NC State Extension Publications


Skip to Introduction
Trade Name: Regal O-O Common Name: oxyfluorfen + oxadiazon Formulation: 3 G (2 +1)

Preemergence weed control in container grown ornamentals, including conifer seedlings. Also labeled for use in field nurseries and landscape plantings. Particularly useful when one wishes to avoid the use of root-inhibiting herbicides.

Amount of Active Ingredient Amount by Formulation
Per Acre 3 lb ai/A (2+1) 100 lb
Per 1,000 sq. ft. 2.3 lb

Major Weeds Controlled

Skip to Major Weeds Controlled

Many annual grasses and broadleaf weeds including annual bluegrass, goosegrass, bittercress, chickweed, willowherb, groundsel oxalis, horseweed, and others.

Major Weeds Not Controlled

Skip to Major Weeds Not Controlled

Nutsedges & other established perennial weeds. Weak on spurge, chickweed, pearlwort, eclipta.

For Best Results

Skip to For Best Results

Apply before weed emergence or remove existing weeds before treatment. Apply to dry foliage. Irrigate immediately after application.

Cautions and Precautions

Skip to Cautions and Precautions

Granules may adhere to wet or hairy leaves and cause injury. Do not apply to plants such as yucca, hosta, or daylily that have leaves that may funnel granules to the base. Do not use in greenhouses or on herbaceous ornamentals. Allow several weeks between application and covering for winter protection or shipping in an enclosed trailer. For use by professional applicators only, not for homeowner or consumer sale.

Residual Activity

Skip to Residual Activity

Eight to ten weeks of residual preemergence weed control may be expected, depending upon substrate, irrigation practices, and season. Shorter residual is to be expected in container crops compared to soil applications.

Volatility and Leaching Potential

Skip to Volatility and Leaching Potential

Moderate volatility and low leaching potential. However, do not use in enclosed structures as volatilization is possible.

Symptoms and Mode of Action

Skip to Symptoms and Mode of Action

Oxyfluorfen and oxadiazon are both contact-type herbicides affecting primarily shoot growth. Injury symptoms on ornamentals generally consist of contact-type burn where granules adhere to the foliage. Mode of action for both active ingredients: HRAC Group E; WSSA Group 14.

Additional Information

Skip to Additional Information
Worker Protection Standards REI: 24 hours (longer in Christmas trees)
PPE: coveralls over long-sleeved shirt and long pants, chemical resistant gloves, footwear plus socks
Manufacturer: Regal Chemical Company EPA Reg. # 48234-10


Professor of Weed Science and Extension Specialist
Horticultural Science

Publication date: Feb. 27, 2015

Recommendations for the use of agricultural chemicals are included in this publication as a convenience to the reader. The use of brand names and any mention or listing of commercial products or services in this publication does not imply endorsement by NC State University or N.C. A&T State University nor discrimination against similar products or services not mentioned. Individuals who use agricultural chemicals are responsible for ensuring that the intended use complies with current regulations and conforms to the product label. Be sure to obtain current information about usage regulations and examine a current product label before applying any chemical. For assistance, contact your local N.C. Cooperative Extension county center.

N.C. Cooperative Extension prohibits discrimination and harassment regardless of age, color, disability, family and marital status, gender identity, national origin, political beliefs, race, religion, sex (including pregnancy), sexual orientation and veteran status.