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How to Manage Pests

UC Pest Management Guidelines

| More pests | More crops | About guidelines |

Yellow nutsedge, Cyperus esculentus.

Carrot

Herbicide Treatment Table

(Reviewed 1/09, updated 1/09)

In this Guideline: More about weeds in carrot:
Herbicide Amount/Acre R.E.I.+ P.H.I.+
(trade name)   (hours) (days)
When choosing a pesticide, consider information relating to environmental impact. Not all registered pesticides are listed. Always read label of product being used.
 
PREPLANT
A. METAM SODIUM 42% product 37.5–75 gal 48 NA
  COMMENTS: Soil should be free of large clods and irrigated about 2 weeks before application of the metam sodium. For flood applications, meter metam into water continuously throughout the entire irrigation. Sprinkler applications are much quicker; after running the sprinklers 5–10 minutes to moisten the soil surface and to be sure the system is working properly, inject the total amount of metam into the pump in about 20 minutes, then shut off the system. In any chemigation system, it is very important to have controls in place to prevent water flowing backward into the uncontaminated water source. Fumigants such as metam sodium are a source of volatile organic compounds (VOCs) but are minimally reactive with other air contaminants that form ozone. Fumigate only as a last resort when other management strategies have not been successful or are not available.
 
B. PARAQUAT* 0.49–1 lb a.i.  
  (Gramoxone Inteon) 1.3–2.7 pt 12 NA
  WSSA MODE OF ACTION GROUP NUMBER1: 22
  COMMENTS: A nonselective foliar herbicide that kills emerged weeds. Can be used before planting or after planting, but before the crop emerges. Any crop plants exposed to the spray will be killed, even germinating seed in the crook stage. No soil residual activity. Use the lower rate on small broadleaf weeds, the higher rate on larger weeds and grasses. Highly toxic if ingested, inhaled, or through dermal contact; wear protective clothing. More active on warm, sunny days.
 
C. GLYPHOSATE
  (Roundup) 1–4 lb a.i. (1–4 qt) 4 NA
  . . . or . . .
  (Touchdown HiTech) 1.88 lb a.i. (48 oz) 12 NA
  WSSA MODE OF ACTION GROUP NUMBER1: 9
  COMMENTS: A nonselective, foliar herbicide applied to premade beds before planting to kill emerged weeds. Allow 3 days after treatment before planting. Use the lower rate for annual grasses and weeds, the higher rate on perennial weeds. Consult the label for specific recommendations on particular weed species. Do not apply to weeds stressed for moisture. For perennial weeds, allow 7 days after application before cultivating.
 
D. TRIFLURALIN 0.5–1 lb a.i. 12 NA
  (Treflan HFP)
  WSSA MODE OF ACTION GROUP NUMBER1: 3
  COMMENTS: Controls annual grasses and broadleaf weeds. Incorporate mechanically into the top 2–3 inches of the final seedbed. The lower rates are recommended on sandy soil; however, crop tolerance is excellent.
 
POSTPLANT
Before the crop emerges
A. TRIFLURALIN 0.5–1 lb a.i. 12 NA
  (Treflan HFP) 1–2 pt    
  WSSA MODE OF ACTION GROUP NUMBER1: 3
  COMMENTS: Apply after sowing to prevent weed germination. Incorporate with irrigation water. See label for plantback restrictions.
 
B. LINURON 0.5–1 lb a.i. 24 14
  (Lorox) DF 1–2 lb    
  WSSA MODE OF ACTION GROUP NUMBER1: 7
  COMMENTS: Apply after planting, incorporate with sprinklers. Will control many broadleaf weeds and annual grasses. A postemergent treatment is also allowed, but must not exceed a total of 3 lb linuron/acre/season.
 
C. PENDIMETHALIN
  (Prowl H2O) 2 pt 24 60
  WSSA MODE OF ACTION GROUP NUMBER1: 3
  COMMENTS: Allowed for use under a supplemental label; make sure carrots are currently labeled. Apply before crop and weeds emerge.
 
After the crop emerges
A. LINURON 0.5–1 lb a.i. 24 14
  (Lorox) 50DF, etc. 1–2 lb    
  WSSA MODE OF ACTION GROUP NUMBER1: 7
  COMMENTS: May be applied twice, first when the crop is 3 inches tall. Good control of emerged broadleaf weeds, small grasses, and suppression of yellow nutsedge. Total per season must not exceed 3 lb /acre (or 1.5 lb a.i./acre).
 
B. FLUAZIFOP-P-BUTYL 0.32–0.96 lb a.i. 12 45
  (Fusilade DX) 16–48 fl oz    
  WSSA MODE OF ACTION GROUP NUMBER1: 1
  COMMENTS: A selective, foliar herbicide for control of grasses. A surfactant (crop oil concentrate or nonionic surfactant) is recommended. Safe to the crop. Not effective on drought-stressed grasses or on certain species (e.g., annual bluegrass, sprangletop). Do not apply more than 48 oz/acre/season.
 
C. SETHOXYDIM 0.09–0.47 lb a.i. 12 30
  (Poast) 0.5–2.5 pt    
  WSSA MODE OF ACTION GROUP NUMBER1: 1
  COMMENTS: A selective, foliar herbicide for control of grasses. A surfactant (crop oil concentrate or nonionic surfactant) is recommended. Safe to the crop. Not effective on drought-stressed grasses or certain species (e.g., annual bluegrass, sprangletop).
 
D. CLETHODIM 0.099-0.121 lb a.i. 24 30
  (Select Max) 13–16 fl oz    
  WSSA MODE OF ACTION GROUP NUMBER1: 1
  COMMENTS: Controls annual bluegrass in the 2- to 3-leaf stage as well as other annual and some perennial grasses. Do not apply through any type of irrigation system. Always apply with a crop oil concentrate. Use higher rate on perennial grasses.
 
+ Restricted entry interval (R.E.I.) is the number of hours (unless otherwise noted) from treatment until the treated area can be safely entered without protective clothing. Preharvest interval (P.H.I.) 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.
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. For more information, see http://www.hracglobal.com.
* Permit required from county agricultural commissioner for purchase or use.

[Precautions]

PUBLICATION

[UC Peer Reviewed]

UC IPM Pest Management Guidelines: Carrot
UC ANR Publication 3438
Weeds
R. F. Smith, UC Cooperative Extension, Monterey County
J. Nunez, UC Cooperative Extension, Kern County
Acknowledgment for contributions to Weeds:
C. E. Bell, UC Cooperative Extension, San Diego County
G. J. Poole, UC Cooperative Extension, Los Angeles County

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