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Horticultural Weed Management - Weed Management in Vegetable Crops - pt. 2: Sweet Corn
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Revised November 24, 2008
CORN, SWEET—Site Preparation
,
Stale Seedbeds
,
and Selective Postemergence Applications
See ‘Site Preparation’, ‘Registered Uses for Glyphosate’, and ‘Registered Uses of Aim Herbicide in Food Crops’ at the beginning of the
Vegetables
section in this handbook.
CORN, SWEET—Preplant Incorporated and Preemergence Surface
• EPTC
+ safener (Eradicane)
not for seed stock
Rate
3.14 to 6.14 lb ai/A
Time
Apply preplant to soil dry enough for thorough mixing and incorporate immediately by disking in two directions or rototilling into top 2 to 3 inches of soil.
Remarks
Avoid planting corn seed more than 2 inches deep. Suppresses growth of yellow nutsedge
and wild proso millet
when applied with Outlook (dimethenamid-P)
. Inhibits shoot growth.
Caution
Consult label regarding other tank-mixes. Crop may be injured if growing under adverse conditions such as pest attacks or extended cold and wet or hot and dry periods.
Site of action
Group 8: lipid synthesis inhibitor but not an ACCase inhibitor
Chemical family
Thiocarbamate
• butylate
+ safener (Sutan +)
not for seed stock
Rate
4 to 6 lb ai/A (4.75 to 7.33 pints/A) depending on target weed species
Time
Preplant incorporated—Apply to soil dry enough for thorough mixing and incorporate immediately by disking in two directions or rototilling into top 2 to 3 inches of soil.
Preemergence surface—In semiarid regions of Idaho and eastern Oregon and Washington, may be applied immediately after planting to dry soil surface (at least 0.5 inch deep) that remains free of dew and incidental moisture. Incorporate with overhead irrigation within 36 hours.
Remarks
Avoid planting corn seed more than 2 inches deep. Suppresses growth of yellow nutsedge
and other perennial grasses. Inhibits shoot growth.
Caution
Consult label regarding other tank-mixes. Crop may be injured if growing under adverse conditions such as extended cold/wet or hot/dry periods or pest attacks.
Site of action
Group 8: lipid synthesis inhibitor but not an ACCase inhibitor
Chemical family
Thiocarbamate
• dimethenamid-P
(Outlook)
Rate
0.56 to 0.98 lb ai/A (12 to 21 fl oz/A)
Time
Apply preplant incorporated, preplant surface, or preemergence surface.
Remarks
Consult label for application rate in relation to soil type. Use lower rates on coarse soils with low organic matter or low cation exchange capacity. Control is best if incorporated into soil by overhead moisture or a light mechanical tillage (1 to 2 inches deep) before weed seedlings emerge. May be tank-mixed with other herbicides to improve weed control. Control of wild proso millet
can be enhanced if Outlook is applied preemergence after preplant-incorporating Eradicane
or Dual Magnum.
Caution
Apply to irrigation systems as described on the label. Delayed emergence or leaf wrapping of sweet corn may occur if conditions are extreme (heavy rain and extended periods of water-saturated soil and/or cool weather) during germination and emergence, particularly for preplant-incorporated applications followed by cool, wet weather. Do not apply on sweet corn grown for seed.
Site of action
Group 15: inhibits very long chain fatty acid synthesis
Chemical family
Chloroacetamide
•
S-
metolachlor
(Dual Magnum or Dual II Magnum with corn safener) or
• metolachlor
(Parallel)
Rate
Consult labels to adjust rates for soil types and organic matter content.
Time
Apply preplant incorporated, preemergence, or early postemergence before weeds germinate or yellow nutsedge
emerges.
Remarks
Activate with shallow incorporation or overhead moisture. Dual II has corn safener.
Caution
Consult label for specific rates, depending on soil texture and especially organic matter, or for restrictions on planting sensitive crops within 4 to 5 mo. Inhibits roots and shoots.
Site of action
Group 15: inhibits very long chain fatty acid synthesis
Chemical family
Chloroacetamide
• alachlor
(Micro-Tech or several premixes with atrazine)
Rate
2 to 3.5 lb ai/A (2 to 3.5 quarts/A) depending on application timing and soil type
Time
Preplant incorporated—apply immediately before planting, and incorporate mechanically in top 1 to 2 inches of soil for furrow-irrigated corn. Preemergence surface—apply after planting and incorporate by cross-harrowing with a spike-tooth harrow; or activate with overhead irrigation.
Remarks
Can apply through a center-pivot irrigation system. See label for specific rates, depending on soil texture, organic matter, and possible use of tank-mixes or other herbicide combinations. Controls atrazine-resistant redroot pigweed
, nightshade, and purslane. Inhibits roots and shoots.
Caution A restricted-use herbicide
due to ground and surface water contamination potential.
Site of action
Group 15: inhibits very long chain fatty acid synthesis
Chemical family
Chloroacetamide
• mesotrione
(Callisto)
Rate
0.188 to 0.24 ai/A (6 to 7.7 fl oz/A)
Time
Apply preemergence surface after planting.
Remarks
Good control of some broadleaves. Tank-mix with atrazine
to improve weed control.
Caution
Some sweet corn varieties are more sensitive than others. Rotational interval is 18 mo for peas, snap beans, cucurbits, beets, and many other crops. Crop yield may be reduced if applied to corn treated with the insecticides Counter or Lorsban.
Site of action
Group 28: inhibits 4-hydroxyphenylpyruvatedioxygenase (4-HPPD)
Chemical family
Triketone
• pendimethalin
(Prowl 3.3EC or Prowl H2O)
Rate
0.74 to 1.98 lb ai/A (1.8 to 4.8 pints/A Prowl 3.3, or 2 to 4 pints/A Prowl H2O) depending on soil texture and organic matter content.
Time
Apply preemergence only; do not preplant-incorporate
. Apply over a uniform seedbed with corn seed planted 1.5 inches deep to ensure selectivity.
Remarks
Note rates listed on label for different soil types and organic-matter contents.
Caution May cause lodging of sweet corn.
Planting deeply may help to reduce lodging. Do not incorporate. Use only shallow cultivation to reduce soil mixing at or near seed. Do not apply to reduced-till or no-till corn.
Site of action
Group 3: microtubule assembly inhibitor
Chemical family
Dinitroaniline
• atrazine
(several brands)
Rate
Consult label for yearly changes.
Time
Apply preplant or preemergence by selecting rates depending on soil type listed on label.
Remarks
Activate with overhead irrigation in 7 days or incorporate mechanically in top 2 inches of soil for rill-irrigated fields east of the Cascades. Control of
barnyardgrass and yellow foxtail is poor
if the soil surface remains dry or if these grasses grow beyond the two-leaf stage. Do not plant crops other than corn during the season of treatment. Other crops can be planted the next year west of the Cascades if treated before June 10 with 2 lb/A or less; east of the Cascades, use other herbicides when planting corn the next year.
Caution
A restricted-use herbicide.
Do not graze treated area or feed treated forage to livestock for 45 days after application. Do not exceed 2.5 lb ai/A per year. After harvest, plow and thoroughly mix the soil to reduce possible injury. Inhibits photosynthesis.
Site of action
Group 5: photosystem II inhibitor
Chemical family
Triazine
• simazine
(Princep 4l, Simazine 4L, and others)
Rate
1.6 to 4 lb ai/A (1.6 to 4 quarts/A, depending on product)
Time
Preemergence, apply before weeds and corn emerge
Remarks
Maximum rate on highly erodible soils is 1.6 quarts/A if less than 30% of the soil is covered with plant residues. Preharvest and pregrazing interval is 45 days. Can be preplant-incorporated.
Caution
A restricted-use herbicide in Washington.
Do not plant crops other than corn for 1 yr. Do not graze treated areas. Do not exceed 2.5 quarts/A per year. After harvest, plow and thoroughly mix the soil to reduce possible injury. Inhibits photosynthesis.
Site of action
Group 5: photosystem II inhibitor
Chemical family
Triazine
• acetochlor
(Harness, Surpass or Cadence)
Rate
0.8 to 3 lb ai/A. Consult appropriate label for rates.
Time
Apply preplant or preemergence.
Remarks
Use lower rates on coarse soils with low organic matter. May be surface-applied or incorporated into top 1 to 2 inches of soil. If rain or 0.25 to 0.75 inch of overhead irrigation does not occur within 7 days of a surface application, shallowly incorporate herbicide with a rotary hoe or similar device. May tank-mix with several other herbicides to broaden activity.
Caution.
Improper incorporation methods or poor soil preparation may reduce weed control. Consult label for crop rotation restrictions.
Site of action
Group 15: inhibits very long chain fatty acid synthesis
Chemical family
Chloroacetamide
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