Preemergence Weed Control within Containers

mulches

Rate On top of the soil, place 0.5 inches of non-decomposable mulch, such as hazelnut shells, sawdust, coco-fiber disks, geotextile disks, or any number of commercially available plastic disks, to prevent weeds from germinating and establishing in wet-dry cycles.

Time During container filling.

Remarks Filling the container with a porous mulch that dries on the container rim prevents weeds from establishing by wetting and drying cycles. This technique can suppress weeds throughout the life cycle of the crop.

Caution Avoid products, including coarse or rigid materials, that might damage the stem of the crops.

dimethenamid-P (Tower)

Rate 0.98 to 1.5 lb ai/a (21 to 32 fl oz/a) depending on weed control needed

Time Apply only to dry crop foliage, either before weed seeds germinate or after completely removing weeds.

Remarks Requires 0.5 inch of water immediately after application to activate the herbicide. For container plants, delay first application to bare-root liners for 2 weeks. Direct spray away from grafted and budded tissue.

Caution Allow soil or planting mixes to settle firmly around transplants after the transplants have been watered and the soil has been packed, Making sure that there are no cracks in the soil that would allow Tower to contact roots directly. Do not apply to unrooted liners or plugs. Do not apply during bud swell, bud break, or at time of first flush of new growth.

Site of action Group 15: inhibits very-long-chain fatty acid synthesis

Chemical family chloroacetamide

dithiopyr (Dimension)

Rate 0.5 lb ai/a (2 pts/a)

Time Apply to bare ground, or containers before target weeds germinate.

Remarks For best weed control, apply to soil that is free from clods, weeds, and debris such as leaves. Requires activation with 0.5 inch or more of rain or irrigation.

Site of action Group 3: microtubule assembly inhibitor

Chemical family Pyridine

flumioxazin (SureGuard)

Rate 0.25 to 0.38 lb ai/a (8 to 12 oz/a SureGuard)

Time Apply to weed-free containers or containers with small weeds (less than 2 inches tall). Apply to established and dormant conifers before bud break or after they have hardened off (see label for list of approved species).

Remarks Direct sprays to avoid contact with the foliage and green bark of broadleaf plants. SureGuard has some postemergence activity on small weeds. Must be activated with water. Preemergence control is better if applied to weed-free containers.

Caution Do not apply over the top of deciduous or broadleaf evergreen crops.

Site of action Group 14: protoporphyrinogen oxidase inhibitor

Chemical family N-phenylphthalimide

flumioxazin (BroadStar 0.25G)

Rate 0.375 lb ai/a (150 lb/a BroadStar)

Time Apply to weed-free containers.

Caution Foliage of desirable crops must be dry at the time of application. Wet foliage will trap granules on the leaf surface, disperse the herbicide, and burn the foliage.

Site of action Group 14: protoporphyrinogen oxidase inhibitor

Chemical family N-phenylphthalimide

flumioxazin + prodiamine (Fuerte)

Rate 0.875 lb ai/a (100 lb/a, max of 200 lb/a per year)

Time Apply before or after weeds emerge. Kills existing annual weeds if weeds are less than 2 inches.

Remarks Can be used safely on established and dormant conifers. Also, can be applied to established deciduous crops (check the label) with directed sprays as long as contact with foliage and green bark is avoided. Injury to linden (Tilia spp.), which has a thin, green bark when young, has been noted in several Oregon nurseries.

Caution Foliage of desirable crops must be dry at the time of application. Wet foliage will trap granules on the leaf surface and burn foliage.

Site of action (Flumioxazin) Group 14: protoporphyrinogen oxidase inhibitor + (Prodiamine) Group 3: microtubule assembly inhibitor

Chemical family (Flumioxazin) N-phenylphthalimides and (Prodiamine) Pyridine

indaziflam (Marengo G)

Rate 0.024 to 0.048 lb ai/a (100 to 200 lb/a product).

Time Marengo G may be applied as a single or in sequential applications over-the-top to container-grown, deciduous, and evergreen trees and shrubs with an established root system.

Remarks Marengo G contains 0.0224% indaziflam. Ornamentals should be established in the container for at least 1 week to allow the soil to settle and plants should be at least 5 inches tall prior to applying Marengo G. Remove granules from the leaves after application. Examine plants to make sure that granules that may have adhered to foliage have been removed. Tolerant species are listed on the label. Apply evenly to soil surface. To apply Marengo G at a use rate of 200 lb of product per acre, spread 0.34 grams into a 6-inch pot.

Caution Do not apply to pots less than 6 inches wide. Application of Marengo G to deciduous foliage or green bark may result in unacceptable injury. Applications made to wet foliage may cause the product to stick to the foliage and lead to localized injury.

Site of action Group 29: inhibits cellulose biosynthesis

Chemical family Alkylazine

isoxaben (Gallery 75 DF)

Rate 0.495 to 0.99 lb ai/a (0.66 to 1.33 lb/a)

Time Apply to weed-free soil in containers.

Remarks Identify weeds and adjust rates according to charts on label. Chemical stability is adequate when left on soil surface for 21 days.

Caution Do not apply to newly transplanted crops until medium is settled (two to three irrigations).

Site of action Group 21: inhibits cell wall synthesis Site B

Chemical family Benzamide

isoxaben + dithiopyr (Fortress)

Rate 1.125 lb ai/a (150 lb/a).

Time Apply to containers before target weeds germinate.

Remarks The two selective active ingredients provide a broad spectrum of weed control with excellent plant tolerance on ornamentals.

Caution Do not apply to newly transplanted crops until the medium is settled (two to three irrigations). Do not apply within three weeks prior to enclosing greenhouses or poly-type structures.

Site of action (isoxaben) Group 21: inhibits cell wall synthesis Site B; (dithiopyr) Group 3: microtubule assembly inhibitor

Chemical family (isoxaben) benzamide + (dithiopyr) Pyridine

isoxaben + trifluralin (Snapshot 2.5TG)

Rate 2.5 to 5 lb ai/a (100 to 200 lb/a Snapshot), depending on prevalent weed species; consult the label

Time Apply to weed-free soil.

Remarks Soil must be settled with water and free of cracks after transplanting. Activate within 3 days using 0.5 inch of water before weeds begin to emerge. See label for repeat treatments.

Caution Do not apply to unrooted liners or cuttings, bedding plants, or newly planted ground cover.

Site of action (isoxaben) Group 21: inhibits cell wall synthesis Site B; (trifluralin) Group 3: microtubule assembly inhibitor

Chemical family (isoxaben) benzamide; (trifluralin) dinitroaniline

isoxaben + trifluralin + oxyfluorfen (Showcase)

Rate 2.5 to 5 lb ai/a (100 to 200 lb/a)

Time Apply to weed-free soil

Remarks Soil must be settled with water and free from cracks after transplanting. Activate within 3 days using 0.5 inch of water before weeds begin to emerge. See label for repeat treatments.

Caution Do not apply to unrooted liners or cuttings.

Site of action (isoxaben) Group 21: inhibits cell wall synthesis Site B; (trifluralin) Group 3: microtubule assembly inhibitor

Chemical family (isoxaben): benzamide; (trifluralin) dinitroaniline: (oxyfluorfen) diphenylether

napropamide (Devrinol 2G or Devrinol 50DF)

Rate 4 ai/a (8 lb/a Devrinol 50DF)

Time Apply any time to weed-free containers and irrigate immediately with 0.5 inch of water.

Remarks Use higher rates on severe weed infestations or if broadleaf weeds predominate. Inhibits root growth.

Site of action Group 15: inhibits very-long-chain fatty acid synthesis

Chemical family Acetamide

oryzalin (Surflan AS)

Rate 2 to 4 lb ai/a (2 to 4 quarts/a Surflan AS)

Time Apply to established plants only in weed-free containers and irrigate as soon as possible with 0.5 inch of water.

Remarks Establish rooted liners in containers at least 2 weeks before treatment. Inhibits cell division or mitosis, primarily in roots.

Caution Do not apply again within 90 days.

Site of action Group 3: microtubule assembly inhibitor

Chemical family Dinitroaniline

oryzalin + oxyfluorfen (Rout)

Rate 100 lb/a (2% + 1% formulation, respectively)

Time Apply product uniformly, after 0.5 inch of water irrigation for potted liners or 3 weeks after potting bare-root liners.

Remarks Irrigate with 0.5 inch of water immediately after application. Note all precautions on label. Acts as a contact herbicide, and inhibits cell division or mitosis in roots and shoots, respectively.

Caution Do not apply to wet foliage or plants with whorls where the granules may lodge.

Site of action (oryzalin) Group 3: microtubule assembly inhibitor; (oxyfluorfen) Group 14: protoporphyrinogen oxidase inhibitor

Chemical family (oryzalin) dinitroaniline; (oxyfluorfen) diphenylether

oxadiazon (Ronstar G)

Rate 2 to 4 lb ai/a (100 to 200 lb/a Ronstar)

Time Apply uniformly with granular applicator any time to weed-free containers when plants are dry. Irrigate with 0.25 to 0.33 inch water immediately after application.

Remarks Pink family weeds (Caryophyllaceae: chickweed, mouseear chickweed, and pearlwort) are resistant. Controls weed seedlings by contact action during emergence.

Caution Do not use in greenhouses, because injury to plants may result from the deposition of active ingredient on leaf surfaces in the condensate.

Site of action Group 14: protoporphyrinogen oxidase inhibitor

Chemical family Oxadiazole

oxyfluorfen (Goal 2XL)

Conifers and selected deciduous trees only

Rate 0.5 to 1.5 lb ai/a (2 to 6 pints/a Goal 2XL), depending on use; check label.

Time Apply after transplanting to dormant conifer stock. Irrigate with 0.5 to 0.75 inch of water for preemergence control of annual grasses and broadleaf weeds.

Remarks Postemergence applications can control susceptible broadleaf weeds up to 4 inches tall. Acts as a contact herbicide. Use direct sprays to avoid contact with green leaves and bark.

Site of action Group 14: protoporphyrinogen oxidase inhibitor

Chemical family Diphenylether

oxyfluorfen + oxadiazon (Regal O-O Herbicide)

Rate 100 lb/a

Time Apply uniformly before weeds begin to germinate and emerge; follow with 0.5 inch of water irrigation to activate the herbicide.

Remarks Avoid application to wet foliage.

Site of action (both) Group 14: protoporphyrinogen oxidase inhibitor

Chemical family (oxyfluorfen) diphenylether; (oxadiazon) oxadiazole

oxyfluorfen + prodiamine (Biathlon)

Rate Broadcast 2.75 lb ai/a (100 lb/a product); Individual Container Applications: 1 gram/sq ft. See Label. It can be re-applied in 3 months. Do not apply over 200 lb per acre per year.

Time Apply Biathlon prior to weed seed germination. For application in the fall, apply two weeks prior to placing plants in an empty, enclosed greenhouse structure.

Remarks Biathlon is applied as a broadcast application. Biathlon is a combination of herbicides containing two selective active ingredients that provide a broad spectrum of weed control with good plant tolerance on ornamentals. Prior to Biathlon application, irrigate with approximately 0.5 inch of water.

Caution Do not apply to wet foliage.

Site of action (oxyfluorfen) Group 14: protoporphyrinogen oxidase inhibitor; (prodiamine) Group 3: microtubule assembly inhibitor

Chemical family (oxyfluorfen) Diphenylether + (prodiamine) Dinitroanaline

oxyfluorfen + pendimethalin (OH2 Ornamental Herbicide II)

Rate 100 lb/a (2% + 1% formulation, respectively), 6 lb/season at 2 lb ai/a/application maximum.

Time Apply product uniformly using a rotary or drop-type granular spreader either after transplanting potted liners (wait until after two to three irrigations to allow media to settle) or 3 to 4 weeks after planting bare-root liners but before weeds emerge.

Remarks Requires 0.5 to 1 inch of water to activate immediately after application. Acts as contact-type herbicide and inhibits mitosis in roots and shoots, respectively.

Site of action (oxyfluorfen) Group 14: protoporphyrinogen oxidase inhibitor; (pendimethalin) Group 3: microtubule assembly inhibitor

Chemical family (oxyfluorfen) diphenylether; (pendimethalin) dinitroaniline

pendimethalin( Pendulum AquaCap, Pendulum 2G)

Rate 2 to 4 lb ai/a (2.1 to 4.2 quarts/a Pendulum; 75 to 100 lb/a Pendulum 2G)

Time Apply only to dry crop foliage, either before weed seeds germinate or after completely removing weeds.

Remarks Requires 0.5 inch of water immediately after application to activate the herbicide. For container plants, delay first application to bare-root liners for 2 to 4 weeks. Inhibits mitosis in roots and shoots.

Caution Do not apply Pendulum AquaCap or 2EC over the top of plants during bud swell or when new leaves are opening.

Site of action Group 3: microtubule assembly inhibitor

Chemical family Dinitroaniline

pendimethalin + dimethenamid-P (Freehand 1.75G)

Rate 100 to 200 lb/a depending on weed control needed

Time Apply only to dry crop foliage, either before weed seeds germinate or after completely removing weeds.

Remarks Requires 0.5 inch of water immediately after application to activate the herbicide. For container plants, delay first application to bare-root liners for 2 to 4 weeks. Very weak on groundsel, but good control of bluegrass and spotted spurge. Inhibits mitosis in roots and shoots.

Caution Allow soil or planting mixes to settle firmly around transplants, making sure that there are no cracks in the soil that would allow Freehand to contact roots directly.

Site of action (pendimethalin) Group 3: microtubule assembly inhibitor; (dimethenamid-P) Group 15: inhibits very-long-chain fatty acid synthesis

Chemical family (pendimethalin) dinitroaniline; (dimethenamid-P) chloroacetamide

prodiamine (Barricade FL or RegalKade G)

Rate 0.65 to 1.5 lb ai/a (21 to 48 fl oz/a Barricade 4L)

Time Apply to weed-free site.

Remarks Follow with 0.5 inch of water as rain or irrigation.

Caution Do not exceed maximum rate listed on label in a 12-month period.

Site of action Group 3: microtubule assembly inhibitor

Chemical family Dinitroaniline

S-metolachlor (Pennant Magnum)

Rate 1.24 to 2.48 lb ai/a (1.3 to 2.6 pints/a Pennant Magnum), 4.2 lb ai/a/yr or crop cycle

Time Apply any time to weed-free containers for ornamentals transplanted at least 5 days.

Remarks Direct spray toward base of ornamental plant to avoid possible injury. Activate herbicide with brief irrigation. Use lower rates on porous media and reduced weed infestations. Provides approximately 60-day control, less under very wet conditions. Inhibits seedling roots and/or shoots.

Caution Do not exceed 4 lb ai/a per year or per crop cycle (whichever is less), in a given area.

Site of action Group 15: inhibits very-long-chain fatty acid synthesis

Chemical family Chloroacetamide