General Information


CHISUM is recommended for use on land primarily dedicated to the production of pasture, rangeland, or established grasses in the Conservation Reserve Program (CRP). This product may also be used on selected uncultivated areas (fence rows, farmyards, and rights-of-way) directly adjacent to, or which transect or pass through, treated pastures, rangeland, or CRP, where grazing or harvesting for animal feed of those uncultivated areas may occur.

CHISUM is a dispersible granule that controls or suppresses broadleaf weeds and brush in pasture, rangeland and CRP. CHISUM is mixed in water or can be preslurried in water and added to liquid nitrogen carrier solutions and applied as a uniform broadcast spray. A spray adjuvant must be used in the spray mix unless otherwise specified on the label.

CHISUM is a broad-spectrum herbicide recommended for use on pastures, rangeland or CRP in most states. Check with your state extension or Department of Agriculture before use to be certain CHISUM is registered in your state. Do not use CHISUM in the following counties of Colorado: Alamosa, Conejos, Costilla, Rio Grande, and Saquache.

CHISUM controls weeds by preemergence and postemergence activity. For best results, apply CHISUM to young, actively growing weeds. Weeds hardened off by cold weather or drought stress may not be controlled. The use rate depends upon the weed spectrum and size of weeds at application. The degree and duration of control may depend on the following factors:

- weed spectrum and infestation intensity

- weed size at application

- environmental conditions at and following treatment

It is permissible to apply CHISUM to floodplains where surface water is not present, terrestrial areas of deltas, and low lying areas where water is drained but may be isolated in pockets due to uneven or unlevel conditions.

Environmental Conditions and Biological Activity

CHISUM is absorbed through the foliage and roots of broadleaf weeds, rapidly inhibiting their growth. Leaves of susceptible plants appear chlorotic from 1 to 3 weeks after application and the growing point subsequently dies. The final effects on annual weeds are evident about 4 to 6 weeks after application. The ultimate effects on perennial weeds and woody plants occur in the growing seasons following application.

One to two inches of rainfall or sprinkler irrigation (enough to wet the top 2-3 inches of soil profile) is needed to move CHISUM into the weed root zone before the next flush of weeds emerge. The amount of moisture required for sufficient activation increases with crop or weed residue and for finer textured soils. Without sufficient rainfall or sprinkler irrigation to move CHISUM into the weed root zone, weeds that germinate after treatment will not be controlled.

Application of CHISUM provides the best control in vigorously growing grasses that shade competitive weeds. Weed control in areas of thin grass may not be as satisfactory. However, a grass canopy that is too dense at application can intercept spray and reduce weed control.

CHISUM is safe to desirable grass species under normal conditions. However, grasses that are stressed from adverse environmental conditions (such as extremes in temperatures or moisture), abnormal soil conditions, or cultural practices, may be injured by applications of CHISUM. In addition, different species of grass crops may be sensitive to treatment with CHISUM under otherwise normal conditions. Application of CHISUM to these species may result in injury.

In warm, moist conditions, the expression of herbicide symptoms is accelerated in weeds and brush; in cold and/or dry conditions, expression of herbicide symptoms is delayed. In addition, weeds and brush hardened-off by drought stress are less susceptible to CHISUM.

Weed and brush control or suppression may be reduced if rainfall, sprinkler irrigation or snowfall occurs within 4 hours after application.


CHISUM should not be used on soils having a pH above 7.9, because soil residual activity could extend crop rotation intervals beyond normal. Under certain conditions, CHISUM could remain active in the soil for 34 months or more, injuring subsequent crops.

Checking Soil pH

Before using CHISUM, determine the soil pH of the areas of intended use. To obtain a representative pH value for the test area, take several 0 inch to 4 inch samples from different areas of the field and analyze them separately. Consult local extension publications for additional information on recommended soil sampling procedures.


A field bioassay must be completed before rotating to any crop or grass species/variety not listed in the Rotation Intervals Table, or if the soil pH is not in the specified range, or if the use rate applied is not specified in the table. To conduct a field bioassay, grow test strips of the crop(s) or grass(es) you plan to grow in fields previously treated with CHISUM. Crop or grass response to the bioassay will indicate whether or not to rotate to the crop(s) or grass(es) grown in the test strips. If a field bioassay is planned, check with your local Agricultural dealer for information detailing the field bioassay procedure.


There are no grazing or hay harvest restrictions for CHISUM when applied to range, pasture, CRP, and/or undesirable vegetation in uncultivated areas (fence rows, farmyards, and rights-of-way) which are adjacent to, or pass through or transect, treated pastures, rangeland, or CRP.

Coveralls and shoes plus socks must be worn if cutting within 4 hours of treatment.


When herbicides that affect the same biological site of action are used repeatedly over several years to control the same weed species in the same field, naturally-occurring resistant biotypes may survive a correctly applied herbicide treatment, propagate, and become dominant in that field. Adequate control of these resistant weed biotypes cannot be expected. If weed control is unsatisfactory, it may be necessary to retreat the problem area using a product affecting a different site of action.

To better manage herbicide resistance through delaying the proliferation and possible dominance of herbicide resistant weed biotypes, it may be necessary to change cultural practices within and between crop seasons such as using a combination of tillage, retreatment, tank-mix partners and/or sequential herbicide applications that have a different site of action. Weed escapes that are allowed to go to seed will promote the spread of resistant biotypes.

It is advisable to keep accurate records of pesticides applied to individual fields to help obtain information on the spread and dispersal of resistant biotypes. Consult your agricultural dealer, consultant, applicator, and/or appropriate state agricultural extension service representative for specific alternative cultural practices or herbicide recommendations available in your area.


This product may be used as part of an Integrated Pest Management (IPM) program that can include biological, cultural, and genetic practices aimed at preventing economic pest damage. IPM principles and practices include field scouting or other detection methods, correct target pest identification, population monitoring, and treating when target pest populations reach locally determined action thresholds.

Consult your state cooperative extension service, professional consultants or other qualified authorities to determine appropriate action treatment threshold levels for treating specific pest/crop systems in your area.


- CHISUM may cause injury to desirable trees and plants when contacting their roots, stems or foliage. These plants are most sensitive to CHISUM during their development or growing stage. FOLLOW THE PRECAUTIONS IN THE LABEL WHEN USING CHISUM.

- Injury to or loss of desirable trees or vegetation may result from failure to observe the following:

a. Do not apply CHISUM, or drain or flush equipment on or near desirable trees or other plants, or on areas where their roots may extend, or in locations where the chemical may be washed or moved into contact with their roots.

b. Do not use on lawns, walks, driveways, tennis courts, golf courses, athletic fields, commercial sod operations, or other high-maintenance, fine turfgrass areas, or similar areas.

c. Do not use on grasses grown for seed.

- Do not contaminate irrigation ditches or water used for domestic purposes.

- Do not apply to irrigated land where the tailwater will be used to irrigate crops.

- Do not apply to frozen ground as surface runoff may occur.

- Do not apply to snow-covered ground.

- Grass species or varieties may differ in their response to various herbicides. Cheminova recommends that you first consult your state experiment station, university, or extension agent as to sensitivity to any herbicide. If no information is available, limit the initial use of CHISUM to a small area. Components in a grass seed mixture will vary in tolerance to CHISUM so the final stand may not reflect the seed ratio.

- Under certain conditions such as heavy rainfall, high pH, prolonged cold weather, or wide fluctuations in day/night temperatures prior to or soon after CHISUM application, temporary discoloration and/or grass injury may occur. CHISUM should not be applied to grass that is stressed by severe weather conditions, drought, low fertility, water-saturated soil, disease, or insect damage, as grass injury may result. Severe winter stress, drought, disease, or insect damage before or following application also may result in grass injury.

- Applications of CHISUM to pastures, rangeland or CRP undersown with legume crops may cause severe injury to the legumes. Legumes in a seeding mixture may be severely injured or killed following an application of CHISUM.

- Treatment of powdery, dry soil or light, sandy soil when there is little likelihood of rainfall soon after treatment may result in off target movement and possible damage to susceptible crops when soil particles are moved by wind or water. Injury to crops may result if treated soil is washed, blown, or moved onto land used to produce crops. Injury may be more severe when the crops are irrigated. Do not apply CHISUM when these conditions are identified and powdery, dry soil or light or sandy soil are known to be prevalent in the area to be treated.

- Applications made where runoff water flows onto agricultural land may injure crops. Applications made during periods of intense rainfall, to soils saturated with water, or soils through which rain fall will not readily penetrate may result in runoff and movement of CHISUM. Treated soil should be left undisturbed to reduce the potential for CHISUM movement by soil erosion due to wind or water.

- For ground applications applied to weeds when dry, dusty field conditions exist, control of weeds in wheel track areas may be reduced.

- Do not apply more than the equivalent of 1 ounce of chlorsulfuron per acre per year.

- Do not apply more than the equivalent of 1 ounce of metsulfuron methyl per acre per year.

- Avoid disturbing (e.g. cultivating or mowing) treated areas for at least 7 days following application.

- Do not apply this product through any type of irrigation system.


Limitations, Restrictions, and Exceptions


Use Rates for Pastures and Rangeland

Application Timing—Pastures and Rangeland

CHISUM may be used on established native grasses such as bluestems, blue grama, buffalograss and other pasture grasses such as bermudagrass, bluegrass, orchardgrass, bromegrass (except Matua bromegrass) and fescue. Specific application information on several of these pasture grasses follows.

Do not use on bentgrass or susceptible grass pastures such as timothy, carpetgrass, Matua bromegrass or St. Augustine grass.

Applications of CHISUM may cause severe injury to and/or loss of Pensacola bahiagrass, ryegrass (Italian or perennial) and Garrison’s creeping foxtail pastures.

Buffalograss Precautions:

Do not use CHISUM on buffalograss that has been established for less than one year or on stands grown for seed production. Do not apply more than 0.625 ounces per acre of CHISUM to buffalograss.

Fescue Precautions:

Note that CHISUM may temporarily stunt fescue, cause it to turn yellow, or cause seedhead suppression. To minimize these symptoms, take the following precautions:

- do not use more than 0.5 ounces per acre of CHISUM

- use a non-ionic surfactant at 1/2 to 1 pint per 100 gallons of spray solution (1/16 to 1/8% v/v). Do not use a spray adjuvant other than non-ionic surfactant.

- make application later in the spring after the new growth is 5 to 6 inches tall, or in the fall

- do not use surfactant when liquid nitrogen is used as a carrier

The first cutting yields may be reduced due to seedhead suppression resulting from treatment with CHISUM.

Other Pasture and Rangeland Grasses: Varieties and species of forage grasses differ in their tolerance to herbicides. When using CHISUM on a particular grass for the first time, limit use to a small area. If no injury occurs throughout the season, larger acreage may be treated the following season. Broadleaf pasture species, such as alfalfa and clover, are highly sensitive to CHISUM and will be severely stunted or injured by CHISUM.


CHISUM is recommended for the control or suppression of broadleaf weeds in established stands (planted previous year, or earlier) of the following perennial native or improved grasses grown on land enrolled in the Conservation Reserve Program (CRP).

Because newly planted CRP grass stands do not sufficiently compete with weeds, and because weed pressure in CRP fields is often severe, performance from CHISUM may not always be satisfactory. An additional herbicide application or mowing may be needed.

Application Timing and Use Rates for CRP

CHISUM may be applied postemergence at 0.125 to 0.25 ounces per acre to labeled grasses listed above that were planted the previous season and are fully tillered.

Restricted Entry Interval

4 hours

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