44781*†Princep, *†Princep Caliber 90, *Simazine Flowable, others
Common Name: simazine
Formulations: 4L, 90WDG, others
Newer registrations of †Princep 4L, Liquid and †Caliber 90 no longer allow use in Nassau and Suffolk Counties. Other products containing simazine have not changed.
Uses: Preemergent control of many annual broadleaf and grass weeds in established field grown woody nursery stock and Christmas trees.
| Amount of active ingredient | Amount by formulation |
| | 4L | 90WDG |
Per Acre | 2 to 4 lb. | 2 to 4 qt. | 2.2 to 4.4 lb. |
Per 1,000 sq. ft. | | 1.5 to 3 fl. oz. | 0.8 to 1.6 oz. |
Major Weeds Controlled: Many annual broadleaf weeds including chickweed, wild mustards, pigweed, lambsquarters, groundsel, ragweed, and others. Annual grasses such as crabgrass, panicum, and foxtail are more tolerant but are controlled at the higher rates.
Major Weeds Not Controlled: Late-germinating summer annual grasses are often not controlled. Annual bluegrass is labeled but control is variable. Many species have developed biotypes resistant to simazine including groundsel, lambsquarters, ragweed, and pigweed.
For Best Results: Apply before weed germination. Moisture, 1 to 2 inches of irrigation, or shallow cultivation is needed to move herbicide to the root zone for optimal activity.
Cautions and Precautions: Use lower rates on coarse textured soil and soil low in organic matter. In nurseries, do not apply for at least one year after transplanting. To avoid injury to Christmas trees, do not use on seedbeds or cutting beds. Do not apply to Christmas trees less than two years old. Do not use until soil is firmly settled around roots. Do not apply more than 4 lb. AI per acre per year. Do not apply more than once a year except as directed for quackgrass control. See label for reduced use rates on some species. Simazine can leach through soil and can enter groundwater that may be used as drinking water. Do not apply simazine to sand and loamy sand soils where the water table is close to the surface and where soils are very permeable. If herbicide resistant biotypes of weeds listed on the label are suspected, use this product in registered combination or in sequence with other registered products that are not triazines (Group 5 herbicides).
Residual Activity: Three to six months of broadleaf weed control can be expected, depending on rate, soil type, and environmental conditions.
Volatility and Leaching Potential: Essentially nonvolatile. Moderate leaching potential. Leaching can occur on coarse-textured soils. Movement as surface runoff may also occur when heavy rains follow applications.
Symptoms and Mode of Action: Absorbed mostly through the roots. Translocated upward to mature leaves and growing points. Inhibits photosynthesis. Weed seedlings may emerge from the soil then turn yellow and die. Symptoms of injury on nursery stock include interveinal chlorosis, resembling iron chlorosis, marginal chlorosis and necrosis, reduced vigor, and general chlorosis of the new growth. Classified as a Group 5 Herbicide.
Manufacturers: Syngenta
Loveland Products
EPA Reg. Nos.: *†Princep 4L: 100-526
*†Princep Caliber 90WDG: 100-603
*Simazine Flowable 4L: 34704-687
*Restricted use pesticide.
†Not for use in Nassau and Suffolk Counties.