As with many other major, sweet corn presents an ongoing management issue regarding weed control. For economy and efficiency, it is of utmost importance for farmers to view weed pests as a complex.
Specific plant pests which interfere with sweet corn production are both diverse and unpredictable in their colonization of fields. A specific plant or two may present more of a challenge for a period of time only to be
replaced by another dominant pest or a mixture of weeds with individually low populations.
Overall, thinking in terms of creating a good field management history is central to making decisions about
addressing the weed population presented during any specific year. Sweet corn production needs to be supported
by a balance involving intelligent cultural practices and modest
chemical weed control practices.
If farmers were to try to focus on one pest in isolation, they would lose their target; it is that essential to deal with
weeds as a complex. While they may feel an urge to focus on one major pest at one time or another, to limit
themselves to such treatments would more likely backfire when the complex of invaders made a resurgence after
a brief period of time. Thus, they expect to go for "the best shot" rather than a "perfect shot".
Beyond the obvious issue of pest presence, a farmer's decisions are strongly impacted by costs. Many farmers,
knowing that they can neither afford to apply herbicides for each and every significant plant pest nor expect
weed free fields, are strongly impacted by manufacturer's marketing strategies.
Common Weeds in Sweet Corn Crops
Common Name Scientific Name Life Cycle*
Monocots: Grasses and Grass-like Plants
Broadleaf Signalgrass Brachiaria platyphaylla A
Crabgrass, Large Digitaria sanguinalis A
Foxtail, Giant Setaria faberi A
Johnsongrass Sorghum halepense P
Fall Panicum Panicum dichotomiflorum A
Ryegrass, Italian Lolium multiflorum A
Shattercane Sorghum bicolor A
Dicots: Broadleaf Plants
Burcucumber Sicyos angulatus A
Cocklebur, Common Xanthium strumarium A
Milkweed, Honeyvine Ampelamus ambidus P
Morningglory, Bigroot Ipomoea pandurata P
Morningglory, Ivyleaf Ipomoea hederacea A
Pigweed, Smooth Amaranthus hybridus A
Pokeweed, Common Phytolacca americana P
Ragweed, Giant Ambrosia trifida A
Trumpetcreeper Campsis radicans P
*(A = annual, B = biennial, and P = perennial)
Controls
Biological: None available.
Cultural: Practice clean cultivation and destroy crop residues after harvesting.
Chemical
Application:
2,4-D (2,4-D or Weedar 64 4L): Application rate is 1 pt per acre or 4 lb per gallon per acre. Applied after corn and weeds emerge but before corn is 8 inches tall using ground spray. Avoid drift to sensitive crops, including
some supersweet (Sh2, SE) cultivars of sweet corn.
Alachlor (Lasso 4E or Micro-Tech 4 ME): Application rate is 2 to 4 qt / 2.5 to 3 qt per acre. Applied as preplant or preemergence by ground spray. Use higher rate for control of lambsquarters, black nightshade and
nutsedge. Restricted use pesticide.
Alachlor 2.5 to 3 + Cyanazine 1.2 to 1.6 (Lasso 4E + Bladex 80W or Bladex 4L): Application rate is 2 1/4 to 3 qt + 1 ½ to 2 lb per acre or 1.2 to 1.6 qt per acre. Applied as preplant or preemergence by ground spray.
Alachlor 2 + [Cyanazine 1.7 + Atrazine .8] (Lasso 4E + Extrazine 90 DF): Application rate is 2 qt + 2.8 lb per acre. Applied as preplant or preemergence by ground spray. Do not use if small grains or other crops are to be planted the same year or if other vegetable crops or tobacco are to be planted the next year. Sweet corn or popcorn can be planted the second year after land is treated. Follow mixing instructions carefully.
Alachlor 2.5 to 3 + Atrazine 1 to 1.5 (Lasso 4E + Atrazine 80W or Aatrex Nine O or Atrazine 4L w/
atrazine): Application rate is 2 1/4 to 3 qt +1 1/4 to 2 lb or 1.1 to 1.6 lb or 1 to 1 ½ qt per acre. Applied as preplant or preemergence by ground spray. Do not use if small grains or other crops are to be planted the same
year or if other vegetable crops or tobacco are to be planted the next year. Sweet corn or popcorn can be planted the second year after land is treated. Follow mixing instructions carefully.
Atrazine (AAtrex 4L): Application rate is 1 to 2 qt per acre. Applied after planting, but before weeds are 1 inch tall by ground spray. Do not plant any crop but corn or 18 months on land treated with 1 lb or more atrazine.
Follow mixing instructions closely. Best in combination with alachlor or metolachlor. Atrazine has been found in surface and ground water. It also injures vegetable crops planted after corn. Resistance to atrazine has occurred in certain weed species. Restricted use pesticide.
Bentazon (Basagran 4S): Application rate is 1 ½ to 2 pt per acre. Applied to small weeds by ground spray. Use 2 applications for nutsedge control. See label for precautions and rates of application and growth stage of plants to control specific weeds. Include 1 qt crop oil per acre.
Butylate + Atrazine (Sutan Plus 6.7E + Atrazine 80W or AAtrex Nine-O or Atrazine 4L): Application rate is 2.5 to 3.5 qt + 1 ½ to 2 lb or 1.3 to 1.8 lb or 1.2 to 1.6 qt per acre. Applied before planting by ground spray
and incorporated immediately. Note incorporation directions on label. Do not use if small grains or other crops are to be planted the following year. Sweet corn or popcorn can be planted the second year after land is treated
with these herbicides. Follow mixing directions carefully.
Butylate + Atrazine (Sutazine+):Application rate is 5 1/4 to 7 pt per acre. Applied before planting by ground spray and incorporated immediately. Note incorporation directions on label. Do not use if small grains or other
crops are to be planted the following year. Sweet corn or popcorn can be planted the second year after land is treated with atrazine. Follow mixing instructions carefully.
Butylate + Cyanazine (Sutan Plus 6.7E and Bladex 80W or Bladex 4L): Application rate is 3 1/4 to 4 1/4 pt + 2 to 2 ½ lb or 1 ½ to 2 qt per acre. Apply before planting by ground spray and incorporate immediately. Note
directions on label. Do not plant seed deeper than 2 inches.
Butylate + [Cyanazine + Atrazine] (Sutan + Extrazine 90 DF): Application rate is 3 2/3 pt + 2.8 lb per acre.
Apply before planting by ground spray and incorporate immediately. Note incorporation directions on label. Do not use if small grins or other crops are to be planted the following year. Sweet corn or popcorn can be planted
the second year after land is treated with atrazine. Follow mixing instructions carefully.
Cyanazine + Atrazine (Extrazine 90 DF): Application rate is 3.3 to 4.4 lb per acre. Apply as preplant or preemergent by ground spray. Do not use if small grains or other crops are to be planted the same year or if other
vegetable crops or tobacco are to be planted the next year. Sweet corn or popcorn can be planted the the second year after land is treated with these herbicides. Follow mixing instructions carefully.
Dimethenamid (Frontier 6 EC): Application rate is 1 to 2 pt per acre. Apply as preplant or preemergent by ground spray. Check label for rate adjustments for soil type. Controls many broadleaves and grasses.
Glyphosate (Roundup): Application rate is 1.5 to 3 qt per acre. Apply by ground spray. For stale seedbed preparation in reduced tillage systems.
Metholachlor + Atrazine (Bicep 4.5L or Bicep 6L): Application rate is 2.5 qt or 1.8 qt per acre. Apply as preplant or preemergent by ground spray. Do not use if small grains or other crops are to be planted the same
year or if other vegetable crops or tobacco are to be planted the next year. Sweet corn or popcorn can be planted the second year after land is treated with atrazine. Follow mixing instructions carefully.
Metolachlor + Atrazine (Dual 8E + Atrazine 80W or AAtrex Nine-O or Atrazine 4L): Application rate is 2 pt + 1 ½ to 2 lb or 1.3 to 1.8 lb or 1.2 to 1.6 qt per acre. Apply as preplant or preemergent by ground spray. Do
not use if small grains or other crops are to be planted the same year or if other vegetable crops or tobacco are to be planted the next year. Sweet corn or popcorn can be planted the second year after land is treated with atrazine. Follow mixing instructions carefully.
Metolachlor + [Cyanazine + Atrazine] (Dual 8E + Extrazine 90 DF): Application rate is 2 pt + 2.8 lb per acre. Apply as preplant or preemergent by ground spray. Do not use if small grains or other crops are to be
planted the same year or if other vegetable crops or tobacco are to be planted the next year. Sweet corn or popcorn can be planted the second year after land is treated with atrazine. Follow mixing instructions carefully.
Paraquat (Gramoxone Extra): Application rate is 2 to 3 pt per acre. Apply before, during or after planting by band or broadcast, but prior to crop emergence. Use higher rate for heavy weed infestations.
Paraquat (Gramoxone Extra [heavier strength]): Application rate is 12.8 fl oz of 3/4 pt per acre. Apply when corn is at least 10 inches tall by ground spray with nozzles arranged no higher than the lower 3 inches of corn
stalk. Shorter corn plants may be injured. Can be applied with atrazine for improved control of emerged weeds.
Sethoxydim (Poast 1.5E): Application rate is 1 pt per acre. Apply by ground spray to plants that are at least 30 inches tall. Use drop nozzles and do not apply higher than 10 inches on stalks of corn. Read lable. Caution:
Poast can kill corn if used improperly.
Johnsongrass Controls
Butylate 4 (Eradicane 6.7E or Sutan + 6.7E or Genate Plus 6.7E): Application rate is 4 ½ pt per acre. Apply preplant by ground spray when majority of plants have reached the boot-to-head stage and are 18 inches tall.
Butylate 6 (Sutan Plus 6.7E or Genate Plus 6.7E): Application rate is 7 1/3 pt per acre. Apply preplant for rhizome suppression. Incorporate immediately after application. See incorporation instructions on label. For
rhizome suppression, Sutan Plus or Genate Plus should follow several diskings. See label for specific directions. For better overall wed control, it is suggested that a broadleaf herbicide is used.
Glyphosate + EPTC 4 (Roundup + Eradicane Extra): Application rate is 1 to 3 qt and 5 1/3 pt per acre. Apply preplant by ground spray when majority of plants have reached the boot-to-head stage and are 18 inches tall. When using Roundup at 1 qt/A, apply with 0.5% nonionic surfactant before plowing under. Crops to follow this treatment include corn, soybeans, incorporated oats, wheat, barley and sorghum. Continue good cropping practices such as using a good seedling johnsongrass herbicide. A shallow cultivation (no more than half of the incorporation depth of the herbicide) helps control "escaped" seedling johnsongrass plants. Rainfall within 6
hours of applying Roundup may reduce effectiveness of this treatment. Be very careful to prevent drift of this material. Minute quantities of Roundup can cause severe damage to nearby plants. For better overall weed
control use a broadleaf herbicide. Do not apply with aerial application equipment. Do no mix, store or apply Roundup or Roundup spray solutions in galvanized steel or unlined steel (except stainless steel) containers or
spray tanks.
Sethoxydim (Poast 1.5E): Application rate is 1 pt per acre. Apply at johnsongrass seedling stage by ground spray when corn is at least 30 inches tall. Use drop nozzles and do not apply higher than 10 inches on stalks of corn. See label.
Caution: Poast can kill corn if used improperly.
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