March 2012 Newsletter (vol.5)   >>   Beat the Weeds

Dandylion Weed Picture

Granular Pre-Emergence Herbicide Comparison

Spring is right around the corner and with the mild winter we’ve had, now is the time to apply your pre-emergence herbicides.  Make life easy and beat the weeds.  The following charts will help you decide which granular pre-emergence is the best for your application.

Brand Name
Active ingredients

Bag Size
lbs

Rate per
1,000 sq ft
Rate per acre
Residual Control
Ronstar G
 
Oxadiazon
50
2.25-4 lbs
98 to 174 lbs
3 months
Double O
 
Oxyfluorfen + Oryzalin
50
2.3 lbs
100 lbs
3 months
Freehand 0.75G
 
Dimethenamid-P + Pendimethalin
37.5
2.3 to 4.6 lbs
100 to 200 lbs
2 months
Pendulum 2G
Pendimethalin
40
2.3 to 4.6 lbs
100 to 200 lbs
2 months
Two Ox
Oxyflurofen + Oxadiazon
50
2.3 lbs
100 lbs
3 to 4 months
KL 2G
Benefin + Oryzalin
50
2.5 to 7.0 lbs
100 to 300 lbs
3 to 4 months
Preen Plus
Trifluralin + Isoxaben
40
3 to 6 lbs
133 to 267 lbs
8 months
Team 2G
Benefin + Trifluralin
40
1.75 to 3.5 lbs
75 to 100 lbs
3 months
Treflan 5G
Trifluralin
40
1.8 lbs
80 lbs
3 months
Casoron 4G
Dichlobenil
25
50 to 100 lbs

 

The following charts are pre-emergence herbicides labeled for use in ornamentals. They are categorized by weeds they control best and sites in which they can be used.

 

Best for Broadleaves
Field
Container
Landscape
Ground Covers & Vines
Herbaceous Plants
Ronstar G
X
X
X
X
X

 

Best for Grasses
Field
Container
Landscape
Ground Covers & Vines
Herbaceous Plants
Pendulum
X
X
X
X
X
Treflan
X
X
X
X
X
XL (Surflan + Balan)
X
X
X
X
X

 

Combinations
Field
Container
Landscape
Ground Covers & Vines
Herbaceous Plants
Two Ox
X
X
X
Double O
X
X
X
X
X
Preen Plus
X
X
X
X
X

 

Control Some Perennial Weeds
Field
Container
Landscape
Ground Covers & Vines
Herbaceous Plants
Casoron 4G
X
X


Isoxaben
Mode of action: Appears to disrupt root and hypocotyl development, killing susceptible plants prior to emergence from the soil. Very little absorption through foliage.
Crop uses: Established landscape, field, and container-grown woody and herbaceous ornamentals; ground covers; some bulbs; ornamental grasses; and turf.
Weed control strengths: Pre-emergence control of most broadleaved weeds with some suppression of annual grasses.
Weed control weaknesses: Does not control velvetleaf, mallow, morning glory, cutleaf evening primrose, nutsedge, or annual grasses.
Notes: Apply under mulch. May be applied over the top of many ornamental plants. Do not use on bedding plants. Do not apply to ground covers until they are well rooted. Soil or growing medium must be irrigated and well settled before applying to recently transplanted stock. Do not use on Euonymus alatus, lilacs, hydrangea spp, ajuga, iberis, sedum, euphorbia, and mustards. Should be incorporated with cultivation, rainfall, or irrigation within 21 days of application.

 

Oxyfluorfen
Mode of action: Forms a chemical barrier on the soil surface. As weeds grow through it, they are burned off through contact activity. Light is required for activity.
Crop uses: Conifer seedbeds, transplants, container stock, and selected field-grown deciduous trees.
Weed control strengths: Provides excellent control of most broadleaved weeds and many grasses from seed. One of the few pre-emergence herbicides that can provide very good post emergence control of weeds up to 4 inches tall. Controls mile-a-minute weed.
Weed control weaknesses: Does not provide complete control of emerged grasses or large broadleaved weeds. Does not control horseweed. Annual grasses are the first weeds to begin growing in areas treated with Goal.
Notes: Apply over the top of mulch. Oxyfluorfen needs light to be active. Covering with mulch or incorporating will inactivate it. Anything that breaks the chemical barrier (like cultivation) will reduce its effectiveness. Oxyfluorfen can be applied to conifer seedbeds prior to emergence of the conifers. After emergence, wait a minimum of 5 weeks before applying over the top of the conifers. For post emergence control, add 0.25% nonionic surfactant and apply to weed seedlings less than 4 inches tall. Oxyfluorfen can burn the soft growth of broadleaved ornamentals it directly contacts.

 

Pendimethalin
Mode of action: Inhibits root growth through inhibition of cell division and cell elongation.
Crop uses: Field or container-grown woody ornamentals, landscapes, ground covers, herbaceous perennial and annual flowers, ornamental grasses, and turf.
Weed control strengths: Controls most annual grasses and some broadleaved weeds.
Weed control weaknesses: Does not control many annual broadleaved weeds.
Notes: Apply over or under mulch, preferably under. Stains equipment and anything else it contacts. Should be incorporated by cultivation, rainfall, or irrigation within 14 days of application. Delay application to potted bare root liners 2 to 4 weeks after transplanting. Plants in field liner beds must be well rooted with the soil firmed prior to use. May be applied over the top of many ornamental plants.

 

Oxyfluorfen + oxadiazon
Mode of action: Forms a chemical barrier on the soil surface. As weeds grow through it, they are burned off through contact activity.
Crop uses: Landscape, field, and container-grown woody ornamentals.
Weed control strengths: Pre-emergence control of annual grasses and broadleaved weeds.
Weed control weaknesses: Few.
Notes: Anything that breaks the chemical barrier will reduce its effectiveness. Soil particles splashed onto low foliage by coarse irrigation or heavy rainfall can carry enough herbicide to severely injure low-growing, sensitive plants. Laying down a light mulch prior to the herbicide application will prevent this problem.

 

Oxadiazon
Mode of action: Forms a chemical barrier on the soil surface. As weeds grow through it, they are burned off through contact activity. The sprayable formulation can kill existing weeds if they are thoroughly covered.
Crop uses: Landscape, field, and container-grown woody ornamentals; liners; conifer seedbeds; ground covers; some herbaceous ornamentals; and turf.
Weed control strengths: Pre-emergence control of annual grasses and broadleaved weeds. The 50WP formulation will control some emerged weeds.
Weed control weaknesses: Does not control spurge or chickweed from seed.
Notes: Apply over the top of mulch. Ronstar needs light to be active. Covering with mulch or incorporating will inactivate it. Anything that breaks the chemical barrier will reduce its effectiveness. The WP formulation can cause foliar damage; use as a directed spray only. Soil particles splashed onto low foliage by coarse irrigation or heavy rainfall can carry enough Ronstar to severely injure low-growing, sensitive plants. Laying down a light mulch prior to the herbicide application will prevent this problem.

 

Oxyfluorfen + Oryzalin
Stability on soil: Medium to high. Low leaching potential.
Mode of action: Oxyfluorfen acts as a contact herbicide and requires light for activation; oryzalin inhibits root growth.
Crop uses: Field, landscape, and container-grown ornamentals; some ground covers and flowers.
Weed control strengths: Controls most annual weeds.
Weed control weaknesses: Few.
Notes: Apply over the top of mulch. Do not apply to plants with leaves that channel granules to the leaf base. Do not apply 2 weeks before or after leaf bud break; do not apply within 2 months of using other herbicides. Do not apply more than two applications per season. Soil particles splashed onto low foliage by coarse irrigation or heavy rainfall can carry enough herbicide to severely injure low-growing, sensitive plants. Laying down a light mulch prior to the herbicide application will prevent this problem.

 

Isoxaben + Trifluralin
Stability on soil: Low. No significant losses of isoxaben through photodecomposition or volatilization, but trifluralin can be lost through both. Low leaching potential.
Mode of action: Isoxaben appears to disrupt root and hypocotyl development but this has not been documented; trifluralin inhibits root growth.
Crop uses: Field, landscape, and container-grown ornamentals including ground covers, bulbs, herbaceous perennials, ornamental grasses, and nonbearing fruit trees.
Weed control strengths: Controls most annual broadleaved weeds and grasses.
Weed control weaknesses: Few.
Notes: Apply under mulch. See notes for isoxaben and trifluralin. Applications of 150 lb per acre should not be made less than 60 days apart. Do not apply more than 600 lb per acre in a 12-month period. Do not apply within 3 weeks of enclosing overwintering structures. Many growers have found this to be a suitable product for use on a wide variety of herbaceous perennial plants not on the label. However, the user assumes all risk associated with these applications.

 

Treflan
Mode of action: No significant absorption or translocation. Affects seed germination by inhibiting root growth.
Crop uses: Landscape, field, and container-grown woody ornamentals; liners; herbaceous perennials; ground covers; bulbs; and annual flowers. More annual flowers are on this label than on any other pre-emergence herbicide label.
Weed control strengths: Controls most annual grasses and some broadleaved weeds.
Weed control weaknesses: Does not control many annual broadleaved weeds.
Notes: Apply under mulch. Not recommended for muck soils. For best results, cover with a mulch or irrigate within a few hours of application. Can be applied and mechanically incorporated prior to planting. Use lower rates (maximum 2 pints) if mechanically incorporated and higher rates if incorporated with irrigation.

 

XL
Orzalin + Benfin

Stability on soil: oryzalin, high; benefin, medium (photodecomposition). Low leaching potential.
Mode of action: Inhibits root growth.
Crop uses: Established warm season turfgrass; landscape, field, and container-grown ornamentals, including some annual flowers and bulbs and ground covers.
Weed control strengths: Controls most annual grasses and some broadleaved weeds.
Weed control weaknesses: Does not control many annual broadleaved weeds. Mulch: Apply over or under mulch, preferably under.
Notes: Do not use on cool season turfgrass common in the Northeast.