Simazine (Princep 4L, Princep Caliber)
WSSA Group 5: photosystem II inhibitor
Princep is a soil applied herbicide with efficacy against some grasses and broadleaf wed species.
Apply during the rainy period (from about November 1 to February 15 in eastern Washington) as a single application. Do not apply to frozen ground. Requires surface moisture for activation. Do not apply to vineyards established less than 3 years or to vineyards with shallow, coarse, sandy, or gravelly soils. Serious herbicide injury to grape roots has occurred when applied under improper conditions. Application to vineyards under sprinkler irrigation is hazardous. Do not apply more than 4 lbs of simazine (active ingredient) per acre per year.
At least one weed species resistant to this mode of action documented to occur in ID, OR, or WA; data from Heap, I.
The International Survey of Herbicide Resistant Weeds. Available at www.weedscience.org
Usage for simazine on Grapes
Pre-Emergence (Weeds)
| Target | Rate of application | REI | PHI | MOA | Eff. | Notes |
|---|---|---|---|---|---|---|
| Annual Broadleaf Weeds | 2.2-4.4 lb | 12 | - | 5 | For vineyards established at least 3 years. Princep Caliber 90 (EPA Reg No 100-603) requires a respirator for Mixers and Loaders. | |
| Annual Grasses | 2.2-4.4 lb | 12 | - | 5 | For vineyards established at least 3 years. Princep Caliber 90 (EPA Reg No 100-603) requires a respirator for Mixers and Loaders. |