Preplant Incorporated and Preemergence

DCPA (Dacthal)

Rate 4.5 lb to 10.5 lb ai/a (3 to 7 qt/a)

Time Apply any time to weed-free soil; must be activated with a minimum of 0.33 to 0.5 inch of irrigation or rainfall water, 3 to 5 days after treatment.

Remarks Applications west of the Cascades usually perform poorly. In other areas, can be applied immediately after planting liners. Inhibits cell division or mitosis in roots and shoots.

Caution Restricted-use herbicide in WA for groundwater protection. Do not use on seedbeds.

Site of action Group 3: microtubule assembly inhibitor

Chemical family Phthalic acid

dichlobenil (Casoron 4G)

Established stock only

Rate 4 to 8 lb ai/a (100 to 200 lb/a granular product)

Time Apply in midwinter immediately before a cold rain, to reduce volatility and to enhance weed suppression.

Remarks Weigh and distribute exact quantities over precisely measured areas to ensure accurate applications. Avoid applying near tree trunks to reduce possible girdling.

Caution Do not apply for 6 months while roots develop on liners, or until 4 weeks after transplanting stock. Oregon results over 9 years suggest that perennial weeds can be suppressed with 4-, 3-, and 2-lb ai/a rates applied during 3 consecutive years. Grazing livestock is prohibited. Inhibits cellulose and cell wall formation.

Site of action Group 20: inhibits cell wall synthesis Site A

Chemical family Nitrile

dithiopyr (Dimension)

Rate 0.5 lb ai/a

Time Apply to bare ground before target weeds germinate.

Remarks For best weed control, apply to a soil that is free from clods, weeds, and debris such as leaves.

Site of action Group 3: microtubule assembly inhibitor

Chemical family Pyridine

EPTC (Eptam 7E)

Rate 5.0 to 6.12 lb ai/a (5.75 to 7 pts/a)

Time Apply 2 weeks before transplanting balled and canned stock (only), or any time after transplanting or growth on established plants begins in spring.

Remarks Use lower rate and incorporate with nursery cultivator or rototillers to 3 inches for annual weeds, and higher rates to 6 inches for perennial weeds. Inhibits shoots of emerging seedlings.

Site of action Group 8: lipid synthesis inhibitor but not an ACCase inhibitor

Chemical family Thiocarbamate

flumioxazin SureGuard (and other trade names)

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

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 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.

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 surface.

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

Remarks Can be used safely on established and dormant conifers. Also, can be applied to established deciduous crops (check 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 leaf surface and burn foliage.

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, tolerant deciduous and evergreen trees and shrubs with an established root system.

Remarks Marengo G contains 0.0224% indaziflam. Marengo G may be applied to the soil surface around established field-grown deciduous and evergreen plants. To avoid root damage, do not apply Marengo G until 2 months after transplanting bare rooted stock, and make sure that soil is well settled around the root area. If transplanting potted plants or balled and burlapped ornamental stock, apply Marengo G after the soil is well settled. Application of Marengo G can be made around dormant or actively growing plants. If applied after dormancy, care should be taken not to contact expanding buds or new leaves. Marengo G should be applied to soil free of weeds, debris, and soil clods for optimum efficacy. Planting into soil treated with Marengo G should be delayed for 3 months to allow for dissipation of the product.

Caution Do not apply to trees that are less than one year old or have been transplanted less than one year, unless completely protected by non-porous wraps, grow tubes, waxed protectors or other forms of protection to young foliage and/or bark. Applications of Marengo G should only be made to ornamentals listed on the label. Do not use Marengo G on ornamentals being grown in a greenhouse, on nursery seedbeds, or on rooted cuttings or young plants in liners. Do not apply Marengo G to plants growing in containers less than 6 inches wide.

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 in late summer to early fall, in early spring, or immediately after cultivation. Apply to debris-free soil surface.

Remarks Identify weeds and adjust rates according to charts on label. Activate with 0.5 inch water or shallow cultivation before weeds emerge. Chemical is stable enough when left on soil surface for 21 days.

Caution Do not apply to newly transplanted crops until media settle.

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 Chemical stability is adequate when left on soil surface for 21 days. For best weed control, apply to soil that is free from clods, weeds, and debris such as leaves.

Caution Do not apply to newly transplanted crops until 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 Snapshot/a)

Time Apply to soil that is free from weeds and debris.

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

Caution Do not apply to unrooted liners or cuttings, bedding plants, or new-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

napropamide (Devrinol 50DF)

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

Time Consult label for crops listed. Apply November to February and irrigate if no rain falls within 2 to 3 days; or apply March through October and irrigate within 24 hours to wet soil 2 to 4 inches deep.

Remarks Shallow mechanical incorporation improves performance. Use higher rates if weed infestations are severe or broadleaf weeds predominate. Inhibits root growth.

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

Chemical family Acetamide

norflurazon (Solicam DF)

Established stock only

Rate 3 lb ai/a

Time Apply in fall or spring to bare soil after nursery crops are established.

Remarks Rain must be adequate before weeds begin to emerge. Read label thoroughly about site, soil, crop rotation, and mixing precautions. Inhibits yellow pigment formation, bleaching green chlorophyll.

Caution Do not apply to cherry, grape, or caneberry nurseries.

Site of action Group 12: bleaching; inhibits carotenoid biosynthesis

Chemical family Pyridazinone

oryzalin (Surflan AS)

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

Time Apply any time to bare soil. Activate within 21 days with 0.5 inch water. Wait at least 90 days before repeating application. Apply only to established plantings.

Remarks Inhibits cell division or mitosis, primarily in roots.

Site of action Group 3: microtubule assembly inhibitor

Chemical family Dinitroaniline

oxadiazon (Ronstar G or Ronstar 50WSP)

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

Time Apply uniformly with granular applicator any time to weed-free soil and when plants are dry.

Remarks Irrigate with 0.25 to 0.33 inch water immediately after applying; do not incorporate mechanically. Weeds in the pink family (Caryophyllaceae: chickweed, mouseear chickweed, pearlwort) are resistant. Controls weed seedlings by contact action during emergence.

Site of action Group 14: protoporphyrinogen oxidase inhibitor

Chemical family Oxadiazole

pendimethalin (Pendulum Aquacap, 2G, EC)

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

Time Apply at planting or before weed seed germinates. Soil should be loose and free from established weeds.

Remarks Water within a few days to activate herbicide before weeds emerge. Inhibits mitosis in roots and shoots.

Site of action Group 3: microtubule assembly inhibitor

Chemical family Dinitroaniline

prodiamine (Barricade 4F)

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

Time Apply to weed-free site.

Remarks Follow with 0.5 inch rain or irrigation, or shallow incorporation.

Caution Do not exceed maximum rate on label in a 12-month period. Do not apply to recently planted red maple (Acer rubrum) liners; this species is not labeled, and severe girdling has been observed in several Oregon nurseries.

Site of action Group 3: microtubule assembly inhibitor

Chemical family Dinitroaniline

pronamide (Kerb)

Established stock only

Rate 1 to 2 lb ai/a

Time Apply in fall before leaves drop or soil freezes. Or, apply from early to midwinter west of the Cascades to soil relatively free of plant residues.

Remarks Requires soil moisture from rain or irrigation to activate; do not incorporate mechanically. Use lower rates for annual grasses and light-texture soils; higher rates for perennial grasses and heavier soils. Control of established grasses is slow. Degraded by microorganisms in warmer weather. Use on nursery stock established at least 1 year and seedlings that are at least 1 year old. Inhibits root growth.

Caution A restricted-use pesticide.

Site of action Group 3: microtubule assembly inhibitor

Chemical family Benzamide

S-metolachlor (Pennant Magnum)

Rate 1.24 to 2.48 lb ai/a (1.3 to 2.6 pints/a Pennant Magnum)

Time Apply any time to weed-free soil as a spray directed to base of ornamentals transplanted at least 10 days.

Remarks Activate herbicide with light irrigation. Use lower rates on sandy soils and reduced weed infestations. Gives about 60 days of control, less under very wet conditions. Suppresses yellow nutsedge when applied preemergence and activated with adequate water.

Caution Do not use on seedbeds or unrooted cuttings. Inhibits seedling roots and/or shoots.

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

Chemical family Chloroacetamide

simazine (Simazine 4L and others)

Established stock only

Rate 2 to 3 lb ai/a

Time Apply at least 1 year after transplanting to weed-free soil and activate with rain or sprinkler irrigation.

Caution Restricted-use herbicide in WA for groundwater protection

Site of action Group 5: photosystem II inhibitor

Chemical family Triazine

trifluralin (4HF or 10G products)

Rate 4 lb ai/a

Time Apply to established nursery crops before weeds germinate. Incorporate with 0.5 inch of irrigation or rain within 3 days of application. Inhibits cell division or mitosis, both in roots and shoots.

Site of action Group 3: microtubule assembly inhibitor

Chemical family Dinitroaniline