Annual Grass and Broadleaf Weeds in Established Crop

clomazone (Command 3ME)

Rate 0.5 lb ai/a (21.3 oz/a product)

Time Apply to soil surface before weeds emerge and mint begins new growth.

Remarks Preemergent herbicide. Will not adequately control most grasses. Only one application per season allowed. Off-site movement of spray drift or vapors of clomazone can whiten or yellow some plants. Before applying, check adjacent properties and avoid spraying within 1,200 ft of desirable plants. Overhead moisture after application required to move herbicide into soil. Some, usually temporary, mint discoloration may occur when mint emerges. All use is at the user's and/or grower's risk; users should review the vegetable disclaimer at the end of the label before using. May be tank-mixed with other labeled herbicides to broaden weed control spectrum.

Caution Do not apply more than once per season. Preharvest interval is 84 days. Do not exceed 0.5 lb ai/a (21.3 pints/a Command 3ME). Do not allow particle or vapor drift. Twelve month rotation interval to wheat. Note other crop restriction intervals on label.

Site of action Group 13: inhibits DOXP synthase

Chemical family Isoxazolidinone

diuron (Diuron, Direx, and other trade names)

Rate 0.6 to 2.4 lb ai/a depending on soil organic matter

Time Apply to mint during late-winter dormant period or after flaming in spring before new growth emerges.

Remarks Adjust application rate according to soil organic matter. Treatments applied to growing mint often injure crop. Diuron works best when applied to moist soils and followed by 0.5 to 1 inch of rain or overhead irrigation to move herbicide into the weed root zone before weeds germinate. If weeds are present at time of application, a surfactant at 0.25% v/v or a crop oil concentrate at 1% v/v may enhance control. Weeds larger than 2 inches tall or across at time of treatment may not be controlled. May be tank-mixed with other herbicides, provided mixture is not applied to actively growing mint. Tank-mixes and sequential treatments with other herbicides can increase the risk of crop injury. Use lower rate of diuron unless experience indicates it is safe to use higher rates.

Caution This product is only labeled for use in peppermint. Do not use on sand, loamy sand, gravelly soils, or exposed subsoils, or if soil organic matter is less than 1%. Do not apply to soils that have a high salt content and/or high water table or poor drainage that retards mint root development, resulting in a shallow root system. Do not cultivate after treatment. Do not apply to actively growing mint. Do not apply to mint established less than one growing season in the field or to mint stressed by low fertility, drought, winter injury, insects, disease, or damage from other herbicides or other causes. Do not apply to snow-covered or frozen ground.

Site of action Group 7: photosystem II inhibitor

Chemical family Substituted urea

flumioxazin (Chateau and other trade names)

Rate 0.128 lb ai/a (4 oz/a of products containing 51% ai)

Time Apply to established dormant mint between November 25 and March 1.

Remarks Use for residual preemergence weed control and to aid postemergence burndown of many annual and perennial weeds where established mint is dormant. To control emerged weeds, tank mix with paraquat and apply with a nonionic surfactant. A spray-grade nitrogen source (either ammonium sulfate at 2 to 2.5 lb/a or 28 to 32% nitrogen solution at 1 to 2 quarts/a) may be added to increase burndown of emerged weeds. Controls broadleaf weeds better than grasses.

Caution Applications to nondormant mint may result in unacceptable crop injury. Do not exceed 0.128 lb ai/a (4 oz/a product) in a single application or 0.255 lb ai/a (8 oz/a product) in a single growing season. Do not reapply within 60 days of the first application. Preharvest interval is 80 days. Do not apply to stands established longer than 3 years. Do not apply south of Ladd Canyon in Union or Baker counties in Oregon. Note crop restriction intervals on label. Refer to label for complete list of restrictions. Weather related conditions, including high wind, splashing, heavy rains or cool conditions at or near mint emergence may cause crop injury in fields treated with flumioxazin.

Site of action Group 14: protoporphyrinogen oxidase inhibitor

Chemical family N-phenylphthalimide

napropamide (Devrinol DF-XT, Devrinol 2XT, Devrinol 10G)

See listing in Annual Grass and Broadleaf Weeds in New Plantings and Established Crops

Rate 4 lb ai/a (8 lb/a of 50% products)

Time In furrow-irrigated mint, it is most effective to apply late in the fall to allow winter rain to carry herbicide into soil. In sprinkler-irrigated mint, apply any time before weeds emerge. May be applied to newly planted mint immediately after planting.

Remarks There is some evidence that napropamide breaks down with continued exposure to sun. This photodecomposition can be minimized by rain, sprinkler irrigation, or mechanical incorporation. November through February treatment must be incorporated or irrigated in if no rain falls within 2 weeks of application. Treatments outside of this November through February window must be incorporated or irrigated in within 24 hours if no rain falls. Results are best if mechanically incorporated within 24 hours after application regardless of time of year applied.

Caution Napropamide has injured mint that was not rotovated before herbicide application. Will not control emerged weeds. Do not apply to ground that is frozen or heavily covered with leaves or trash.

Site of action Group 15: inhibits very-long-chain fatty acid synthesis

Chemical family Acetamide

paraquat (Gramoxone Inteon and other trade names)

Rate 0.49 to 0.75 lb ai/a (2 to 3 pints/a Gramoxone Inteon) + nonionic surfactant or crop oil concentrate

Time Apply to dormant mint from November through mid-February.

Remarks Apply in at least 10 gal/a water by ground or 5 gal/a by air. Always add nonionic surfactant or crop oil concentrate as specified on label. Weeds should be succulent, growing, and less than 6 inches tall or across at application. Weeds that germinate after application will not be controlled. The addition of oxyfluorfen improves weed control and this combination is more effective on many weeds than either herbicide alone. Tank mixing with terbacil can improve contact activity and control of Italian ryegrass, prickly lettuce and groundsel. Caution A restricted-use herbicide. Do not apply after mint begins spring growth. Mint foliage present at application may be burned. Use a respirator, chemical resistant gloves, and protective eyewear during application. When handling concentrate a face shield and apron are also required. Paraquat is highly toxic to humans; follow the PPE requirements on the label carefully. Maximum of two applications per year.

Site of action Group 22: photosystem I electron diversion

Chemical family Bipyridilium

pelargonic acid (Scythe)

Rate Apply in a total water volume of 75 to 200 gal per acre. Apply as a 3-5% (v/v) solution on young, small annual weeds and 5-7% (v/v) solution on perennial herbaceous weeds or annual weeds over 6 inches tall. For difficult to control weeds and maximum vegetation control use 7-10% (v/v).

Time Apply while mint is dormant and before mint emerges to control winter annual or early emerged weeds. Don't allow spray to contact emerged mint. Small weeds are easier to control than larger weeds. Warm weather promotes rapid activity on plants.

Remarks Apply as a spot treatment or as a directed and shielded spray avoiding contact with emerged mint. Contact of spray or spray drift with emerged vegetation will result in damage. Repeat applications required to control new weeds emerging from seed or underground vegetative parts. Broadleaf weeds are generally controlled better than grass weeds and repeated use may select for grasses.

Caution Pelargonic acid is a nonselective herbicide and any spray contacting desirable vegetation will likely result in damage. Partially green growth contacted with spray will be killed or stunted.

Site of action Group 26 unknown. Disrupts cell membranes causing leakage from the cells and rapid wilting.

Chemical family Carboxylic acid

pendimethalin (Prowl H2O and other trade names)

Rate 0.71 to 1.9 lb ai/a (1.5 to 4 pints/a of 38.7% formulations). Rate depends on soil texture.

Time Apply to dormant, established peppermint and spearmint before weed seedlings emerge.

Remarks Apply by ground in 10 to 40 gal/a of water, or by air in at least 5 gal/a water. Adequate rain or irrigation after application and before weed seedlings emerge will enhance control.

Caution Do not apply to mint in first year of growth and establishment. Do not apply if mint has broken dormancy. Mint growing under stress conditions is more susceptible to herbicide damage. Preharvest interval is 90 days. Refer to main labels for crop rotation restrictions. Do not exceed 1.9 lb ai/a (4 pints/a) per season. Do not apply through any type of irrigation system.

Site of action Group 3: microtubule assembly inhibitor

Chemical family Dinitroaniline

pyroxasulfone (Zidua)

Rate 0.098 lb ai/a (1.85 oz/a) as one single application per year.

Time Apply to dormant, established peppermint and spearmint before target weeds emerge.

Remarks Residual pre-emergent herbicide. Only apply to dormant mint. Can be tank mixed or applied sequentially to improve control spectrum and/or control emerged weeds. Strong on winter annual grasses and pigweed spp.

Caution Do not apply in the first year of growth and establishment. To ensure crop safety, apply well before crop dormancy is expected to break. Do not apply to soils with <1.0% OM or on coarse soils. Temporary crop injury may be observed when the crop first breaks dormancy. Extreme rainfall or extended periods of soil saturation at the time of dormancy break, may result in crop injury in fields treated with pyroxasulfone.

Site of action Group 15: mitosis inhibitor

Chemical family pyrazole

sulfentrazone (Spartan 4F and other trade names)

Rate 0.14 to 0.375 lb ai/a (4.5 to 12 oz/a) depending on soil type and organic matter. Reduce application rate by 25% for new plantings. Do not apply more than 12 oz/a per year.

Time Apply to dormant mint in spring after any cultivation and before new growth emerges, or postharvest in fall or winter after any cultivation when mint is dormant. Split applications may be used for preemergence sequential control of winter annual and summer annual weeds. May be applied to new mint plantings before weeds emerge and mint begins growth.

Remarks Adjust rate for soil type, soil organic matter content, and soil pH. Will not adequately control most grasses. In new plantings, reduce application rate 25% from the rate for established plantings with the particular soil characteristics. Apply with a registered burndown herbicide to control weeds emerged at application. A surfactant is recommended with these tank-mixes to increase control of emerged weeds. Overhead moisture required after application to activate the herbicide. Foliage that persists during dormancy may be discolored. Foliage on new growth may be discolored temporarily. May be tank mixed with other labeled herbicides to broaden weed control spectrum.

Caution Do not apply to soils classified as sand and with less than 1% organic matter content. Applications to stressed mint may injure crop. Applications to emerged mint will severely injure exposed plant tissue. Do not cultivate after applying. Do not exceed 0.375 lb ai/a in a 12-month period. Do not mix with fertilizers. Note re-cropping restrictions on the label.

Site of action Group 14: protoporphyrinogen oxidase inhibitor

Chemical family Triazinone

terbacil (Sinbar WDG)

Rate 0.8 to 1.6 lb ai/a applied preemergence to mint or 0.8 to 1.6 lb ai/a plus recommended surfactant or nonphytotoxic spray oil applied postemergence to small, actively growing weeds (1 to 2 lb/a Sinbar)

Time West of the Cascades, apply before crop emerges in spring or in fall after last cultivation. East of the Cascades, apply before emergence any time after the first settling rain in fall. Do not apply when ground is frozen. Make postemergence applications before broadleaf weeds are 2 inches tall or across, and grasses are 1 inch tall or across. If not applied preemergence, two postemergence treatments may be made.

Remarks Almost all spring terbacil application failures result from inadequate moisture to activate the chemical during the time when weeds are germinating and growing. If moisture is inadequate to activate the chemical, irrigation must follow fall or winter treatment as soon as soil thaws in spring (or promptly after spring treatment). On soils with good subsurface moisture, best results are by applying 0.75 to 1 inch of overhead moisture before weeds are more than 1 inch high. If subsoil is dry, or if weeds have germinated and their roots penetrate deeply into the soil, 1.5 to 3 inches of irrigation may be required. For furrow-irrigated or rill-irrigated mint, take care to thoroughly wet across the entire bed after applying, or weed control may be poor. Control under those conditions may improve by applying in fall, for activation by winter rain, or by incorporating terbacil into top 1 inch of soil during final bed preparation before crop emerges in spring. This is especially true if spring rain is erratic or inadequate to activate terbacil. For fall application west of Cascades, apply early, before weeds emerge. Results have been poor after weeds, such as groundsel and prickly lettuce, develop a taproot. For postemergence application, apply before broadleaf weeds are 2 inches tall or across and before grasses are 1 inch tall or across. Add 0.5 to 1 pint of surfactant per 25 gal of spray mixture, 1 gal/a of nonphytotoxic superior-type spray oil, or 1 quart/a of surfactant-oil mixture (such as Herbimax or MorAct). Two applications of terbacil (preemergence + postemergence or postemergence + postemergence) may be made within 1 year, but the total applied should not exceed 1.6 lb ai/a in any 1 year. This treatment will not control green foxtail. Terbacil resistant common lambsquarters and redroot pigweed are present in many fields in the PNW.

Caution Do not apply within 60 days of harvest. Unless otherwise directed, do not use on sand, loamy sand, or gravelly soils or on soils with less than 1% organic matter. If used on soils with these conditions, limit use to a small area to determine crop response prior to treating larger areas. Do not exceed 1.6 lb ai/a total per season. Residues can persist after mint plow-out and can injure later crops. Do not replant treated areas to any other crop within 2 years after last terbacil application. Deep plowing (10 to 12 inches) helps reduce injury from carryover. Mint sometimes has been injured when terbacil was applied before, with, or after certain insecticides, especially organophosphates such as Dyfonate. Injury usually has been with applications less than 3 weeks apart and has been especially severe on new stands or on mint emerging from shallow, weak roots, particularly on sandy or gravelly soils. To minimize the possibility of injury, follow the labels of both products carefully. Avoid closely timed applications, especially to weak mint on coarse soils. Mint stressed by double cutting, drought, high salt content of soils, insects, diseases, or other factors may be injured.

Site of action Group 5: photosystem II inhibitor

Chemical family Uracil

trifluralin (Treflan and other trade names)

Rate 0.5 to 0.75 lb ai/a (1 to 1.5 pt/a Treflan) depending on soil type

Time Apply to dormant, established peppermint and spearmint.

Remarks Application rate depends on soil type. Must be soil-incorporated 1 to 2 inches deep with equipment that ensures thorough soil mixing and minimum damage to mint. Granular formulation (Treflan TR-10) can be activated within 3 days with 0.5 inch rainfall or sprinkler irrigation rather than mechanical incorporation. It is also possible to apply via chemigation; see label for specific chemigation application instructions. Trifluralin will not control mustards, prickly lettuce, horseweed (marestail), salsify, mallow, or nightshade.

Caution Take care to avoid exposing untreated soil when ditching for rill irrigation. Do not plant sugar beets, red beets, or spinach for 12 months after applying. Do not plant corn, sorghum (milo), or oats for 14 months after applying.

Site of action Group 3: microtubule assembly inhibitor

Chemical family Dinitroaniline