Landscape Architect Articles

2007 July LSMP Turf Care: Postemergent Herbicides07-03-07 | News

Postemergent Herbicides

Adapted from the University of Florida IFAS Extension, by Jeffrey G. Norcini

Postemergent broadleaf weed control applications are only effective when the targeted weeds are actively growing at the time of spraying. Make sure spring applications are made from mid-April through early June, and fall applications in September and October. Spraying in July and August can cause damage or discoloration to turf, as shown here. Photo: www.turffiles.ncsu.edu.

As a Landscape Superintendent you are no doubt dealing with postemergent herbicides to combat weeds. Applied directly to weeds, these herbicides are most capable when the weeds you are targeting are small and actively growing.

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Some postemergent herbicides can be applied over-the-top of ornamental plants. The following herbicides can be safely used over-the-top of some ornamentals when used according to label directions.

Basagran is an example of a postemergent herbicide that can provide effective yellow nutsedge control. Used for eliminating underground tubers, it can be used in both cool and warm season turfgrass and ornamentals, and along roadsides. Photo: basf.com.

Postemergent herbicides that can be applied over-the-top of tolerant ornamental species:

Trade Name: Acclaim Extra

Active ingredient(s): fenoxaprop-ethyl

Labeled Uses: Container, Field, Landscape

Weeds Controlled: Many annual grasses; temporary suppression of some perennial grasses; will not control broadleaf weeds or sedges (nutgrass).

Comments: Be careful when using this herbicide around ornamental grasses.

Trade Name: Asulox
Active ingredient(s): sodium salt of asulam
Labeled Uses: Container, Field
Weeds Controlled: Many annual grasses, horseweed (marestail)
Comments: Commercial use only. Use only on junipers and podocarpus; check label for specific species. Apply only one time per year; do not use a surfactant.

Trade Name: Basagran, Lescogran
Active ingredient(s): bentazon
Labeled Uses: Container, Field, Landscape
Weeds Controlled: Many broadleaf weeds including coffee senna, beggar-ticks, dayflower, Pennsylvania smartweed, sesbania, shepherdspurse, wild mustard, and wild poinsettia; also yellow nutsedge.
Comments: Over-the-top applications only on English ivy, liriope (Liriope spicata and Liriope muscari), and periwinkle (Vinca minor); may cause slight chlorosis on ‘Evergreen Giant’ liriope (Liriope muscari ‘Evergreen Giant’).

While postemergent herbicides can be very effective, they are only one of the tools you can utilize in a weed control program. Because this turf was not properly cared for after an herbicide application, a new infestation of crabgrass has emerged. Be sure turf is mowed, fertilized and irrigated after a spraying to prevent growth in bare soil left open by the recently killed weeds. Photo: www.turffiles.ncsu.edu.

Trade Name: Envoy

Active ingredient(s): clethodim

Labeled Uses: Container, Field, Landscape, Greenhouse

Weeds Controlled: Many annual and some perennial grasses; will not control broadleaf weeds or sedges (nutgrass).

Comments: Be careful when using this herbicide around ornamental grasses.

Trade Name: Goal 2XL
Active ingredient(s): oxyfluorfen
Labeled Uses: Container, Field
Weeds Controlled: When applied at recommended dosages and
weed stages:* several broadleaf and grassy weeds including barnyard grass, red and white clover, giant foxtail, large crabgrass, henbit, wild mustard, common lambsquarters, prickly lettuce, witchgrass.
Comments: Conifers only (several juniper spp., arborvitae spp., and pine spp. – check the label).

Trade Name: Fusilade II, Ornamec 170
Active ingredient(s): fluazifop-butyl
Labeled Uses: Container, Field, Landscape, Greenhouse
Weeds Controlled: Many annual and some perennial grasses, including torpedograss; will not control broadleaf weeds or sedges (nutgrass).

Trade Name: Vantage
Active ingredient(s): sethoxydim (+ surfactant)
Labeled Uses: Container, Field, Landscape
Weeds Controlled: Many annual and some perennial grasses, will not control broadleaf weeds or sedges (nutgrass).
Comments: Be careful when using this herbicide around ornamental grasses.

The following postemergent herbicides are registered for use around ornamental plants when applied as a directed spray. When using these herbicides be sure that the herbicide does not contact desirable vegetation. Use of a shielded spray nozzle or wick applicator is recommended when applying these type of postemergent herbicides in the vicinity of ornamentals or turf.

The brown patches on this Bermudagrass are caused by a species of the fungus called Rhizoctonia. These annoying patches, along with broadleaf weeds such as dandelion, clover, thistle and bindweed can be controlled by postemergent herbicides. They do not, however prevent weed seeds from germinating and reinfesting a lawn. Photo: www.turffiles.ncsu.edu.

Postemergent herbicides that are applied as directed sprays:

Trade Name: Basagran, Lescogran

Active ingredient(s): bentazon

Labeled Uses: Container, Field, Landscape

Weeds Controlled: Many broadleaf weeds including coffee senna, beggar-ticks, dayflower, Pennsylvania smartweed, sesbania, shepherdspurse, wild mustard, and wild poinsettia; also yellow nutsedge.

Comments: Thorough coverage neccessary

Trade Name: Diquat, Reward
Active ingredient(s): diquat
Labeled Uses: Container, Field, Landscape, Greenhouse
Weeds Controlled: Will kill most young, actively growing annual weeds. Only above-ground growth of biennials and perennials will be affected.
Comments: Thorough coverage necessary; repeat applications may be needed

Trade Name: Finale
Active ingredient(s): glufosinate
Labeled Uses: Container, Field, Landscape, Greenhouse
Weeds Controlled: Many broadleaf weeds and grasses as well as some woody species.
Comments: Thorough coverage necessary; rainfast in four hours.

Trade Name: Roundup
Active ingredient(s): glyphosate
Labeled Uses: Container, Field, Landscape, Greenhouse
Weeds Controlled: Many broadleaf weeds and grasses as well as some woody species.
Comments: Use for eliminating weeds around container beds and in field nurseries.

Trade Name: Scythe
Active ingredient(s): pelargonic acid + related fatty acids
Labeled Uses: Container, Field, Landscape, Greenhouse
Weeds Controlled: Controls both annual broadleaf and grass weeds that are less than six inches in height.
Comments: Thorough coverage necessary; repeat applications may be necessary.