General Information


Kerb 50WP specialty herbicide is formulated as a wettable powder containing 50% active ingredient packaged in a 1 lb water-soluble pouch.

Kerb 50WP is effective for the control of a wide range of grasses and certain broadleaf weeds. The product is a soil active herbicide with uptake by sensitive weeds occurring through the roots. Before using this herbicide for a specific crop use, study the following general use information that provides important instructions for the safe and effective application of the product.

Use Restrictions: Hand-spray applications of pronamide may be made only to ornamentals and nursery stock of ornamentals.

Chemigation: Do not apply this product through any type of irrigation system except as specified in Dow AgroSciences supplemental labeling.

Weed Spectrum

Kerb 50-W may be used for both preemergence and early postemergence control of winter annual and perennial grasses and chickweed and for preemergence control only of certain other broadleaf weeds and certain other grasses listed.

Note: The weed species controlled by Kerb 50WP are dependent on the rate used, specific crop culture involved, and the associated conditions of temperature, soil type and moisture availability. Refer to specific crop use directions for weed species controlled.

Timing and Application

Unless specific directions are given under the crop to be treated, Kerb 50WP must be applied in the fall or early winter, when temperatures do not exceed 55°F, but prior to freeze-up. Best weed control results occur when Kerb 50WP is applied preemergence to the weeds and when application is followed by rainfall or irrigation to move the product into the root zone of the germinating weeds.

Mix Kerb 50WP thoroughly in clean water at the required concentration and apply uniformly as a spray. For ground application, use a conventional low-pressure herbicide sprayer equipped with flat fan nozzles spaced and calibrated to uniformly deliver 20 to 50 gallons of spray per acre. For aerial applications apply in a coarse droplet spray at 5 to 10 gallons per acre. Accurately calibrate spray equipment prior to each use.

Effect of Soil Type, Moisture and Temperature

Kerb 50WP is most active in coarse to medium textured soils of low organic matter and relatively inactive in peat or muck soils or mineral soils high in organic matter content at rates specified in the label. Herbicidal activity is best in soils containing less than 4 percent organic matter. Use in soils with higher organic matter may result in inconsistent or incomplete weed control.

The herbicidal activity of Kerb 50WP is mainly through root absorption in sensitive weed species. Rain, melting snow or irrigation is essential following treatment to move Kerb 50WP into the root zone of germinating weeds.

Under field conditions, Kerb 50WP will remain relatively stable with little loss of herbicidal activity when soil temperatures are less than 55°F.

As soil temperatures increase, degradation of the active ingredient takes place. Kerb 50WP may degrade rather quickly if left exposed on the soil surface in warm weather. If Kerb 50WP is applied when air temperatures exceed 85°F, the treatment must be soil incorporated to a shallow depth (top two to three inches) or watered into the soil as soon as possible.

Cultural Considerations

For best results apply Kerb 50WP to a trash-free soil surface. Clean cultivation before application is preferable, but not necessary. To obtain optimum weed control in areas not clean cultivated, the area to be treated must be free of surface litter (dead or decaying crop and weed debris, mowing clippings, etc.). Trash-free areas create ideal conditions for rapid movement of Kerb 50WP into the weed root zone following rain or irrigation.

Limitations, Restrictions, and Exceptions


Kerb 50WP is a selective herbicide recommended for the preemergence and postemergence control of annual bluegrass (Poa annua) from warm season grasses and the removal of perennial rye grass (Lolium perenne) from warm season during spring transition. Warm season grasses include ornamental bermudagrass (Cynodon dactylon), Zoysiagrass, St. Augustinegrass and Centipedegrass or bermudagrass grown for seed.

Annual Bluegrass (Poa Annua) Control

Kerb 50WP will control annual bluegrass from pre-germination and seedling stages through tillering, heading and seed formation. Kerb 50WP acts slowly on seedling to mature annual bluegrass. Following application of Kerb 50WP annual bluegrass may first become dark green and then gradually turn yellow and die over a 3- to 5-week period.

For effective control of annual bluegrass in turf or seed crops, moisture is necessary to move Kerb 50WP in the weed root zone. Refer to the Moisture Requirements section of the label for details.

Dosage and Timing

For annual bluegrass control Kerb 50WP is applied at the rate of 1 to 3 lb of product (0.5 to 1.5 lb active ingredient) per acre broadcast application. The dosage rate required is dependent on the growth stage of annual bluegrass at time of application. Follow the dosage rate and timing instructions given.

Annual Bluegrass

One acre equals 43,560 sq. ft.

Use the higher rate when longer preemergence residual control is desired.

Important Note: Avoid spraying on fairways, hillsides, or approaches that may drain onto bentgrass greens or to areas overseeded with sensitive cool season grasses. Do not make an application of a wetting agent for the purpose of frost protection or soil penetration to greens or tees 14 days prior to or after a Kerb 50WP application as injury may result.

Moisture Requirements

Kerb 50WP acts mainly through root absorption in sensitive weed species. If no rainfall occurs within a day or so of the application, a light overhead irrigation should be made to move the chemical into the weed root zone. Avoid heavy irrigations of more than 1 inch to reduce the possibility of excess washing or leaching of the chemical from the area of application.

Kerb Deactivation for Overseeding

Where it is desirable to reseed sooner than 90 days following the application of Kerb 50WP, an application of an activated charcoal such as Gro-Safe, is needed. Apply the activated charcoal at the rate of 10 lb per 1000 sq ft. Allow at least 14 days between the application of Kerb 50WP and the application of charcoal for control of emerged annual bluegrass. Reseed no sooner than 7 days following charcoal application.

Specific Use Restrictions

This product may be used on non-residential seeded, sodded, or sprigged turf or turf grown for seed that is well established. Use of this product on turf that has been weakened by weather-, pest-, disease- chemical-, or mechanical-related stress may increase the chances of turf injury.

This product should only be applied to turf areas that are composed of the following turfgrass species:

- Bermudagrass (Cynodon dactylon)

- Centipedegrass (Eremochloa ophiuroides)

- St. Augustinegrass (Stenotaphrum secundatum)

- Zoysiagrass (Zoysia japonica)

Avoid spraying on hill sides, fairways, or approaches that may drain onto bentgrass greens or to areas overseeded with sensitive cool season grasses. Do not make an application of a wetting agent for the purpose of frost protection or soil penetration to greens or tees 14 days prior to or after a Kerb 50WP application as injury may result.

Do not apply Kerb 50WP herbicide to areas that are to be overseeded with susceptible cool season grasses within 90 days of treatment unless deactivation is planned.

Do not apply Kerb 50WP to dichondra, perennial bluegrass, annual and perennial ryegrasses, fescues and bentgrasses.

Do not graze treated areas and do not feed clippings to livestock.

Restricted Entry Interval

24 hours