Princep Liquid (Simazine 4L)

Princep Liquid (formerly called Simazine 4L), manufactured by Syngenta, is an effective pre-emergent herbicide that prevents many common weeds, including poa annua, ragweed, crabgrass, and over 40 other broadleaf and annual grassy weeds, from developing. 

This liquid pre-emergent herbicide contains the active ingredient simazine, which inhibits photosynthesis in susceptible plants, effectively preventing weed emergence. Its mode of action targets the root systems of germinating weeds, ensuring they do not establish and compete with desired vegetation.

Princep Liquid disrupts the life cycle of various weeds, reducing the need for post-emergent herbicide applications and promoting healthier growth of turfgrass, ornamental plantings, and Christmas tree plantations from lack of weeds. Ensures plants are well-protected for 4-6 months as this pre-emergent herbicide continues to prevent weeds from germinating in the soil during this time. 

Tools Needed

For a small-volume application, you can use a handheld pump sprayer, a backpack sprayer, or a hose-end sprayer. You can apply large-volume applications using a professional skid sprayer.

How to Use

• Step 1: Determine how much Princep Liquid to use by measuring the square footage of the treatment area. To do this, measure the length and width of the treatment area in feet, then multiply them together (length X width = square footage). Princep Liquid should be applied at a rate of 0.75 to 1.5 fl. oz. in a gallon of water per 1,000 sq. ft. on turfgrass. For large-volume applications, apply 1 to 2 quarts of product per 20 gallons of water per acre. Refer to the product label for specific application rates and restrictions.
• Step 2: Fill your sprayer halfway with water. Measure the required amount of product and add it to the sprayer. Fill your sprayer with the rest of the water, thoroughly agitate it, and you’re ready to apply.
• Step 3: Apply the product over the desired area, preferably on a fan spray setting, for uniform coverage. Reapply as needed, following label instructions regarding your application type.

Where to Use

Princep Liquid can be applied to nurseries, Christmas tree plantings and shelterbeds, and turfgrass for sod. It may also be applied to turfgrass for fairways, lawns, and similar areas. 

For turf, apply only to Bermudagrass, Centipedegrass, St. Augustinegrass, and Zoysiagrass.

When to Use

Apply after September 1 (after October 1 for annual bluegrass) before the emergence of winter annual weeds. For control of summer annual weeds, apply this product in late winter before the weeds emerge.

For control of summer annuals that emerge after the initial application, apply at least 30 days after the initial application but not after June 1. However, do not make more than 2 applications per calendar year.

Safety Information

Princep Liquid is safe to use around children and pets when applied according to the product label instructions. Always wear the proper personal protective equipment (PPE) when mixing and applying this product.

Allow children, pets, and workers to enter treated areas after 48 hours have passed after the application. 

It is important to prevent this product from drifting into non-target areas, as it can contaminate water or harm non-target plants.

Special Considerations

It is recommended not to apply Princep Liquid to sand and loamy sand soils because the active ingredient Simazine can travel or leach through soil and can enter groundwater.