UC IPM: Information about Herbicides in Peppermint

UC Pest Management Guidelines

Herbicide

Amount/Acre

P.H.I.+

(trade name)

(days)

PREPLANT

GLYPHOSATE

0.75–5 lb a.i.

(Roundup UltraMax 5S,

1.25–2.5 pt (annual weeds)

Roundup WeatherMax 5.5S,

2–4 qt (perennial weeds)

Touchdown 4S)

COMMENTS: Controls a wide variety of weeds, but is registered for only use before planting , not within 30 days of planting. If may be used after planting only as a spot treatment. Use 2% solutions of product and do not add surfactants when Roundup Ultra is used alone. Add ammonium sulfate (21-0-0-24S fertilizer) according to the label if calcium in the mix water is over 200 ppm (measure with a swimming pool test kit). Repeat applications on difficult to control weeds such as volunteer garlic and field bindweed. Improved field bindweed control has been noted when this material is applied early in the day.

PARAQUAT*

0.49–0.75 lb a.i.

(Gramoxone Max) 3.0

1.3–2 pt

COMMENTS: Excellent on emerged winter annual weeds such as cheatgrass and shepherd's-purse. May be used on both baby and established mint but is poor on volunteer cereals, salsify, and filaree. Combining paraquat at low rates (1/2 label maximum or 0.38 lb a.i.) with low rates of oxyfluorfen (0.13-0.25 lb a.i.) enlarges the spectrum of weeds controlled and enhances weed control. But the combination should not be applied to emerged mint because of the injury potential. Always use a surfactant and apply late in the evening for best results. Weeds that germinate after application will not be controlled.

POSTPLANT

BENTAZON

1–2 lb a.i.

(Basagran) 4EC

2–4 pt

COMMENTS: Controls only broadleaf weeds and is the safest in baby mint. It is relatively expensive because of the higher rates required for effective control. Weak on mayweed chamomile. May be tank mixed with sethoxydim for control of both grass and broadleaf weeds. Use higher rates for larger weeds and weeds such as mayweed chamomile. May be used in newly established mint. Use a crop oil concentrate at the rate of 1 qt/acre with this product. Considered to be a ground water contaminant and requires a use permit within Ground Water Protection Areas.

SETHOXYDIM

0.19–0.48 lb a.i.

(Poast) 1.5S

1–2.5 pt

COMMENTS: Only controls grassy weeds. Applied to emerged grassy weeds where it is absorbed by the leaves. It will not control broadleaf weeds, bluegrass, or fine fescue. It may be used in either baby and/or established mint. The most common use of sethoxydim is to control grasses missed by residual herbicides. If residual herbicides are applied early in fall, their effectiveness is usually gone by late spring and sethoxydim may be used to control summer grasses such as barnyardgrass (watergrass). May be applied in combination with bentazon (Basagran). To improve contact and absorption of both materials use with methylated seed oil or crop oil concentrate.

CLETHODIM

0.10–0.25 lb a.i.

(Prism)

13–34 oz

COMMENTS: Can be used in baby mint and also in established mint for control of grasses. Applied to emerged grassy weeds where it is absorbed by the leaves. It does not have soil activity. It controls both annual and perennial grass weeds, including annual bluegrass. Use the high rate for heavy grass pressure or when grass height exceeds the label recommendation. A crop oil concentrate must be added with this herbicide. Use allowed under a supplemental label.

OXYFLUORFEN

0.13–2 lb a.i.

(Goal) 2XL

0.5–8 pt

(Galigan) 2E

Label rates

COMMENTS: Can only be used on dormant mint from December to March. Will cause some injury to nondormant mint plants, which may reduce yield. Use low rates (0.13-0.25 lb a.i.) on first year mint and higher rates (to 0.5 lb a.i.) on established mint. Apply only one application per season. Particularly effective for cheeseweed and filaree (Erodium spp.). Apply to weeds that are 4 inches or less in size. May be tank mixed with paraquat for improved contact weed control.

FLUMIOXAZIN

2 oz a.i.

(Chateau SW)

4 oz

COMMENTS: Provides burndown of emerged weeds as well as residual control. Effective against small winter annuals. Must be applied to dormant mint otherwise unacceptable injury may occur. May be applied anytime to dormant mint. Apply in a minimum of 15 gallons per acre. May be tank mixed with paraquat and diuron for additional burndown activity. Ammonium sulfate (2-2.5 lb/acre) may be added to improve activity. Use allowed under a supplemental label.

BROMOXYNIL

0.25–0.5 lb a.i.

(Buctril) 2EC

1–2 pt

COMMENTS: Labeled for established mint only. Do not use in spring-planted mint. Apply to dormant mint. Often cause injury to mint, particularly when temperatures are 70°F (or higher) on the day of application or within 5 days of application. Do not add surfactants because increased injury will result. Most effective with least crop damage when applied through automated sprinkler systems. Yields are typically not affected by injury caused at low application rates. Good for control of pigweed, lambsquarters, or sunflowers at young growth stages (less than 6 inches) and when ground application of other herbicides is not possible because of wet soils or dense growth of mint. Do not apply more than 6 pt/acre/season.

DIURON

1.6–2.4 lb a.i.

(Diuron) 4L

1.6–2.4 qt

COMMENTS: Labeled for established mint only, at least 1 year old. Apply only when mint is dormant. Use the low rate on sandy soils. Do not plant susceptible crops within one year if applied rates exceed 1.5 lb a.i./acre. For use only in Del Norte, Humboldt, Lassen, Modoc, Shasta and Siskiyou counties in California under special permission from California Department of Pesticide Regulation. Considered to be a ground water contaminant and requires a use permit within Ground Water Protection Areas.

CLOPYRALID

0.12–0.375 lb a.i.

(Stinger) 3EC

0.33–1 pt

COMMENTS: Apply low rates when weeds are small because injury to mint can occur at high rates. Controls composite weeds such as salsify and legumes such as clover. Do not rotate to susceptible crops (strawberry, alfalfa, onions, potatoes, etc.) within 12 months of application. Do not apply more than one pint/acre/season.

PARAQUAT*

0.49–0.75 lb a.i.

(Gramoxone Max) 3.0

1.3–2 pt

COMMENTS: Apply when crop is dormant and when weeds are less than 6 inches tall. Do not apply more than 0.75 lb a.i./acre/season. More effective weed control can be achieved by mixing with oxyfluorfen at low rates (0.13-0.26 lb a.i. of oxyfluorfen and 0.38 lb a.i. of paraquat). Always add a surfactant.

+	Preharest interval. Do not apply within this many days of harvest.
*	Permit required from county agricultural commissioner for purchase or use.

UC IPM Pest Management Guidelines: Peppermint
UC ANR Publication 3457
Weeds
D. B. Marcum, UC Cooperative Extension, Shasta/Lassen counties
W. T. Lanini, Weed Science/Plant Science, UC Davis
H. L. Carlson, UC Cooperative Extension, Siskiyou Co.

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UC Pest Management Guidelines

Peppermint

Herbicide Treatment Table

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