J from Nickelsville, Va writes
Princep Liquid Herbicide is a pre-emergent weed control product and it will not control the weeds that have already emerged in your yard. According to the Princep product label: Apply Princep Liquid after September 1 (after October 1 for annual bluegrass) before emergence of winter annual weeds. Fall applications of Princep Liquid will control annual bluegrass, burclover, lawn burweed, common and mouseear chickweed, corn speedwell, henbit, hop clover, spurweed, and parsley-piert. Princep Liquid will also control these weeds soon after emergence. For control of summer annual weeds listed in the Product Information section of this label, apply Princep Liquid in late winter before the weeds emerge. Apply in a minimum of 15 gallons of water per acre. Irrigate with 1/2 inch of water if rainfall does not occur within 10 days after preemergent treatment. Where annual bluegrass is the major weed, use 1 qt. of Princep Liquid per acre (22 ml or 0.75 fl. oz./1,000 sq. ft.). Use 1-2 qt./A Princep Liquid (22-44 ml or 0.75-1.5 fl. oz./1,000 sq. ft.) for control of other weeds. However, do not exceed 1 qt./A of Princep Liquid per treatment on newly sprigged turf grass or on hybrid Bermuda.
For control of summer annuals which emerge after the initial application, apply an additional 1 qt./A Princep Liquid at least 30 days after the initial application, but not after June 1. However, do not make more than 2 applications per year.
We do not recommend applying RoundUp to the area because it is a non-selective herbicide that will eradicate anything that is sprayed with the product. Including the desired vegetation.
Answer last updated on: 07/21/2014