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.

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


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.


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