 lb. a.i. per acre per season. 1 day PHI.
  Sevin XLR Plus at 2 qt. per acre. 2 day PHI.
Fall armyworm Monitoring. Fall armyworms can be monitored with pheromone traps or by looking for damage to whorl-stage corn. Best time to treat is when tassels are just beginning to emerge. Don't wait until silks appear to control fall armyworm.
  Warrior 1 EC at 2.6 to 3.8 fl. oz. per acre.
or
Do not exceed 3.84 pts. per acre per season. 1 day PHI.
  Baythroid 2E at 2.8 fl. oz. per acre.
or
Do not exceed 10 applications per season. 0 day PHI.
  Ambush 2EC at 6.4 to 12.8 fl. oz. or 25WP at 6.4 to 12.8 oz. per acre.
or
Do not apply more than 1.2 lb. a.i. of Ambush and/or Pounce per acre per season. 1 day PHI.
  Pounce 3.2EC at 4 to 8 oz. or 25WP at 6.4 to 12.8 oz. per acre.
or
 
  Lannate 90SP at 0.5 lb., or LV at 1.5 pt. per acre.
or
0 day PHI for ears, 3 days for forage.
  Asana XL at 9.6 fl. oz. per acre. Do not exceed 0.5 lb. a.i. per acre per season. 1 day PHI.

Monitoring European Corn Borer and Corn Earworm

One of the keys to successfully managing corn borers and corn earworms on sweet corn is to be able to determine when the insects are active. European corn borers can be monitored effectively with blacklight traps and field observations and corn earworms can be monitored with pheromone traps. When moths are being caught in the traps it means that egg laying is taking place. Corn borer eggs are laid on the leaves, usually on the underside, in the region of the ear. The larvae will feed on the leaves and later may migrate to the ear, if one is present. Corn earworm moths lay their eggs directly on green silks. The young larvae that hatch out of those eggs will follow the silks down into the tip of the ear. Because the egg laying behavior of the two insects differ, the strategies for their control also differ. Corn borers can be controlled by spraying during the late whorl and tasselling stages as well as during the silking stage. The migrating larvae should contact a lethal dose of insecticide while moving to the ear zone. Corn earworms must be controlled by directing the sprays at the silks so that when the eggs hatch the young larvae will immediately contact the insecticide.

For corn borers, treat during the late whorl stage if 20% or more of the plants show larval feeding. The presence of large numbers of moths in the light trap is also justification for insecticidal treatment. One application during the late whorl stage followed by additional treatments every 5 days until just prior to harvest will usually provide adequate control. For corn earworms, treatment is justified if fresh green silks are present and moths are being caught in pheromone traps. In general, the higher the moths catches, the shorter the interval between sprays. If fewer than about 5 moths are being caught per night, a spray interval of 5 days should be adequate. As moth catches approach the level of 50-100 per night, a spray interval of 2-3 days would be more appropriate. The exact determination of the spray interval depends on many factors, including how much damage you can tolerate, the value of the crop, and the cost and effectiveness of the insecticide. Stop treating for corn earworms when 90% of the silks are brown.

Obviously, growers should not treat separately for these two pests. Some of the insecticides we recommend are effective against both species. Choose the insecticides that are more effective against the particular pest that is more prevalent at the time. If both pests are present, choose an insecticide that will adequately control both of them.


Indiana CropMAP     NewCROP

last update Friday, October 09, 1998 by aw