Weeds Pages
| Common name | Amount per acre | REI‡ | PHI‡ | |
|---|---|---|---|---|
| (Example trade name) | (hours) | (days) | ||
| Not all registered pesticides are listed. The following are listed alphabetically. When choosing a pesticide, consider information relating to environmental impact, resistance management, the pesticide's properties, and application timing. Tank mixes may be necessary to achieve desired control; see Herbicide Susceptibility Table for information on specific weed control. Always read the label of the product being used. | ||||
| ONLY PREPLANT OR FALLOW | ||||
| A. | CARFENTRAZONE | 0.181 lb a.i./season | ||
| (Shark EW) | 11.6 fl oz/season | 12 | 7 | |
| WSSA MODE-OF-ACTION GROUP NUMBER1: 14 | ||||
| COMMENTS: Apply before planting potatoes. | ||||
| B. | TRIFLURALIN | 0.375 lb a.i. | 12 | NA |
| (Treflan HFP) | 0.75 pts | |||
| WSSA MODE-OF-ACTION GROUP NUMBER1: 3 | ||||
| COMMENTS: Apply preplant only tank-mixed with EPTC. Incorporate 2 to 3 inches into the soil, no later than 24 hours after application. Not effective on emerged weeds. | ||||
| PREPLANT AND POSTPLANT | ||||
| Before the weeds emerge | ||||
| A. | DIMETHENAMID-P | 0.5625–0.6562 lb a.i. coarse soils (<3% OM) | ||
| 0.6562–0.8437 lb a.i. coarse soils (>3% OM) | ||||
| 0.6562–0.8437 lb a.i. medium/fine-textured soils (<3% OM) | ||||
| 0.8437–0.9843 lb a.i. medium/fine-textured soils (>3% OM) | ||||
| (Outlook) | 12–14 fl oz coarse soils (<3% OM) | 12 | 40 | |
| 14–18 fl oz coarse soils (>3% OM) | ||||
| 14–18 fl oz medium/fine-textured soils (<3% OM) | ||||
| 18–21 fl oz medium/fine-textured soils (>3% OM) | ||||
| WSSA MODE OF ACTION GROUP NUMBER1: 15 | ||||
| COMMENTS: Apply preemergence following planting or after drag off. Preplant applications can be impregnated on dry bulk fertilizer. Broadcast uniformly followed by rainfall, sprinkler irrigation or shallow mechanical incorporation. On muck and high organic matter soils use the highest rate (0.9843 lb a.i./acre). Do not apply after potato emergence. Not effective on emerged weeds. Can be tank mixed with other preemergence products. | ||||
| B. | EPTC | 3.06–5.25 lb a.i. | ||
| (Eptam 7E) | 3.5–6 pts | 12 | 30 | |
| WSSA MODE OF ACTION GROUP NUMBER1: 8 | ||||
| Apply and immediately incorporate just before planting; or apply after planting potatoes as a direct spray to the soil and incorporate before crop emerges, using rolling cultivators (Lilliston types). Will provide some suppression of hairy nightshade but will not control it on soils exceeding 10% organic matter. May be applied again at layby. Meter into the sprinklers before weeds emerge (about 30 days after the previous application). Do not exceed 14 pt Eptam 7EC per acre per crop. In Lassen, Modoc, Shasta and Siskiyou counties, up to 6 lb a.i./acre per application may be used. Can be tank mixed with other preemergence products. Not effective on emerged weeds. | ||||
| C. | FLUMIOXAZIN | 0.748 oz a.i. | ||
| (Tuscany SC) | 1.5 fl oz. | 12 | NA | |
| WSSA MODE-OF-ACTION GROUP NUMBER1: 14 | ||||
| COMMENTS: Apply after hilling, but before potatoes emerge, otherwise crop injury may occur, because vegetative parts are sensitive. Apply and incorporate when at least 2 inches of soil cover potato sprouts. Ground, chemigation, or aerial application. Do not apply to poorly drained, cool, or wet soil. Can be tank mixed with other preemergence products. | ||||
| D. | METRIBUZIN | 0.250–0.499 lb a.i. | ||
| (TriCor DF) | 0.33–0.66 lb | 12 | 60 | |
| WSSA MODE-OF-ACTION GROUP NUMBER1: 5 | ||||
| COMMENTS: Pre-plant incorporated broadcast spray or impregnated on dry fertilizer. Do not use on Centennial, Shepody or other sensitive varieties. Do not use TriCor DF on potatoes in Kern County, California. Can be tank mixed with other preemergence products. Do not apply after potato emergence. | ||||
| E. | PENDIMETHALIN | 0.7125 lb a.i. coarse soil | ||
| 0.95 lb a.i. medium-textured soil (< 3% OM) | ||||
| 1.425 lb a.i. medium-textured soil (> 3% OM) | ||||
| 1.425 lb a.i. fine-textured soils | ||||
| (Prowl H2O) | 1.5 pts coarse soil & 2 pts medium-textured soil (< 3% OM) 3 pts medium-textured soil (> 3% OM) 3 pts fine-textured soils |
24 | NA | |
| WSSA MODE-OF-ACTION GROUP NUMBER1: 3 | ||||
| COMMENTS: Do not use on muck or peat soils. Works best preemergence on weeds, but somewhat less safe for crop. For annual weeds, apply and soil incorporate into planted beds before potato emergence, or apply preemergence at slightly lower than label rates and sprinkle within 7 days for annual weeds. Do not apply after potatoes are 6 inches tall. Can be tank mixed with other preemergence products. Not effective on emerged weeds. | ||||
| F. | RIMSULFURON | 0.25–0.37 oz a.i. | ||
| (Matrix SG) | 1.0–1.5 oz | 4 | 60 | |
| WSSA MODE-OF-ACTION GROUP NUMBER1: 2 | ||||
| COMMENTS: Apply after hilling or dragoff, before potatoes emerge. Rate can be split into one pre-and one postemergence application. For activation, moisture by rainfall or sprinkler (0.25–0.75 inch) must occur no later than 1 week, but no sooner than 4 hours after application. If weeds are present, then use a nonionic surfactant (NIS) with at least 80% active ingredient at 0.125–0.25% v/v. MSO and/or nitrogen fertilization can also improve control in addition to NIS. Temporary chlorosis may occur if crop is under stress. Check label for plant back restrictions. Can be tank mixed with other preemergence products. If tank mixed with metribuzin do not use surfactant other than NIS. | ||||
| G. | s-METOLACHLOR | 0.955–1.91 lb a.i. | ||
| (Dual II Magnum) | 1.0–2.0 pts | 24 | 60 | |
| WSSA MODE-OF-ACTION GROUP NUMBER1: 15 | ||||
| COMMENTS: Apply preemergence and sprinkle or incorporate shallowly after hilling. Use lower rate on relatively coarse-textured soil or soil low in organic matter. Use the higher rate on fine-textured soils or soils high in organic matter. Do not use on muck or peat soils. Do not harvest within 60 days after the at-planting to drag-off application. Can be tank mixed with other preemergence products. Not effective on emerged weeds. | ||||
| After the weeds emerge | ||||
| A. | CLETHODIM | 0.093–0.25 lb a.i. | ||
| (Intensity) | 6–16 fl oz | 24 | 30 | |
| WSSA MODE-OF-ACTION GROUP NUMBER1: 1 | ||||
| COMMENTS: For grasses. If treatment for broadleaf weeds is planned, do not apply broadleaf application within 1 day of grass treatment, because grass control may be diminished. No fewer than 7 days between cultivation and application. Not effective on weeds which have not emerged. | ||||
| B. | GLYPHOSATE | 0.38–1.1 lb a.i | ||
| (Roundup) | 0.55–1.6 pts | 4 | 14 | |
| WSSA MODE OF ACTION GROUP NUMBER1: 9 | ||||
| COMMENTS: Apply low rates before potato emergence. Avoid contact of spray with the foliage or green stems of potatoes. Do not irrigate for 6 hours after application. For perennial weeds, apply appropriate rate for each weed, usually without a surfactant. Treatments in late summer and fall are best when weeds have been irrigated and are growing well. Not effective on weeds which have not emerged. | ||||
| C. | METRIBUZIN | 0.25 lb–0.499 lb a.i. redroot pigweed/lambsquarters | ||
| 0.499 lb a.i. others | ||||
| (Tricor DF) | 0.33–0.66 lb redroot pigweed/lambsquarters | 12 | 60 | |
| 0.66 lb others | ||||
| WSSA MODE-OF-ACTION GROUP NUMBER1: 5 | ||||
| COMMENTS: Rate can be split between 2 applications, 14 days apart, or split between pre- and postemergence application. Apply before weeds are more than 1 inch tall. Let at least 24 hours pass before other pesticides are used. Do not use on Atlantic, Centennial, Chipbelle, Shepody or other sensitive varieties. Crop injury may occur if postemergence applications are followed by cool, cloudy weather. For use in Modoc and Siskiyou counties only. | ||||
| D. | PARAQUAT* | 0.345–0.69 lb a.i. | ||
| (Gramoxone SL 2.0) | 1–2 pt | 24 | NA | |
| WSSA MODE OF ACTION GROUP NUMBER1: 22 | ||||
| COMMENTS: Delay application as long as possible but apply before potatoes emerge. No more than three applications per year. Apply before potato emergence with a nonionic surfactant. Do not use on muck or peat soils to avoid injury to subsequent crops. For use on emerged annual weeds. | ||||
| E. | RIMSULFURON | 0.25–0.37 oz a.i. | ||
| (Matrix SG) | 1.0–1.5 oz | 4 | 60 | |
| WSSA MODE OF ACTION GROUP NUMBER1: 2 | ||||
| COMMENTS: Apply when weeds are small (< 1 inch high or across). Rate can be split into two postemergence applications or into one pre-and one postemergence spray. The second application can be applied between 14 to 28 days after the first. For activation, supply moisture by rainfall or sprinkler (0.25–0.75 inch) no later than 1 week, but no sooner than 4 hours after application. Use a nonionic surfactant with at least 80% active ingredient at 0.125–0.25% v/v. Temporary chlorosis may occur if crop is under stress. Check label for plant back restrictions. | ||||
| F. | SETHOXYDIM | 0.28 lb a.i. | ||
| (Poast Herbicide) | 1.5 pts | 12 | 30 | |
| WSSA MODE OF ACTION GROUP NUMBER1: 1 | ||||
| COMMENTS: Do not cultivate within 5 days before applying or within 7 days following application. Use a nonphytotoxic oil concentrate in the spray tank. For annual or perennial grasses. | ||||
| HARVEST-BURN DOWN | ||||
| A. | PARAQUAT* | 0.345–0.69 lb a.i. | ||
| (Gramoxone SL 2.0) | 1–2 pt | 24 | NA | |
| WSSA MODE OF ACTION GROUP NUMBER1: 22 | ||||
| COMMENTS: Do not use to desiccate potato vines when potatoes are to be stored or used for seed. Do not exceed 3 pt/acre per season. Use with a nonionic surfactant. | ||||
| HARVEST -VINE DESSICATION | ||||
| A. | DIQUAT | 0.46–0.93 lb a.i. | ||
| (Reglone Desiccant) | 1–2 pt | 24 | 7 | |
| WSSA MODE-OF-ACTION GROUP NUMBER1: 22 | ||||
| B. | GLUFOSINATE | 0.3839 lb a.i. | ||
| (Rely 280) | 21 fl oz | 12 | 9 | |
| WSSA MODE OF ACTION GROUP NUMBER1: 10 | ||||
| ‡ | Restricted entry interval (REI) is the number of hours (unless otherwise noted) from treatment until the treated area can be safely entered without protective clothing. Preharvest interval (PHI) is the number of days from treatment to harvest. In some cases the REI exceeds the PHI. The longer of two intervals is the minimum time that must elapse before harvest. |
| * | Permit required from county agricultural commissioner for purchase or use. |
| NA | Not applicable |
| 1 | Group numbers are assigned by the Weed Science Society of America (WSSA) according to different modes of action. Although weeds may exhibit multiple resistance across many groups, mode of action numbers are useful in planning mixtures or rotations of herbicides with different modes of action. |