NC State Extension Publications


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Trade Name: Ronstar Common Name: oxadiazon Formulations: 2G, 3.17FL

Preemergence control of annual grasses and broadleaf weeds in field and container-grown woody ornamentals, landscapes, and turf (excluding home lawns). Also used in conifer nurseries. Does not inhibit root growth; thus Ronstar is often used in newly potted woody nursery crops.

Amount of Active Ingredient Amount by Formulation
2G 3.17FL
Per Acre 2 to 3 (or 4)* lb 100 to 200 lb 80 to 122 fl oz
Per 1,000 sq ft 2.25 to 4.5 lb 1.85 to 2.8 fl oz
* maximum single dose for the FL formulation is 3 lb ai/A, but 4 lbai/A for the GR formulation. Apply no more than 8 lb ai/A per year.

Major Weeds Controlled

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Goosegrass, crabgrass, other annual grasses, woodsorrel, bittercress, phyllanthus, willowherb, and many other annual broadleaves.

Major Weeds Not Controlled

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Chickweed, pearlwort and eclipta are not controlled. Only partial control of galinsoga and spurge should be expected. Emerged weeds are not controlled by the GR formulation but the FL formulation has some postemergence activity.

For Best Results

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Irrigate immediately after application. Do not disturb the soil surface by cultivation after treatment. May be applied to newly transplanted and established ornamentals.

Cautions and Precautions

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Do not incorporate. Do not apply the granular formulation to wet foliage or under conditions in which granules will collect on leaves. Do not use on plants that will bear edible fruit within one year. The following plants have been found to be sensitive under some growing conditions: andromeda, azalea, cotoneaster, spring heath, Canadian hemlock, hibiscus, rhododendron, Norway and white spruce, and viburnum. Do not use the FL formulation on cool-season turf. Directed applications to nursery stock are suggested to avoid injury. Do not apply in greenhouses.

Residual Activity

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Residual control may be expected to last three to four months in field soil, less in containers. In field sites, residual effects on grass cover crops have been observed five months after treatment. In container nurseries, residual activity will be less than 60 days in summer months.

Volatility and Leaching Potential

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Moderately volatile. Irrigate immediately after application. Very low water solubility and adsorption to organic matter prevent leaching.

Symptoms and Mode of Action

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Contact action by affecting the young shoot as it grows through the treated zone. Symptoms of injury generally consist of areas of necrotic tissues where the granules have adhered to the foliage or foliage is contacted by spray applications. WSSA – 14; HRAC group E

Additional Information

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Worker Protection Standards REI: 12 hours
PPE: applicators must wear long-sleeved shirt, long pants, chemical-resistant gloves, socks and shoes, and eye protection
Manufacturer: Bayer EPA Reg. # 432-866 (2G); # 432-1465 (3.17FL)


Professor of Weed Science, Extension Specialist & Department Extension Leader
Horticultural Science

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Publication date: May 22, 2019
Revised: May 23, 2019

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