rows of young potatoes


  • Herbicide


  • 2

Potato and field tomato growers look to Prism SG herbicide for its outstanding post-emergent control of key weeds such as: quackgrass, redroot pigweed, barnyard grass, fall panicum, green foxtail, hairy nightshade, lamb’s-quarters (suppression), witchgrass and yellow foxtail.


Prism SG herbicide can be used for post-emergent control on all types of potatoes. This includes seed potatoes, early maturing varieties and (in Western Canada) irrigated potatoes.


Both processing and fresh market tomatoes can be treated with Prism SG.

Weeds controlled

At the 24 g/ac (60 g/ha) rate, Prism SG controls quackgrass, redroot pigweed, barnyard grass, fall panicum, green foxtail, hairy nightshade (in tomatoes), lamb’s-quarters (suppression), witchgrass and yellow foxtail.


Below lists the crops that Prism SG herbicide can be used on.


Blueberry, Highbush (Vaccinium corymbosum)


Caneberry (Rubus spp. L)


Potato (Solanum tuberosum ssp. Tuberosum)


Tomato (Lycopsersicon esculentum)


Now registered in the following provinces:

  • Registered
  • Unregistered

Technical Specifications

  • Approved Use
    Refer to the Prism SG label for complete use instructions.
    Refer to the Controlled Weeds list for the full list of weeds.

    Weeds Controlled (at 60 grams per hectare)
    • Lamb's-Quarters(†)
    • Quackgrass(1)
    • Yellow Foxtail(2)
    (†) Suppression only. Weed suppression is a visual reduction in weed competition (reduced population and/or vigour) as compared to an untreated check. Degree of suppression will vary with size of weed and environmental conditions prior to and following treatment.
    (1) Quackgrass - Apply Prism™ SG Herbicide with a recommended surfactant postemergence when the majority of the quackgrass shoots are actively growing and in the 3 to 6 leaf stage (<25cm - leaf extended). Annual grasses not emerged at the time of Prism™ SG Herbicide application to quackgrass will not be controlled. Application to quackgrass prior to the 3 to 6 leaf stage may result in reduced weed control since the majority of shoots may not have emerged.
    (2) Yellow foxtail present at the time of Prism™ SG Herbicide application will be controlled. Any yellow foxtail emerging after application will not be controlled.
  • Rates
    • One 480 g bottle of Prism SG herbicide treats 20 acres (8 ha).
    • Tomatoes - 24 g/ac (60 g/ha)
    • Apply 60 grams/ha of Prism SG herbicide as a broadcast spray, with a recommended surfactant, to potatoes prior to initiation of flowering.
  • Application Timing

    Apply to weeds according to the leaf staging indicated below.

    Weed Leaf Staging at Application
    Annual grasses 1 to 6 leaf stage (up to early tillering – two 2-leaf tillers)
    Quackgrass Apply to actively growing shoots in the 3 to 6 leaf (< 25 cm leaf extended) stage
    Lamb's-quarters, Redroot Pigweed 4 to 6 leaf stage (< 10 cm tall or across)

    Application to control ANNUAL GRASSES and QUACKGRASS must be made before the crop canopy can interfere with spray coverage of the target weeds.
    Cultivation is NOT recommended within 7-10 days prior to or after application of Prism™ SG Herbicide.
  • Mixing Instructions
    1) Fill clean tank about 1/3 full of clean water.
    2) With the agitator running, add the required amount of Prism™ SG herbicide. Continue to agitate for a minimum of 5 minutes to ensure that Prism™ SG herbicide is completely dissolved.
    3) Make sure there are no un-dissolved granules, and then add the required amount of the tank mix partner.
    4) After Prism SG Herbicide has been well mixed and is in suspension, add a recommended non-ionic surfactant such as CITOWETT* PLUS, AGRAL* 90, or AG-SURF* at 2 L per 1000 L spray solution (0.2% v/v).
    5) Fill the remainder of the spray tank with water.
    For repeat tank loads, reduce the material remaining in the tank to 10% of the original volume or less before proceeding with step 1, because remaining chemicals may prevent Prism SG herbicide granules from completely dissolving. If this is not possible, pre-slurry the Prism™ SG herbicide in a small amount (5-10 L) of water before adding to the tank.
    Agitation is required for uniform mixing and application. Apply Prism SG Herbicide in a minimum of 100 litres of water per hectare. Flat fan nozzles are recommended. Use a spray pressure of 175 - 275 kPa.
    Use 50 mesh screens or larger. Use spray preparation of Prism™ SG Herbicide within 24 Hours or product degradation may occur resulting in a loss of weed control. Use vigorous agitation to thoroughly disperse spray mixtures that have been allowed to stand in the tank.
    NOTE: Prism SG Herbicide will degrade in acidic or highly alkaline water. Mix no more than can be used in one day. If spraying is interrupted, thoroughly re-agitate the spray mixture before resuming spraying.
    Calibrate sprayers only with clean water away from well sites. Make scheduled checks of spray equipment. Assure accurate measurement of products. Mix only enough product for the job at hand. Avoid overfilling spray tank.
  • Herbicide Group

    Group 2

  • Tank Mixes

    Apply a tankmix of Prism SG herbicide plus Tricor 75DF Herbicide postemergent plus a non-ionic surfactant, i.e. Citowett Plus, Agral 90 or AgSurf at 2L per 1000L of spray solution (0.2% v/v) in potatoes for control of annual grasses and broadleaf weeds. Tricor 75 DF herbicide should be applied at 280-375 g/ha along with Prism SG herbide at 60 g/ha to control all weeds listed on both Prism SG Label and Tricor 75 DF herbicide label.


    1)  Apply specified dosage per hectare as a broadcast postemergence spray over the tops of potatoes when they are less than 10 cm high. Do not use postemergence treatments on Atlantic, Eramosa, Shepody, red-skinned or any early maturing varieties.  Temporary yellowing or leaf burn may occur, especially if crop is under stress from poor growing conditions such as periods of cool, wet, and cloudy weather. Avoid postemergence application under these conditions.

    2)  Spray before weeds are 4 cm high. Use high rates for grasses or dense broadleaf weeds.

    3)  Do not harvest within 60 days of application.

    4)  Apply to actively growing annual grasses at the full 2-leaf to 5-leaf stages. For green and yellow foxtail, apply at full 2-leaf to 4-leaf stage.

    5)  Apply to actively growing plants that have 3 to 5 fully developed leaves.

    6)  Spray before broadleaf weeds are 4 cm high and when annual grasses are 1 to 6 leaf stage (up to early tillering – two 2-leaf tillers).

    7)  Prism Herbicide must be applied with a recommended non-ionic surfactant, i.e. Citowett Plus, Agral 90 or Agsurf at 2 L per 1000 L of spray solution (0.2% v/v).

Weeds steal light, water and nutrients from healthy plants, decreasing the yield and quality of your potato crop.

Read More

Strategies for Protecting Potato Crops from Key Weeds




Before use and for complete product information, please read and follow label directions.

Horticulture Crop Protection Guide
View a comprehensive listing of Corteva Agriscience horticulture products.