Peppers

Pest Management Guidelines


Herbicide Treatment Table

(Reviewed 12/09, updated 11/12)

In this Guideline: More about weeds in peppers:

Herbicide (trade name) Amount per acre R.E.I.+ P.H.I.+
(trade name)   (hours) (days)

  Calculate impact of pesticide on air quality
The following materials are listed in alphabetical order. When choosing a pesticide, consider information relating to environmental quality. Not all registered pesticides are listed. Always read the label of the product being used.
 
FALLOW BEDS
 
A. OXYFLUORFEN 0.25-0.5 lb a.i.    
  (GoalTender) 0.5-1 pt 24 0
  WSSA MODE-OF-ACTION GROUP NUMBER1: 14
  COMMENTS: Provides both preemergence and postemergence control of broadleaf annuals. Rate depends on the size of weeds; it also affects the treatment-to-planting interval on direct-seeded peppers, which varies from 90 days at the low rate to 120 days at the higher rate. Work the beds with a rolling cultivator or similar tool to a depth of 2.5 inches before planting to avoid crop injury, which can result if beds are not thoroughly worked before planting or if seedling peppers are stressed. Once the beds have been worked, the effectiveness of the material is greatly diminished and will no longer provide weed control. Can be applied 30 days or more before transplanting and 90 (for 0.5 pt/acre ) to 120 (1 pt/acre ) days before direct seeding. Work the beds similar to direct-seeded peppers. This herbicide lasts 4-8 weeks in the soil and has a 10-month plantback restriction for nonlabeled crops.
 
PREFORMED BEDS
 
A. CARFENTRAZONE 0.031 lb a.i.    
  (Shark EW) 2 fl oz 12 0
  WSSA MODE-OF-ACTION GROUP NUMBER1: 14
  COMMENTS: A nonselective, burndown application that can be used before transplanting peppers when weeds are less than 4 inches tall or in rosettes less than 3 inches across.
 
B. GLYPHOSATE 0.55-4.5 lb a.i.    
  (Roundup Powermax) Label rates 4 0
  WSSA MODE-OF-ACTION GROUP NUMBER1: 9
  COMMENTS: A nonselective foliar herbicide that can be used up to 3 days before direct seeding takes place. The rate depends upon the weed species present and to some extent on weed size; control is poor when weeds exceed the maximum size indicated on the label. Cheeseweed and burning nettle require the higher rate, as do perennials. Annual weeds are best controlled when small. Apply in 3-20 gal water. Glyphosate provides good annual weed control and some suppression of perennial weeds. Control of perennials improves with late summer or fall applications during noncrop periods when perennials are actively growing.
 
C. PARAQUAT* 0.5-1 lb. a.i.    
  (Gramoxone Inteon) 2-4 pt 24 0
  WSSA MODE-OF-ACTION GROUP NUMBER1: 22
  COMMENTS: A nonselective foliar herbicide that controls only emerged plants and has no residual activity. Applied as a band treatment over the crop row or as a broadcast treatment before seeding or transplanting the peppers or after seeding but before peppers emerge. Any peppers that have emerged at the time of application will be killed along with the weeds. Controls annual weeds and provides some suppression of perennials. Poor control of cheeseweed. Apply when weeds are succulent and from 1-6 inches high; larger weeds are more difficult to control. Apply in 20-60 gal water/acre (10 gal by air) with a nonionic surfactant added at the rate of 8-32 oz/100 gal. Use the high surfactant rate with cereals and heavy weed infestations. Late afternoon applications increase activity. Do not apply when weather conditions favor drift.
 
D. PELARGONIC ACID
  (Scythe) 3-5% v/v in 75 to 200 gal water/acre 12 0
  WSSA MODE-OF-ACTION GROUP NUMBER1: 27
  COMMENTS: A nonselective, burndown application that can be used before seeding or transplanting peppers. The smaller the weeds, the more effective the control.
 
PREPLANT
 
A. BENSULIDE 4-6 lb a.i.    
  (Prefar 4-E) 4-6 qt 12 0
  WSSA MODE-OF-ACTION GROUP NUMBER1: 8
  COMMENTS: A preplant incorporated herbicide that controls annual grasses, but not wild oats or volunteer cereals, and certain broadleaf weeds such as purslane and pigweed. Apply in 10-50 gal water/acre and incorporate to a depth of 1-3 inches; bensulide can also be applied by chemigation or by surface application followed by sprinkler irrigation for incorporation. This material has a long residual (6 months or more in some soils) and 120-day plantback restriction for nonlabeled crops.
 
B. METAM SODIUM* 50-75 gal/treated acre see label 0
  (various trade names)
  COMMENTS: Soil fumigant. Beds must be free of clods and moist (60-80% field capacity). Weed seeds must be imbibed with water and ready to germinate for best results. Soil temperatures should be between 40° to 90°F at a 3-inch depth. Broadcast rate is 50-75 gal/acre, but typically a 6-inch band is treated using 5-7.5 gal per crop acre (single-row planting of peppers). Applications are made using a spray blade cutting 2-3 inches below the soil surface, depending on soil moisture. Disk hillers follow directly behind the spray blade and form a 3- to 5-inch dirt cap over the treated area. Dirt caps are removed and allowed to air before planting. The label requires a 14-21 day preplant interval between application and planting. Avoid moving untreated soil into the banded area. This treatment is effective against nightshade and many other weeds. Other methods of application include incorporation with a power-driven rotary tiller to a depth of 3 inches and rolled to obtain a good seal; application by 2 fertilizer shanks adapted to treat the soil profile to 12-inch depth and a soil cap to seal; or application with a 3-tiered blade injector to a depth of 10-14 inches and the use of a soil cap to seal. Deep placement is not necessary for weed control, but does control other pests such as nematodes and soilborne diseases. It can be applied as a soil drench and is commonly applied through the drip system on beds with or without plastic mulch.
 
C. NAPROPAMIDE 1-2 lb a.i.    
  (Devrinol 2EC) 2-4 qt 24 0
  (Devrinol 50DF) 2-4 lb 24 0
  WSSA MODE-OF-ACTION GROUP NUMBER1: 15
  COMMENTS: A preplant incorporated herbicide; the rate of application of this material depends on soil type. Incorporate to a depth of 1-3 inches soon after application to prevent loss. Band applications are frequently used to reduce cost. Controls most annual grasses and broadleaves, but not nightshades, mustards, horseweed, or flaxleaf fleabane. It has a long residual and can cause problems on crops such as lettuce, sugarbeet, and cereals planted in rotation.
 
D. PENDIMETHALIN 0.475-1.425 lb a.i.    
  (Prowl H2O) 1-3 pt 24 70
  WSSA MODE-OF-ACTION GROUP NUMBER1: 3
  COMMENTS: Labeled for transplanted peppers only as either a broadcast pretransplant surface application before transplanting or as a post-directed spray targeting the soil at the base of the plants to avoid contacting the foliage. Sufficient rainfall or irrigation is needed to activate the herbicide after a post-directed application. Must be applied before weed emergence. Apply lower rates to coarse-textured soils and higher rates to heavier fine-textured soils.
 
E. TRIFLURALIN 0.5-1 lb a.i.    
  (Treflan 4L) 1- 2 pt 12 0
  (Treflan TR-10) 5-10 lb 12 0
  and others
  WSSA MODE-OF-ACTION GROUP NUMBER1: 3
  COMMENTS: Trifluralin is labeled for transplanted peppers only. Rate depends on soil type. It is volatile and must be immediately incorporated to avoid loss. It provides good season-long control of many annual grasses and broadleaves as well as partial control of seedling field bindweed. Apply in 5-40 gal water/acre and incorporate into the top 2-3 inches of the bed before transplanting. Keep treated soil above the roots.
 
POSTPLANT
 
A. CARFENTRAZONE 0.0238 lb a.i.    
  (Shark EW) 1.6 fl oz 12 0
  WSSA MODE-OF-ACTION GROUP NUMBER1: 14
  COMMENTS: May be applied to the row middles using a hooded sprayer. Take care to keep the spray material off the crop.
 
B. CLETHODIM 0.091-0.12 lb a.i.    
  (Select Max) 12-16 fl oz 24 20
  WSSA MODE-OF-ACTION GROUP NUMBER1: 1
  COMMENTS: A systemic herbicide that controls annual and perennial grasses. For ground applications, apply in 10 to 40 gal of spray solution/acre; add a crop oil concentrate at the rate of 1% v/v in the finished spray volume. Grasses must be at the proper size (see label), well watered, and actively growing for good control. Make repeat applications at a minimum interval of 14 days. Do not apply more than 64 fl oz per season.
 
C. HALOSULFURON 0.37-0.75 oz a.i.    
  (Sandea) 0.5-1 oz 12 30
  WSSA MODE-OF-ACTION GROUP NUMBER1: 2
  COMMENTS: For use on seed and transplant peppers for the control of nutsedge. Apply as a directed spray or with shields to avoid contact with the crop. Injury may result if the spray contacts the foliage. Use of 0.25 to 0.5% v/v of nonionic surfactant is recommended. Use of crop oil concentrate or silicone surfactants is not recommended due to increased risk of injury. Do not apply halosulfuron if a soil application of an organophosphate insecticide has been made. Do not apply a foliar organophosphate insecticide within 21 days before or 7 days after any halosulfuron treatment. Not for use in Imperial and Riverside counties.
 
D. NAPROPAMIDE 1-2 lb a.i.    
  (Devrinol 50DF) 2-4 lb 24 0
  WSSA MODE-OF-ACTION GROUP NUMBER1: 15
  COMMENTS: Apply the recommended amount of napropamide to the soil surface immediately after transplanting. It may be applied over the top of the plants. Use 20-50 gal spray/acre and make sure that the material reaches the zone of weed seed germination. Use overhead sprinkler irrigation to wet the soil to a depth of 2-4 inches.
 
E. PELARGONIC ACID
  (Scythe) 3-5% v/v in 75 to 200 gal water/acre 12 0
  WSSA MODE-OF-ACTION GROUP NUMBER1: 27
  COMMENTS: May be applied to the row middles using a hooded sprayer. Take care to keep the spray material off the crop.
 
F. PENDIMETHALIN 0.475-1.425 lb a.i.    
  (Prowl H2O) 1-3 pt 24 70
  WSSA MODE-OF-ACTION GROUP NUMBER1: 3
  COMMENTS: Labeled for transplanted peppers only. Registered for use as a broadcast pretransplant surface application before transplanting or as a post-directed application to transplanted peppers. It can be applied as a post-directed spray to the soil at the base of the plants, avoiding contact with foliage. Following post-directed application, sufficient rainfall or irrigation is needed to activate the herbicide. Must be applied before weed emergence. Apply lower rates to coarse-textured soils and higher rates to heavier fine-textured soils.
 
G. SETHOXYDIM 0.28 lb a.i.    
  (Poast) 1.5 pt 12 20
  WSSA MODE-OF-ACTION GROUP NUMBER1: 1
  COMMENTS: A systemic herbicide that controls most annual and perennial grasses. Apply in 10-20 gal water; add a crop oil concentrate at the rate of 1 qt/acre. Grasses must be at the proper size, well watered, and actively growing for good control. This treatment can be repeated up to 3 times per season with a preharvest interval of 20 days. Read label for restrictions regarding tank mixes.
 
* Permit required from county agricultural commissioner for purchase or use.
+ 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.

[Precautions]

PUBLICATION

[UC Peer Reviewed]

UC IPM Pest Management Guidelines: Peppers
UC ANR Publication 3460

Weeds
R. F. Smith, UC Cooperative Extension, Monterey County
O. Daugovish, UC Cooperative Extension, Ventura County
Acknowledgment for contributions to Weeds:
C. E. Bell, UC Cooperative Extension, Imperial County
W. T. Lanini, Weed Science/Plant Sciences, UC Davis

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