Fortress Ornamental Herbicide

Fortress Ornamental Herbicide

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Product Overview

Fortress Ornamental Herbicide is a specially formulated granular formula that provides pre-emergent control of grassy and broadleaf weeds in field grown ornamentals and nursery containers. It contains a unique combination of two selective active ingredients Isoxaben and Dithiopyr which offers excellent weed control and superior plant tolerance on ornamentals. It works by building a barrier in the soil through inhibition of cell division and interference of cell wall formation in roots and shoots of growing weed seedlings. It features a low odor and dust-free formulation for easier application and more desirable result. Effective against a wide range of unwanted weeds including aster, bittercress, carpetweed, chickweed, dandelion, henbit, knotweed, oxalis, buttercup, parsley-piert, pennywort, pigweed, plantain, purslane, spurge, barnyardgrass, bluegrass, crabgrass, dallisgrass, foxtail, kikuyugrass, and more. Available in 50 lb. bag.

Features and Specs

Active Ingredient Isoxaben - 0.50% Dithiopyr - 0.25%
Target pests Aster, bittercress, hairy brassbuttons, carpetweed, chickweed, dandelion, henbit, knotweed, oxalis, buttercup, parsley-piert, pennywort, pigweed, plantain, purslane, spurge, barnyardgrass, bluegrass, crabgrass, dallisgrass, foxtail, kikuyugrass
For use in Field and container ornamentals.
Application Apply Fortress herbicide at the rate of 150 lbs. per acre.
Pet safe Yes, if used as directed on label.
Formulation Granular.
Special Features Low-odor and dust-free granule.
Shipping Weight 50.00 lbs
Manufacturer OHP Inc. (Mfg. Number: 477)
UPC 896531002619
EPA Registration 59807-19




Aster (heath), bittercress, bittercress (little), bittercress (hairy), brassbuttons (southern), carpetweed, carrot (wild), chamber-bitter, chickweed (mouseear), dandelion, eclipta, galinsoga (hairy), geranium (Carolina), henbit, knotweed (prostrate), ladysthumb, lespedeza (common), lettuce (prickly), mallow (common), marestail, mayweed (chamomile), medic ( black), morningglory (ivyleaf), mustard, oxalis (buttercup), parsley-piert, pennywort, pigweed (redroot), Pineappleweed, plantain (bracted), plantain (broadleaf), plantain (buckhorn), pokeweed (common), purslane (common), rocket (London), rockpurslane (redmaids), sida (prickly), shepherdspurse, sorrell (red), speedwell (corn), speedwell (thymeleaf), spurge (garden), spurge (hyssop), spurge (prostrate), spurge (spotted), sweetclover (yellow), tansymustard (green), woodsorrel (creeping), woodsorrel (yellow)


Barley, barnyardgrass, bluegrass (annual), brome, crabgrass (large), crabgrass (smooth), crabgrass (Southern), crowfootgrass, dallisgrass (seedling), goosegrass, foxtail (green), foxtail (yellow), kikuyugrass, oats (wild), ryegrass (annual & perennial), sandbur, smutgrass


Abelia, Acacia, Agapanthus, Ash, Aster, Balsam fir, Barberry, Birch, Bougainvillea, Broom, Buxus, Camellia, Chrysanthemum, Crape myrtle, Coreopsis, Cotoneasters, Dogwoods, English ivy, Eunoymus, Ficus, Flowering dogwood, Gardenia, Heather, Hosta, Hollies, Ice plant, Japanese maple, Junipers, Leucothoe, Liriope, Magnolias, Mandevilla, Miscanthus, Mondo grass, Oaks, Osteospermum, Palms, Pennisetum, Pieris, Pines, Pittosporum, Plumbago, Privets, Redbud, Redwood, Rhododendron, Rudbeckia, Sago palm, Serviceberry, Spruce, Smoke tree, Yarrow



Restrictions for Containerized and Field Ornamentals

  • Do not apply to moist or wet foliage of ornamentals.
  • Do not apply while plants are producing a new flush of spring growth. Tender, newly forming leaves are especially sensitive and may be injured by the herbicide.
  • Do not apply when extreme cold stress (35 degrees Fahrenheit or lower) is expected.
  • Do not apply product in enclosed greenhouse, polyhouse or poly-enclosed shadehouse structures containing plants as ornamental injury may result.
  • Do not apply within three weeks prior to enclosing greenhouses or poly-type structures.
  • Do not apply to plant types whose leaves channel the herbicide granules in the leaf base or crown area.
  • Do not apply to vegetable or edible fruit bearing crops.
  • Do not use on fruit trees that will bear fruit within one year of application. Non-bearing fruit trees are defined as trees including
  • Citrus (oranges, grapefruit, etc.), pome fruits (apples, pears, etc.) and stone fruits (cherries, peaches, etc.) which will not bear fruit for at least one year following application of Fortress.
  • Do not apply to bedding plants or flowering crops except as described in the cut flower and foliage ornamental section.
  • Do not mechanically incorporate Fortress into soil or potting media.
  • Do not graze or feed forage from treated fields to livestock.
  • Do not disturb the soil surface following application, as the herbicide barrier will be broken, resulting in less than optimum control.
  • Do not apply to unrooted liners or cuttings that have been planted in pots for the first time.
  • Do not apply to bare roots of ornamental plants as injury may result.
  • Do not apply to pots less than 4 inches wide.
  • Do not apply more than 150 pounds of this product (0.375 pound dithiopyr and 0.75 pound isoxaben) per acre per application.
  • Do not apply more than 300 pounds of this product (0.75 pound dithiopyr and 1.5 pounds isoxaben) per acre per year.
  • Do not reapply at less than 3-month intervals and no more than 2 applications per crop per year.


To provide maximum preemergence weed control activity, certain cultural practices should be followed. Before application, the bed or soil surface should be smooth and free of crop and weed trash (decaying leaves, clippings, dead weeds, etc.). Leaves and trash may be removed by blowing the area to be treated or by thoroughly mixing the trash into the soil through cultivation prior to herbicide application.

Apply Fortress when, at least 1/2 inch of irrigation or rainfall is forecasted to occur within 24 hr after application. The best results from Fortress are from applications to established beds or soil surfaces that are left undisturbed during the time period for which weed control is desired. Cultural practices that result in redistribution or disturbance of the soil surface after treatment will decrease the herbicidal effectiveness of Fortress. Cutting water furrows or cultivations that mix untreated soil into treated areas will also reduce the effectiveness of the treatment.


  • Apply to dry foliage only.
  • Water in immediately to wash the particles off the plant foliage.
  • Apply 3.4 lbs. Fortress per 1,000 sq. ft.
  • Repeat application at 3-month intervals.

Before each application, remove any existing weeds. Apply product with a properly calibrated spreader that will assure accurate, even particle distribution. Apply to dry foliage only. To test for moisture, rub hands over plant foliage. Immediately after the application, water in with 1/2 inch of water to wash the particles off the plant foliage and to activate the herbicide. For season-long weed control, repeat applications are required at approximately 3-month intervals during the growing season, but do not apply more than 300 pounds Fortress per acre per year.

Fortress may be applied to recently transplanted and established ornamentals. Irrigation or rainfall must occur soon after application to wash residues off plant foliage and activate the herbicide. Fortress may be applied at any time to established plants. Delay application to allow soil or media to settle around new transplants. Apply Fortress after cuttings form roots and become established. Apply before budding/grafting or after buds/grafts have taken to avoid any inhibition of the tissue union. For optimum control, Fortress should be activated by at least 1/2 inch of rainfall or irrigation prior to weed seed germination and within 3 days following application.


When applied as directed under the conditions described on this label, ornamentals listed under the LIST OF PLANTS TOLERANT TO FORTRESS section have shown tolerance in field trials. However, this product has not been tested on all cultivars of each species or under all possible growing conditions. Under your growing conditions, a limited number of plants should be treated for tolerance evaluations, prior to initiating large-scale applications. Follow directions given below to determine plant tolerance under your growing conditions prior to large scale use.

Users who wish to use Fortress on ornamental plant species not listed on this label may determine the suitability for use by treating a small number of such plants at a directed rate. Prior to treatment of large areas, the treated plants should be observed for any signs of herbicidal injury for 30 to 60 days of normal growing conditions to determine if the treatment is safe to the target plant species. To the extent consistent with applicable law, the user assumes responsibility for any plant damage or other liability resulting from use of Fortress on plant species not listed on this label.

Do Not Use This Product For Weed Control In The Following Ornamental Plant Species:

Bugleweed or ajuga, mustard, dwarf burning bush, spurge, hydrangea, candytuft, Prince of Wales juniper, cajeput tree, Carolina rhododendron, roseum elegans rhododendron


Apply Fortress prior to weed seed germination in the early spring or fall or following a complete weed removal. Repeat application at a 3 month interval (maximum residual) during the growing season. For application in the fall, apply 3 weeks prior to placing plants in an empty, enclosed greenhouse or hoop house structure.

Apply Fortress at 150 pounds per acre per application. A maximum of two applications may be made per year. Do not reapply at less than 3 month intervals for container grown ornamentals. Do not apply Fortress to newly transplanted ornamentals, nursery stock, groundcovers, or ornamental bulbs until potting soil or potting media has settled around the roots. Use of hand packing, irrigation or rainfall will aid in the settling of media. Failure of soil settling or cracks in the soil media will risk plant injury.

Where runoff water is recycled, care must be taken to locate pump intake line opening(s) close to the collection pond surface to avoid disturbing and recirculating clay fractions/organic matter accumulation near the pond bottom. This debris/settlement may contain amounts of previously applied pesticides tied-up on clay/organic matter fractions and may lead to plant injury.

Potted Liners: Start with clean liners; after planting and before Fortress application, irrigate with water to firm potting media around root systems. Allow foliage to dry. Broadcast Fortress evenly over growing area of containers. Water again after application with approximately 1/2 inch of water.

Bare-root Liners: Start with clean liners; broadcast Fortress evenly over growing area of containers 3 weeks after potting. Water after application with approximately 1/2 inch of water.


Apply Fortress at 150 pounds per acre per application. Apply immediately after planting or in the spring prior to weed seed germination or weed removal. A maximum of two applications may be made per year. Do not reapply at less than 3-month intervals for field grown ornamentals. Fortress is not recommended for use on transplanted bare root stock if irrigation is not available.


Unless excluded under specific crops below, follow all use directions listed on the label. Apply Fortress prior to weed seed germination and or after complete removal of weeds. After planting and prior to Fortress application, irrigate with water to firm soil around plant roots. Allow foliage to dry completely prior to application to prevent granules from sticking. Evenly broadcast Fortress over production area at the directed rate. Irrigate with 1/2 inch of water immediately after application to activate and remove any granules that may be on foliage. Do not reapply at less than 3-month intervals.


For situations where broadcast application of the product is not appropriate, apply the product uniformly over the entire container surface at the rates according to the label.


This product is toxic to fish and highly toxic to other aquatic organisms including oysters and shrimp. Use with care when applying to turf areas adjacent to any body of water. Drift and runoff from treated turf may adversely affect aquatic organisms in adjacent aquatic sites. Do not apply directly to water, or to areas where surface water is present, or to intertidal areas below the mean high water mark. Do not apply when weather conditions favor drift from treated areas. Do not contaminate water when disposing of equipment washwaters.

Groundwater Advisory: This pesticide has properties and characteristics associated with chemicals detected in ground water. This chemical may leach into groundwater if used in areas where soils are permeable, particularly where the water table is shallow.

Surface Water Advisory: This pesticide may impact surface water quality due to runoff of rain water. This is especially true for poorly draining soil and soils with shallow groundwater. This product is classified as having a high potential for reaching surface water via runoff for several months or more after application. A level, well-maintained vegetative buffer strip between areas to which this product is applied and surface water features such as ponds, streams, and springs will reduce the potential loading of isoxaben from run off water and sediment.

(See label for complete list of weeds controlled, application rates and instructions).

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