Weed Management in Pepper1
Peter J. Dittmar and William M. Stall2
Peppers are present in the field in some area of Florida every month of the year. Over this period, variable climatic conditions influence the diversity of weed species present, as well as the severity with which weeds affect peppers. Growers should plan a weed-control program that integrates chemical, mechanical, and cultural methods to fit their weed problems and production practices.
Total-farm weed management is more complex than row-middle weed control because several different sites and possibly also several herbicide-label restrictions are involved. Often weed species in row middles differ from weeds on the rest of the farm, and this difference between weed species in different locations might dictate different approaches to weed management. Sites other than row middles where weeds are likely include roadways, fallow fields, equipment parking areas, well and pump areas, fencerows and associated perimeter areas, and ditches.
Disking is probably the least expensive weed control procedure for fallow fields. Where weed growth is mostly grasses, clean cultivation is not as important as in fields infested with nightshade and other disease hosts, including insects. In the latter situation, weed growth should be kept to a minimum throughout the year. If cover crops are planted, those crops should be plants that do not serve as hosts for pepper diseases and insects. Some perimeter areas are easily disked, but berms and field ditches are not, so some form of chemical weed control may have to be used on those areas.
Bare ground can lead to other serious problems, such as soil erosion and sandblasting of plants. However, where undesirable plants exist, some control should be practiced, if practical, and replacement of undesirable plant species with less troublesome ones, such as bahiagrass, might be worthwhile.
Certainly fencerows and areas around buildings and pumps should be kept weed free, if for no other reason than safety. Herbicides can be applied in these situations, provided care is exercised to keep the herbicide from drifting onto the pepper crop.
Use of rye as a windbreak is a common practice in the spring; however, in some cases, it can have adverse effects. If undesirable insects, such as thrips, build up on the rye, contact and systemic grass herbicides can be applied to kill the rye, eliminating it as a host, while the remaining stubble continues to serve as a windbreak.
The greatest row-middle weed problems confronting the pepper industry today are nightshade and dodder.
Nightshade has developed varying levels of resistance to some postemergence herbicides in different areas of Florida. Best control with postemergence (directed) contact herbicides is obtained when the nightshade is 4–6 in. tall, rapidly growing, and not stressed. Two applications of herbicide in about 50 gal. per acre, using a good surfactant, is usually necessary. With postdirected contact herbicides, several studies have shown that gallonage above 60 gal. per acre actually dilutes the herbicides and, therefore, reduces efficacy. Good leaf coverage can be obtained with a volume of 50 gal. or less per acre.
A good surfactant can do more to improve the wetting capability of a spray than increasing the water volume. Many adjuvants are available commercially. Some adjuvants contain more active ingredient than others, and herbicide labels may specify a minimum active ingredient rate for the adjuvant in the spray mix. Before selecting an adjuvant, refer to the herbicide label to determine the adjuvant specifications.
Dodder is a parasitic plant that emerges in row middles. The dodder plants then infect a weed in the row middle and bridge to the pepper plants. If a pepper is "infected" by dodder, controlling the dodder in the row middle will not control the "infection," and the dodder plant may bridge to other pepper plants in the row. Dodder control then necessitates controlling all weeds in the row middles, as well as controlling young dodder seedlings. Contact herbicides labeled for row middles also control young, emerged dodder. Dual and Dacthal® also control dodder when applied preemergence.
Keep in mind, however, that herbicide performance depends on weather, irrigation, soil type, proper selection for weed species to be controlled, and accurate application and timing. Obtain consistent results by reading the herbicide label and other information about proper application and timing of each herbicide. Use only labeled herbicides and use those herbicides in the proper formulation. Use of an herbicide that is not labeled for use on peppers—even if the herbicide may be labeled for row middles in crops that are closely related to peppers, such as tomatoes and eggplant —may damage peppers. When applying an herbicide for the first time in a new area, use only in a small trial area.
Table 1 contains herbicides that should be applied before planting. Table 2 contains chemical control of weeds after planting. Before applying an herbicide, carefully read and follow the label.
Tables
Pretransplant chemical weed control in peppers
Active ingredient lb. a.i./A |
(Trade name) amount of product/A |
Weeds controlled / remarks |
Bensulide 5–6 |
(Prefar®) 4 E 5–6 qt. |
Annual broadleaf and grass weeds. Incorporate 2–4 in. with mechanical cultivation or irrigation. |
Carfentrazone Up to 0.031 |
(Aim®) 2 EC or 1.9 EW Up to 2 fl. oz. |
Emerged broadleaf weeds. Apply as a preplant burndown for emerged broadleaf weeds. Use a crop oil concentrate (COC) or nonionic surfactant (NIS) at recommended rates. May be tank mixed with other herbicides. |
Diquat 0.5 |
(Reglone®) 2 EC 1 qt. |
Broadleaf and grass weeds. Direct spray to the row middles only. Include an NIS in the spray solution. PHI 30 days. |
Flumioxazin Up to 0.128 |
(Chateau®) 51 WDG Up to 4 oz. |
Annual broadleaf and grass weeds. Apply to row middles of raised plastic-mulched beds that are at least 4 in. higher than the treated row middle and 24 in. bed width. Label is a Third-Party Registration (TPR, Inc.). Use without a signed authorization and waiver of liability is a misuse of the product. Tank mix with a burndown herbicide to control emerged weeds. |
Fomesafen 0.25–0.38 |
(Reflex®) 2 SC 1–1.5 pt. |
Broadleaf weeds and sedges. Label is a 24(C) label. Consult a Bayer representative before applying. Apply to a finished planting bed before placing plastic or over top of the plastic. Consult label for plant-back restrictions for corn and sorghum. PHI 70 days. |
Glyphosate 0.3–1.0 |
(Various formulations) Consult labels |
Emerged broadleaf and grass weeds. Apply as a preplant burndown. Allow 3 days between application and planting. Consult label for individual product directions. |
Halosulfuron 0.024–0.05 |
(Sandea®, Profine™) 75 DF 0.5–1 oz. |
Broadleaf control and yellow/purple nutsedge suppression. Apply to row middles only. Do not exceed 2 oz./A per 12-month period. |
Lactofen 0.25–0.5 |
(Cobra®) 2 EC 16–32 fl. oz. |
Broadleaf weeds. Label is a Third-Party Registration (TPR, Inc.). Use without a signed authorization and waiver of liability is a misuse of the product. Apply to row middles only with shielded or hooded sprayers. Contact with green foliage or fruit can cause excessive injury. Drift of Cobra®-treated soil particles onto plants can cause contact injury. A minimum of 24 fl. oz. is required for residual control. Add a COC or NIS for control of emerged weeds. Limit of one PRE and one POST application per growing season. PHI 30 days. |
S-metolachlor 0.64–0.95 |
(Dual Magnum®) 7.62 EC 0.67–1.0 pt. |
Annual broadleaf and grass weeds. Label is a Third-Party Registration (TPR, Inc.). Use without a signed authorization and waiver of liability is a misuse of the product. Apply to the finished bed immediately before laying the plastic. Do not exceed 1.68 pt. of Dual Magnum®/A per crop cycle. |
Napropamide 1–2 |
(Devrinol®) 2 EC 2–4 qt. (Devrinol®) 50 DF 2–4 lb. |
Annual broadleaf weeds. Apply to bed tops after bedding but before plastic application. Rainfall or overhead irrigation of 1 in. is necessary within 24 hours of application. For row middle treatments, do not apply between bloom and harvest and do not exceed 2 lb. a.i./A per crop cycle. |
Oxyfluorfen 0.25–0.5 |
(Goal®) 2 XL 1–2 pt. (GoalTender®) 4 E 0.5–1 pt. |
Must have a 90-day treatment-planting interval for transplanted pepper. Apply as a preemergence broadcast to preformed beds or banded treatment at 0.25–0.5 lb. a.i./A. Mulch may be applied any time during the 90-day interval. |
Paraquat 0.5–1.0 |
(Gramoxone Inteon®) 2 SL 2.0–4.0 pt. (Firestorm®) 3 SL 1.3–2.7 pt. |
Emerged broadleaf and grass weeds. Apply as a preplant burndown treatment. Use an NIS. |
Pelargonic acid |
(Scythe®) 4.2 EC 3%–10% v/v |
Emerged broadleaf and grass weeds. Apply as a preplant burndown treatment. Product is a contact, nonselective, foliar-applied herbicide with no residual control. May be tank mixed with soil residual compounds. |
Pendimethalin 0.48–0.72 |
(Prowl® H2O) 3.8 1.0–1.5 pt. |
Annual broadleaf and grass weeds. May be applied pretransplant but not under mulch. May be applied at 1.0–1.5 pt./A to row middles. Do not exceed 3.0 pt./A/year. PHI 70 days. |
Pyraflufen 0.0008–0.003 |
(ET® Herbicide) 0.208 EC 0.5–2.0 fl. oz. |
Emerged broadleaf weeds. Apply as a preplant burndown treatment. |
Trifluralin 0.5–0.75 |
(Treflan®, Trifluralin, Trifluralin HF) 4 EC 1–1.5 pt. (Treflan® TR-10) 5–7.5 lb. |
Annual broadleaf and grass weeds. Incorporate 4 in. or less within 8 hours of application. Results in Florida are erratic on soils with low organic matter and clay content. Note label precautions against planting noncrops within 5 months. Do not apply after transplanting. PHI 60 days. |
Posttransplant weed control in pepper
Active ingredient lb. a.i./A |
(Trade name) amount of product/A |
Weeds controlled / remarks |
Carfentrazone Up to 0.31 |
(Aim®) 2 EC or 1.9 EW Up to 2 oz. |
Emerged broadleaf weeds. Apply as a hooded application to row middles only. Use a crop oil concentrate (COC) or nonionic surfactant (NIS) at recommended rates. May be tank mixed with other herbicides. Do not exceed 6.1 fl. oz. per cropping season. PHI 0 days. |
Clethodim 0.09–0.13 0.07–0.13 |
(Select®, Arrow®) 2 EC 6–8 fl. oz. (Select Max®) 1 EC 9–16 fl. oz. |
Perennial and annual grass weeds. In fields with heavy grass pressure or larger grass weeds, use higher rates or repeat applications 14 days apart. Use a COC at 1% v/v in the finished spray volume. NIS with Select Max®. PHI 20 days. |
Diquat 0.5 |
(Reglone®) 2 EC 1 qt. |
Broadleaf and grass weeds. Direct spray to the row middles only. Include an NIS in the spray solution. PHI 30 days. |
Halosulfuron 0.024–0.05 |
(Sandea®, Profine™) 75 DF 0.5–1 oz. |
Small-seeded broadleaf and nutsedge. Apply to row middles only. Include an NIS. Do not exceed 2 oz./A per 12-month period. PHI 30 days. |
Imazosulfuron 0.19–0.3 |
(LeagueTM) 0.5 DF 4–6.4 oz. |
Broadleaf, grass, and nutsedge. Do not apply more than 6.4 oz./A or one application per year. Apply to pepper plants that are well established and at least 10 in. tall. Apply directed to the base of the plants and do not contact fruit. Carryover restrictions for cucurbit crops. Consult label for approved surfactants. PHI 21 days. |
S-metolachlor 0.95 |
(Dual Magnum®) 7.62 EC 1.0 pt. |
Annual broadleaf and grass weeds and nutsedge. Label is a Third-Party Registration (TPR, Inc.). Use without a signed authorization and waiver of liability is a misuse of the product. Direct spray solution to row middles only with minimal contact to plants and plastic. Do not exceed 1.68 pt. of Dual Magnum®/A per crop. PHI 60 days. |
Paraquat 0.5 |
(Gramaxone®) 2 SL 2 pt. (Firestorm®) 3 SL 1.3 pt. |
Emerged broadleaf and grass weeds. Direct spray over emerged weeds 1–6 in. tall in row middles between mulched beds. Use an NIS. Use low pressure and shields to control drift. Do not apply more than three times per season. |
Pelargonic acid |
(Scythe®) 4.2 EC 3%–10% v/v |
Emerged broadleaf and grass weeds. Direct spray to row middles. Product is a contact, nonselective, foliar-applied herbicide with no residual control. May be tank mixed with several soil residual compounds. |
Sethoxydim 0.19–0.28 |
(Poast®) 1.5 EC 1.0–1.5 pt. |
Growing grass weeds. A total of 4.5 pt./A can be applied in one season. Include a COC. Unsatisfactory results may occur if applied to grasses under stress. PHI 20 days. |
Footnotes
This document is HS199, one of a series of the Horticultural Sciences Department, Florida Cooperative Extension Service, Institute of Food and Agricultural Sciences, University of Florida. Original publication date March 1999. Revised December 2012. Visit the EDIS website at http://edis.ifas.ufl.edu.
Peter J. Dittmar, assistant professor, and William M. Stall, emeritus professor, Horticultural Sciences Department, Cooperative Extension Service, Institute of Food and Agricultural Sciences, University of Florida, Gainesville, 32611.
The use of trade names in this publication is solely for the purpose of providing specific information, not a guarantee or warranty of the products named, and does not signify that they are approved to the exclusion of others of suitable composition. All chemicals should be used in accordance with directions on the manufacturer's label. Use pesticides safely. Read and follow directions on the manufacturer's label.
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