Postemergence

2,4-D amine

Rate 0.24 to 0.71 lb ae/a (0.5 to 1.5 pints/a product)

Time Apply after corn is tall enough to use drop nozzles between rows.

Remarks To avoid drift injury, use the same precautions in spraying 2,4-D as for winter cereals. Avoid contact with corn foliage to reduce brittle stalks and whorl distortion that prevents tassel emergence. Mimics natural plant hormones.

Caution Do not apply from tasseling to dough stage of corn. Crop injury is more likely if corn is growing rapidly under high temperature and high soil moisture.

Site of action Group 4: synthetic auxin

Chemical family Phenoxy acetic acid

atrazine + crop oil

Rate Consult labels.

Time Apply postemergence before grass weeds exceed 1.5 inches and broadleaf weeds 4 to 6 inches but before corn is 12 inches tall.

Remarks Use lower water carrier volumes to improve activity. Do not exceed 1 to 1.5 lb ai/a when wheat is expected to follow in the rotation. Consult label for replanting sensitive crops within 12 to 24 months.

Caution A restricted-use herbicide. Also, any product or premix containing more than 4% atrazine is restricted use (Atrazine 4L is 42% atrazine). Do not exceed 2 lb ai/a for any single application. Do not exceed 2.5 lb ai/a per year. Reduce potential soil residue by keeping applications under 2 lb/a, or select other herbicides.

Site of action Group 5: photosystem II inhibitor

Chemical family s-triazine

bentazon (Basagran 5L)

Rate 0.75 to 1 lb ai/a (1.2 to 1.6 pints/a Basagran 5L)

Time Apply to small, annual broadleaf weeds; see label for maximum weed size.

Remarks Add nonionic surfactant/crop oil concentrate/methylated seed oil and urea ammonium nitrate/ammonium sulfate. Apply postemergence to corn when weeds are small and actively growing. Rainfast in 4 hr. Use higher rate with crop oil concentrate applied twice, 7 to 10 days apart, for Canada thistle and yellow nutsedge control. Irrigate before application to ensure vigorous weed growth. Control is poor if day and night temperatures are below 75°F and 55°F, respectively. Use at least 5 gal/a water and at least 40 psi to ensure thorough coverage of weed foliage. Corn leaves may be speckled temporarily, but plants continue growth without further symptoms within 10 days.

Caution Do not apply to corn growing under stress conditions. Do not mix with insecticides. Do not exceed 2 lb ai/a (3,2 pints/a 5L) per season.

Site of action Group 6: photosystem II inhibitor

Chemical family Benzothiadiazole

carfentrazone (Aim EC)

Rate 0.008 to 0.032 lb ai/a (0.5 to 2 fl oz/a Aim EC). Up to 2 fl oz/a for preemergence burndown or postemergence-directed applications.

Time Apply to actively growing broadleaf weeds up to 4 inches tall or 3 inches across. Apply to corn from before planting up to the 14th collar growth stage, and when weeds are small. Use directed applications if corn is larger than the V-8 stage.

Remarks Adjust nozzles to minimize herbicide application directly over row that might concentrate spray in whorl of corn plant. Acts on contact. Fields can be planted to labeled crops at any time and rotated to any other crop 12 months after application (see label). Good spray coverage is essential.

Caution Avoid applying to corn with collars filled with water. Use only a nonionic surfactant on sweet corn. Avoid any chance of spray drift to non-target sites. User assumes all responsibility for crop loss or damage of sweet corn varieties and inbred lines for seed production. Overlapping applications can injure crop. Tank-mixtures of carfentrazone with emulsifiable concentrate (EC) formulations of other herbicides, fungicides, or insecticides, or with crop oil concentrate, methylated seed oil, or silicone-based adjuvants may increase crop injury. Adding nitrogen or ammonium sulfate with nonionic surfactant may increase leaf injury. Do not exceed 0.031 lb ai/a (2 fl oz/a Aim EC) per season.

Site of action Group 14: inhibits protoporphyrinogen oxidase

Chemical family Triazinone

clopyralid (Stinger)

Rate Apply 0.124 to 0.25 lb ae/a (0.33 to 0.66 pint/a of Stinger) uniformly with ground equipment as a broadcast or directed spray in 10 to 20 gal/a total spray volume.

Time Any time after sweet corn emerges until 18 inches tall.

Remarks To control Canada thistle, apply when most thistle plants have emerged and thistles are at least 6 to 8 inches wide or tall, but before bud stage. For best results on Canada thistle, use at least 0.5 pint/a product. Do not cultivate before treatment; wait 2 weeks after treatment before cultivation. Re-treat as necessary but do not exceed 0.66 pint/a product per calendar year. Preharvest interval is 30 days for ears and forage, 60 days for stover. Make one to two broadcast applications per crop per year, not to exceed a total of 0.66 pint/a. Re-treatment interval is 21 days. To control Jerusalem artichoke, common cocklebur, jimsonweed, ragweed (common and giant), annual sowthistle, and sunflower, apply Stinger from weed emergence up to the five-leaf growth stage. Use a higher rate listed for heavy infestations, or when greater residual control is desired.

Caution Preharvest interval is 30 days for ears and forage, 60 days for stover. Make one to two broadcast applications per crop per year, not to exceed a total of 0.66 pint/a. Re-treatment interval is 21 days. Do not graze treated areas or harvest corn for feed within 40 days of treatment. Wheat, barley, canola, Brassica crops (including those grown for seed), garden beets, sugar beets, oats, grasses, field corn, spinach, or turnips may be planted any time after treatment. Asparagus, grain sorghum, mint, onion, and strawberries can be planted 12 months after application. Alfalfa, dry bean, soybeans, and sunflowers can be planted 1 month after application if rain (not including irrigation) is greater than 18 inches, or after 18 months if rainfall is less than 18 inches. Do not plant broadleaf crops grown for seed (excluding Brassica seed crops), carrot, celery, lentils, lettuce, melons, peas, potatoes, safflower, or tomato for 18 months after applying clopyralid.

Site of action Group 4: synthetic auxin

Chemical family Pyridine

fluroxypyr (Starane)

Rate 0.125 lb ae/a (0.66 pint/a Starane)

Time Apply broadcast to actively growing broadleaf weeds before they are 8 inches tall, and up to and including four fully exposed leaf collars (V4 growth stage). After the V5 or V4 stages, apply as a directed spray with drop nozzles.

Remarks Primarily to control volunteer potatoes in sweet corn, but acts on a number of broadleaf weeds.

Caution Not all sweet corn varieties have been screened for tolerance to fluroxypyr, and varieties may differ in their tolerance. Do not allow grazing. Preharvest interval is 47 days for foraging treated field corn, 31 days for sweet corn ears. Do not add a spray adjuvant when applying fluroxypyr alone on sweet corn.

Site of action Group 4: synthetic auxin

Chemical family Pyridine

fluthiacet-methyl (Cadet)

Sweet corn for processing only

Rate 0.004 to 0.006 lb ai/a (0.6 to 0.9 fl oz/a Cadet)

Time Apply to corn from 2-leaf (two leaf collars) to when corn is 48 inches tall or before tasseling, whichever comes first. See label for maximum growth stage and weeds controlled.

Remarks See label for maximum weed size, usually 3 inches or less tall with the exception of velvetleaf (36 in tall). Spray adjuvants are required for optimum weed control. See label for adjuvant recommendations. Thorough coverage is essential for control of susceptible broadleaf weeds. Lower rate can be used if tankmixing with glyphosate for preplant burndown.

Caution Do not exceed 0.009 lb ai/a (1.25 fl oz/a Cadet) per season.

Site of action Group 14: protoporphyrinogen oxidase inhibitor

Chemical family Imine

halosulfuron-methyl (Sandea)

Rate 0.03 to 0.047 lb ai/a (0.66 to 1 oz/a Sandea)

Time Apply postemergence from spike through layby stage.

Remarks Sandea is not recommended for use on "Golden Jubilee." Avoid concentrating into the plant whorl. Controls only susceptible broadleaf weeds and nutsedge. Nightshades are not controlled. Always add a nonionic surfactant if not tank mixed with other herbicides. Apply only with ground equipment. May apply up to two times during growing season.

Caution Not all varieties have been tested for sensitivity to this herbicide. Before using, consider crop rotation plans. Do not replant or rotate to wheat within 2 months.

Site of action Group 2: acetolactate synthase (ALS) inhibitor

Chemical family Sulfonylurea

mesotrione (Callisto)

Rate 0.078 to 0.094 lb ai/a (2.5 to 3 fl oz/a Callisto)

Time Apply postemergence to corn less than 5 inches tall.

Remarks Good control of some broadleaf weeds, with suppression of wild proso millet. Tank mix with atrazine to improve broadleaf control. Does not control common purslane.

Caution Some sweet corn varieties are much more sensitive to mesotrione than others (See https://agsci.oregonstate.edu/oregon-vegetables/sweet-corn-hybrid-tolera...). Rotation interval is 18 months 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. See label for adjuvant restrictions for sweet corn, which recommends nonionic surfactant rather than crop oil concentrate, particularly under lush growing conditions. Do not add UAN or AMS. Do not apply more than 0.24 lb ai/a per year (7.7 fl oz).

Site of action Group 27: inhibits 4-hydroxyphenylpyruvate dioxygenase (4-HPPD)

Chemical family Triketone

mesotrione + fluthiacet methyl (Solstice)

Rate 0.0739 to 0.0931 lb ai/a mesotrione + 0.0042 to 0.0053 lb ai/a fluthiacet methyl (2.5 to 3.15 oz/a Solstice)

Time Recommended stage is spike to V5-V6 and to weeds < 5 inches tall and 3 inches across.

Remarks Apply with a minimum of 10 gal/a water; 15 gal/a is recommended. Add nonionic surfactant at 0.25% v/v. Crop oil concentrate will improve weed control but may increase injury to corn. Use medium droplets and good pressure to penetrate weed canopy and get good coverage from top to bottom of weeds. Avoid XC (Extremely Coarse) type spray nozzles as coverage is not adequate for contact-type herbicides. May be mixed with other labeled postemergence herbicides.

Caution Do not add urea ammonium nitrate or ammonium sulfate when making postemergence applications of Solstice. Do not harvest for forage within 45 days of application. Do not harvest grain within 70 days of application. Do not harvest sweet corn within 40 days of application.

Site of action (mesotrione) Group 27: 4-HPPD inhibitor; (fluthiacet methyl) Group 14: protoporphyrinogen oxidase inhibitor

Chemical family (mesotrione) Triazinone; (fluthiacet methyl) Imine

nicosulfuron (Accent Q)

Rate 0.03 to 0.06 lb ai/a (0.9 to 1.8 oz/a Accent Q).

Time Apply to actively growing weeds, either broadcast before corn that is 12 inches tall or up to and including 5 leaf-collars or with drop nozzles according to label instructions if corn is taller than 12 inches.

Remarks See label for details, application restrictions, and ways to minimize potential crop injury. Controls wild proso millet at 0.9 oz/a if weeds are less than 4 in tall or wide. In recent research, tank-mixes of Outlook and/or Lorsban or other insecticides caused severe injury. Adjuvants improve uptake into leaves. Not all varieties of sweet corn tolerate Accent equally. Sweet corn variety tolerance to both Accent and Callisto herbicides can be found online at (See https://agsci.oregonstate.edu/oregon-vegetables/sweet-corn-hybrid-tolerance-ratings). Accent Q includes the safener isoxadifen.

Caution Avoid repeat applications in the same field, to minimize selection for resistant weed biotypes. Do not apply as a tank-mix with Basagran (bentazon), as serious injury will result. Do not apply when the difference between the daytime high and the nighttime low temperature is expected to be 35°F or greater. Note precautions about types and timings of insecticide applications and environmental conditions that stress corn growth or reduce corn metabolism of nicosulfuron. Crop rotation is 10 months for corn, except the sweet corn varieties "Merit," "Carnival," and "Sweet Success," for which the minimum time interval is 15 months. Do not graze livestock or feed any treated component within 30 days of application. Read and understand product label thoroughly before treating sweet corn.

Site of action Group 2: acetolactate synthase (ALS) inhibitor

Chemical family Sulfonylurea

paraquat (Gramoxone SL, Firestorm)

Rate 0.49 to 1.0 lb ai/a (1.3 to 2.7 pints/a Gramoxone 3.0)

Time Apply postemergence as a directed spray when corn is at least 10 inches tall.

Remarks Use nozzles arranged to spray no higher than the lower 3 inches of corn stalks. Severe damage and/or complete kill can occur if spray contacts corn plant. Use shielded sprayers to reduce spray contact with corn plants. Add a nonionic surfactant or crop oil concentrate according to label specifications, taking care to avoid anionic formulations that react in the tank to form insoluble precipitates.

Caution A restricted-use herbicide. Do not ingest or inhale spray mist. Wear protective face shields, respirators, and clothing.

Site of action Group 22: photosystem I electron diversion.

Chemical family Bipyridilium

pyroxasulfone + fluthiacet methyl (Anthem)

Rate 0.067 to 0.218 lb ai/a (4.0 to 13.0 fl oz/a) depending on soil type, soil organic matter and timing of application.

Time Apply from 1-leaf through V4 stage. See label for soil type, organic matter, and rate information.

Remarks Postemergence applications may be made up to V4 stage. Apply alone or in a tank-mixture to broaden weed spectrum. Where emerged weeds are present at the time of application, use appropriate weed control measures to control emerged weeds. For early preplant applications in reduced-tillage systems, use the higher rate for soil type. Requires rainfall or irrigation to activate.

Caution Do not exceed a total of 16.3 oz/a of Anthem per season. See label for rotational restrictions. Do not harvest field corn for forage for 30 days after application. Do not harvest for grain for 70 days after application. Do not harvest sweet corn forage or ears until 40 days after application. Make only one preplant/preemergence application per season.

Site of action (pyroxasulfone) Group 15: inhibits long chain fatty acid synthesis; (fluthiacet methyl) Group 14: protoporphyrinogen oxidase inhibitor

Chemical family (pyroxasulfone) Chloroacetamide; (fluthiacet methyl) Imine

pyroxasulfone + fluthiacet methyl + atrazine (Anthem ATZ)

Rate 1.126 to 2.253 lb ai/a (32 to 64 oz/a Anthem ATZ )

Time Apply from 1-leaf through V4 stage. See label for soil type, organic matter, and rate information.

Remarks Postemergence applications may be made up to V4 stage. Apply alone or in a tank-mixture to broaden weed spectrum. Where emerged weeds are present at the time of application, use appropriate weed control measures to control emerged weeds. For early preplant applications in reduced-tillage systems, use the higher rate for soil type. Requires rainfall or irrigation to activate.

Caution Restricted-use herbicide. Do not exceed a total of 39 oz/a of Anthem ATZ per season on coarse-textured soils or 70 oz/a on fine-textured soils. See label for rotational restrictions. Preplant surface applications are not recommended on coarse soils where annual rainfall exceeds 40 inches. Do not harvest field corn for forage for 60 days after application. Do not harvest for grain for 70 days after application. Do not harvest sweet corn forage or ears until 45 days after application. Make only one preplant/preemergence application per season.

Site of action (pyroxasulfone) Group 15: inhibits long chain fatty acid synthesis; (fluthiacet methyl) Group 14: protoporphyrinogen oxidase inhibitor; (atrazine) Group 5: photosystem II inhibitor

Chemical family (pyroxasulfone) Chloroacetamide; (fluthiacet methyl) Imine; (atrazine) Triazine

tembotrione (Laudis)

Rate 0.082 lb ai/a (3 fl oz/a Laudis)

Time Apply to actively growing weeds from emergence to the V8 stage of growth, or sweet corn up to the V7 stage of growth.

Remarks One application per season on sweet corn. Does not control purslane. Tankmixing with low rates of atrazine significantly improves control of many weeds including purslane and crabgrass. Consult label for maximum weed size. Use methylated seed oil (MSO) at 1% v/v plus ammonium nitrogen fertilizer (UAN) at 1.5 quarts/a or 1.5 lb/a spray-grade ammonium sulfate (AMS) when tembotrione is used alone, or when a specific adjuvant is not specified on the label. Adding atrazine at 1 pint/a significantly broadens the spectrum of control. Tank-mixes with residual herbicides such as S-metolachlor (Dual Magnum) and dimethenamid-P (Outlook) will improve long-term control but may increase potential of crop injury. Potential injury from these tank-mixes can be minimized by applying after V4 stage of corn growth, by eliminating UAN from the tank-mix, or avoiding application after cool and wet weather.

Caution Not all hybrids of corn have been tested for herbicide tolerance. The variety Captain appears to be more sensitive than other corn varieties to tembotrione. New varieties should be screened for tolerance to tembotrione on small areas of fields. Weed control may be reduced if applied to stressed weeds or weeds covered by dust or heavy dew. Do not graze livestock or harvest for forage within 45 days after application. Note crop rotation restrictions on label.

Site of action Group 27: inhibits 4-hydroxyphenylpyruvate dioxygenase (4-HPPD)

Chemical family Triketone

tolpyralate (Shieldex 400SC)

Rate 0.026 to 0.035 lb ai/a (1 to 1.35 fl oz/a)

Time Apply broadcast postemergence to actively growing weeds up to 5 inches tall and to corn up to 20 inches tall.

Remarks Controls wild proso millet, several other annual grasses, and many annual broadleaf weeds. Does not control purslane. Does not control purslane. Tankmixing with low rates of atrazine significantly improves control of many weeds including purslane and crabgrass. Rate is dependent on weed size. Best results are obtained when applications are made early postemergence when corn and weeds are small. Apply to corn that is less than 12 inches tall for improved coverage and best overall performance. Tankmixing tolpyralate with 0.25 to 1 lb ai/a of atrazine greatly improves control of most species, particularly common purslane. Spray additives are essential for maximum control. Methylated seed oil (MSO) is recommended (0.5 to 1 % v/v) but NIS (0.25 to 0.5% v/v) and COC (1% v/v) also can be used. UAN at 2.5% v/v will enhance performance. Spray-grade ammonium sulfate at 8.5 lb/100 gal of water may be substituted for the UAN. Tolpyralate may be used sequentially or in combination with all soil- or foliar-applied insecticides registered for use in corn. Tank-mixes with residual herbicides such as S-metolachlor (Dual Magnum) and dimethenamid-P (Outlook) will improve long-term control but may injure the crop. Potential injury from these tank-mixes can be minimized by applying after the V4 to V6 stage of corn growth, by eliminating UAN from the tank-mix, or avoiding application after extended periods of cool and wet weather. Rainfast in 1 hour.

Caution Preharvest interval is 35 days. Has not been tested on all sweet corn lines for tolerance. Rotational interval is 9 months for most vegetable crops but 18 months for sugar beets. Do not make more than 2 applications per year and more than 2.7 oz/a/year.

Site of action Group 27: inhibits 4-hydroxyphenylpyruvate dioxygenase (4-HPPD)

Chemical family Triketone

topramezone (Impact, Armezon)

Rate 0.0164 to 0.022 lb ai/a (0.75 to 1 oz/a Impact)

Time Apply postemergence to actively growing weeds 3 to 8 inches tall.

Remarks Controls wild proso millet, several other annual grasses, and many annual broadleaf weeds. Does not control purslane. Tankmixing with low rates of atrazine significantly improves control of many weeds including purslane and crabgrass. A supplemental label for Oregon, Washington, and Idaho allows for up to 1 oz/a in single or sequential applications. Rate is dependent on weed size. Add methylated seed oil or crop oil concentrate at 1 to 1.5% v/v and UAN or ammonium phosphate at 1.2 to 1.5% v/v to the spray solution. Spray-grade ammonium sulfate at 8.5 lb/100 gal of water may be substituted for the nitrogen fertilizers. For best performance, tank mix topramezone with 0.25 to 1 lb ai/a of atrazine. Topramezone may be used sequentially or in combination with all soil- or foliar-applied insecticides registered for use in corn. Tank-mixes with residual herbicides such as S-metolachlor (Dual Magnum) and dimethenamid-P (Outlook) will improve long-term control but may injure the crop. Potential injury from these tank-mixes can be minimized by applying after the V4 to V6 stage of corn growth, by eliminating UAN from the tank-mix, or avoiding application after extended periods of cool and wet weather

Caution Apply only once per growing season. Preharvest interval is 45 days. See label (and supplemental label) for Oregon, Washington, and Idaho rotational crop restrictions. Has not been tested on all sweet corn lines for tolerance.

Site of action Group 27: inhibits 4-hydroxyphenylpyruvatedioxygenase (4-HPPD)

Chemical family Triketone

topramezone + dimethenamid-P (Armezon PRO)

Rate 0.5 to 0.857 lb ai/a (14 to 24 fl oz/a product)

Time Apply postemergence to actively growing weeds 3 to 8 inches tall.

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. Controls many annual broadleaf weeds and several annual grasses. See label for optimum treatment time for weeds of different sizes. Apply to corn from emergence up to 50 days prior to harvest or after corn is 12-inches tall, whichever comes first. Tank mix with atrazine (up to 12-inch-tall corn) where possible to improve weed control speed and spectrum. Refer to label for crop rotation restrictions. Add 0.25-0.5 lb ai/a atrazine for best performance. When tank mixing with atrazine, use COC or NIS (not MSO).

Caution Do not exceed 1.147 lb ai/a (28 fl oz/a product) per growing season. Preharvest interval is 50 days. Crop rotation restrictions for snap beans and sugarbeet are determined by location, whether east or west of the Cascade mountains.

Site of action (topramezone) Group 27: inhibits 4-hydroxyphenylpyruvate dioxygenase (4-HPPD); (dimethenamid-P) Group 15: inhibits very long chain fatty acid synthesis

Chemical family (topramezone) Triketone; (dimethenamid-P) Chloroacetamide