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Sencor STZ - Enjoy More Grower Vacations

Sencor STZ


New Sencor® STZ herbicide for potatoes lets you spend less time worrying about weeds, and more time enjoying the little things. Things like taking in the stars, meeting the school bus, or pausing to pat the dog. We call those Grower Vacations. And with the all-new weed control of new Sencor STZ, you can discover more of them knowing you’re protected from all major weeds. So enjoy your own vacation, even if it’s just for a few minutes.

Product Summary


Product Type

  • Herbicide


  • Potatoes


  • Broadleaf & Grass Weeds
Weeds Surpressed

Weeds Controlled (Top 6)

  • Barnyard Grass
  • Cheat Grass
  • Crab Grass
Groups and Active Ingredients

Groups and Active Ingredients

  • Metribuzin Group 5
  • Sulfentrazone Group 14 
Formulation Type

Formulation Type

  • Suspension Concentrate Flowable


  • 7.5Kg+1.95L

Key Product Points

  • Combines the trusted power of Sencor with a new active ingredient, sulfentrazone, for exceptional control of all major weeds.
  • Applied by ground, pre-emerge to potatoes for enhanced broad-spectrum broadleaf and grassy weed control.

Sencor STZ herbicide combines the trusted power of Sencor with a new active ingredient, sulfentrazone, for exceptional control of all major weeds. It’s applied by ground, pre-emerge to potatoes for enhanced broad-spectrum broadleaf and grassy weed control with activity on triazine, glyphosate, linuron and Group 2 resistant weeds. It has activity on emerged weeds and provides residual broad-spectrum control to weeds yet to germinate. 

2015 Ontario Research Authorization Results – % Overall Weed Control (at 43 and 62 Days After Application (DAA)) Sencor STZ weed control by application timing 2016 Ontario Research Authorization Results - % Control of Lamb’s-quarters and Pigweed species Sencor STZ herbicide for control of lamb’s quarters and pigweed


Active Ingredients

Group 5 Group 14
Group 5
Group 14



Weeds Controlled

GRASS WEEDS including:
Barnyard grass
Cheat grass
Crab grass
Fall panicum
Giant foxtail
Green foxtail
Johnson grass (seedling)
Witch grass
Yellow foxtail

Common chickweed
Common ragweed
Dandelion (seedling)
Green smartweed
Kochia (STZ high rate only)
Prickly mallow
Prostrate pigweed
Redroot pigweed
Russian thistle
Shepherd’s purse
Wild buckwheat
Wild mustard
Wild potato vine
Yellow woodsorrel

Including triazine, glyphosate, linuron and Group 2 resistant weeds listed above.

Provinces of Registration

British Columbia
New Brunswick
Nova Scotia
Prince Edward Island

Application Tips

  • Applications of Sencor STZ must be made during the pre-emerge stage, to prevent injury to emerging potato seedlings
    • A minimum of one inch of soil must cover emerging potato shoots at application. If application is delayed, injury may occur if potato seed pieces are germinating or if they are located near the soil surface.
    • After a hilling event, allow the soil to settle or crust before application
    • Avoid soil disturbance, including hilling, after application. If hilling is required after application it is recommended to wait as long as possible after application.
  • Sencor STZ requires a small amount of rainfall within 10-14 days of application to be activated
  • Sencor STZ is recommended for soils with organic matter content between 1.5% and 6%, and soils with a pH of less than 7.8. See label for further information.
  • Use higher rates for:
    • longer season potatoes
    • situations where longer control is required and weed infestations are heavy
    • soils with a pH less than 7.0 and organic matter greater than 3%


Restricted Entry Interval (REI)
  • 12 hours


Pre-harvest interval (PHI)
  • 60 days


Maximum Applications
  • STZ (sulfentrazone) should not be applied to the same field in consecutive years



Available in a convenient co-pak

  • Sencor 75DF –75% dry flowable
  • STZ – 480 g/L flowable


  • Registered application rate: 600-800 g/ha (243-324 g/ac.) of Sencor and 157-219 mL/ha (64-89 mL/ac.) of STZ 1,2


Application Timing
  • For pre-emergence applications only


Water Volumes


  • 100 to 300 L/ha (10-30 US gal/ac.)


  • 6 hours after application


Re-cropping Intervals
  • Potatoes can be replanted at any time following an application of STZ

STZ re-cropping intervals

Rotational Crop Replant Interval (Months)
Alfalfa 12
Barley 12
Canola 12
Chickpea Anytime
Corn, field 12
Corn, sweet and pop 24
Field pea Anytime
Flax Anytime
Lentils 24
Potatoes Anytime
Sorghum 24
Soybeans Anytime
Sunflowers Anytime
Spring and Durum wheat 12
Winter wheat 4

SENCOR 75 DF Herbicide may injure rotational crops:

  • Rotation crops such as onions, celery, peppers, cole crops, lettuce and spinach, sugar beets, table beets and turnips, pumpkin and squash, cucumbers and melons, tobacco, and non-triazine tolerant canola (rapeseed) are sensitive to SENCOR 75 DF Herbicide and may be injured if planted in soil treated with SENCOR 75 DF Herbicide during the year of application or the following crop year.
  • Fall seeded or cover crops such as wheat, oats, and rye may be injured when seeded within the same season as the application of SENCOR 75 DF Herbicide.


Residue and Grazing Intervals
  • Do not harvest potatoes within 60 days of application

1 This tank-mix will also provide control of ALS and glyphosate resistant weeds and control of Kochia, when STZ is applied at 219 mL/ha.
2 Do not use on soils with a pH of 7.8 or greater. See label for the proper rates of application according to soil texture, organic matter content and pH.

Resistance Management

To delay herbicide resistance:

  • Where possible, rotate the use of STZ Herbicide or other Group 14 herbicides within a growing season (sequence) or among growing seasons with different herbicide groups that control the same weeds in a field
  • Use tank mixtures with herbicides from a different group when such use is permitted. To delay resistance, the less resistance-prone partner should control the target weed(s) as effectively as the more resistance-prone partner
  • Herbicide use should be based on an integrated weed management program that includes scouting, historical information related to herbicide use and crop rotation, and considers tillage (or other mechanical control methods), cultural (for example, higher crop seeding rates; precision fertilizer application method and timing to favour the crop and not the weeds), biological (weed-competitive crops or varieties) and other management practices
  • Monitor weed populations after herbicide application for signs of resistance development (for example, only one weed species on the herbicide label not controlled). If resistance is suspected, prevent weed seed production in the affected area if possible by an alternative herbicide from a different group. Prevent movement of resistant weed seeds to other fields by cleaning harvesting and tillage equipment when moving between fields, and planting clean seed
  • Have suspected resistant weed seeds tested by a qualified laboratory to confirm resistance and identify alternative herbicide options
  • Contact your local extension specialist or certified crop advisors for any additional pesticide resistance-management and/or integrated weed-management recommendations for specific crops and weed biotypes


Exceptional Resistance Management
  • Any weed population may contain or develop plants naturally resistant to STZ Herbicide and other Group 14 herbicides. The resistant biotypes may dominate the weed population of these herbicides are used repeatedly in the same field. Other resistance mechanisms that are not lined to site of action, but specific for individual chemicals, such as enhanced metabolism, may also exist. Appropriate resistance-management strategies should be followed.


What is Resistance?

Resistance is a naturally occurring, inherited ability of some weed biotypes to survive a herbicide treatment that should, under normal use conditions, effectively control a weed population. Some herbicide-resistant weeds have naturally developed one or more mechanisms that allow them to survive a herbicide treatment.

Single, cross, and multiple herbicide resistance chart

For a weed to be considered resistant it must:

  • Normally be controlled by the herbicide
  • Survive a usually lethal dose of the herbicide
  • Be heritable, meaning it is passed from generation to generation

Herbicide-resistant individuals are naturally present within a weed population at very low frequencies.

What's the Impact to Farming in Canada?

Why is it important to you?

The management issues and yield concerns with herbicide resistance are very real, especially now with an increasing number of herbicide-resistant weeds spreading across Canada.

Loss of viable herbicide options

  • Have to rely on currently available herbicides for the foreseeable future
  • No herbicides with new modes of action are in advanced trials

Would require changes in weed and crop management practices

  • Zero or reduced tillage rely heavily on herbicides for weed control

Reduced return on investment

  • Increase the cost of weed management
  • Loss of yield potential

The number of weeds with herbicide resistance continues to rise

  • Including weeds resistant to multiple modes of action

Development of Herbicide Resistance

How does resistance develop?

The image below demonstrates the interaction between a weed species and a particular mode of action and the development of herbicide resistance at different speeds. It’s clear to see that over time the use of a herbicide quickly changes from being very effective to becoming extremely ineffectual. In fact, by the fifth year of application the herbicide is failing to eliminate herbicide-resistant weeds. It is particularly alarming that there is a dramatic increase in failure rate from the fourth to fifth season.

How herbicide resistance develops chart
% Resistant Weeds in Population Weed Control
0 Application .0001% Excellent
1st Application .00143% Excellent
2nd Application .0205% Excellent
3rd Application .294% Excellent
4th Application 4.22% Excellent
5th Application 60.5% Failure
Source: Weed Science Society of America, 2011

What can you do to delay the onset of herbicide resistance?

  • Don’t rely solely on herbicides for weed control
  • Develop field-specific long-term weed management plans
  • Rotate herbicide groups year over year

General Guidelines for herbicide rotations:

  • Avoid repeated use of the same herbicide or herbicides having the same Group in the same field year to year
  • Limit the number of applications of a single herbicide or herbicides having the same site of action in a single growing season
  • Use mixtures or sequential treatments of herbicides having different Groups, which are active on the same target weeds whenever possible
  • Use non-selective herbicides pre-seed or pre-emergence to control early flushing weeds (prior to crop emergence) and/or weed escapes

Resistant Weed Management Strategies

  2. Rotate crops as often as possible to utilize the unique modes of action available within the crop

  4. Time and place fertilizer to benefit your crop, not weeds

  6. Systematically target problem weeds and respond quickly to changing weed populations

  8. Scout often and take note of individual weed response to all applications (pre-emergent, post-emergent and pre-harvest)

  10. Make sure you remove all weeds before they set seed – even if you have to pull by hand. Remember the old English proverb: One year seeding, seven years weeding

  12. Leaving a 1m wide weed-free zone around your cropping fields (so new weeds can’t propagate and expand throughout your fields)

  14. Decrease your row spacing and increase seeding rates to optimize plant populations, maximize crop competitiveness and minimize time to crop canopy closure

    • Match selection of herbicide(s) with your most difficult weeds
    • Use full-labelled rates
    • Include the best tank mixes and adjuvant(s)
    • Use correct spray volume (follow label directions)
    • Use correct nozzle spacing and droplet size
    • Don’t spray at excess travel speeds, follow label directions
    • Apply during the best weather conditions (warm, humid, and sunny conditions with minimal wind)
    • Maximize rainfastness intervals
    • Time of day (herbicides are most effective when sprayed between 8:00am and 9:00pm)

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