NC State Extension Publications


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Trade Name: Gemini Common Name: isoxaben + prodiamine Formulation: 0.65GR, 3.7 SC

Preemergence control of most annual broadleaf weeds and annual grasses in container or field grown nursery crops, landscape plantings, Christmas tree farms.

Gemini SC may also be used in turfgrass settings.

Amount of Active Ingredient Amount by Formulation*
3.7 SC (1.5 + 2.2 lb/Gal)
Per Acre 1.25 - 2.5 lb
(0.5 to 1.0 lb isoxaben + 0.75 to 1.5 lb prodiamine)
43.6 to 87 fl oz/A
Per 1,000 sq. ft. 1 to 2 oz
0.65 GR (0.25 + 0.4%)
Per Acre 0.65-1.3 lb
(0.25 to 0.5 lb isoxaben + 0.4 to 0.8 lb prodiamine)
100 to 200 lb
Per 1,000 sq. ft. 2.3 to 4.6 lb
*Note: do not exceed the equivalent of 1.5 lb ai/A of prodiamine per acre per year. This is equivalent to 375 lb of Gemini GR or 87 fl oz of Gemini 3.7SC per acre per year.

Major Weeds Controlled

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Broad spectrum control of annual broadleaf and grass weeds including bittercress, spurge, chickweed, henbit, groundsel, annual bluegrass, crabgrass, carpetweed, and many others.

Major Weeds Not Controlled

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Perennials and established weeds. Weak on eclipta, chamberbitter, phyllanthus, doveweed, morningglory and rice flat sedge. Does not control nutsedge.

For Best Results

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In field or landscape sites, apply in early spring or late summer before the emergence of target weeds, or immediately after cultivation. One-half inch or more of water is required for activation. In containers, hand weed before treatment and irrigate immediately after application. Apply Gemini GR to dry foliage and shake plants to remove granules from growing points. Gemini SC may be applied as an over the top spray on many species but directed applications are generally recommended.

Cautions and Precautions

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Do not apply to new transplants until soil has settled and there are no cracks. Do not apply to nursery seedbeds or transplant beds or to unrooted liners or cuttings. Do not use in enclosed structures. Do not apply to bedding plants or to areas where bedding plants will be planted within one year. Do not apply to pots less than 6 inches wide. Apply no more than 1.5 lb ai/A of prodiamine in a 12-month period. Use is prohibited on several species, check label for details.

Residual Activity

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Duration of weed control varies with application rate, management practices, and prevailing weather conditions. In cool climates or seasons, longer residual is expected than in warm climates or seasons. In containers, residual weed control rarely lasts more than 60 days in the southeastern U.S. Shorter residual is to be expected in mid-summer, longer residual in cooler weather.

Volatility and Leaching Potential

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Isoxaben is nonvolatile. Prodiamine is somewhat volatile and photolabile; therefore, the herbicide should be incorporated by irrigation or rainfall soon after application. Isoxaben leaches very little, and prodiamine is strongly adsorbed to soil so little leaching occurs.

Symptoms and Mode of Action

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Isoxaben inhibits cell wall biosynthesis and appears to disrupt root and hypocotyl development. Mode of action group: 29

Prodiamine affects root growth by inhibiting cell division. Mode of action group: 3

Additional Information

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Worker Protection Standards REI: 12 hours
PPE: coveralls, chemical resistant gloves, chemical resistant footwear plus socks
Distributor: ICI EPA Reg. # 58185-180 (GR), 53883-325-58185 (SC)


Professor of Weed Science, Extension Specialist & Department Extension Leader
Horticultural Science
Virginia Tech
Asst. Professor
University of Florida

Publication date: Feb. 20, 2018
Revised: June 21, 2023

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