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Trade Name: Biathlon Common Name: oxyfluorfen + prodiamine Formulation: 2.75G (2+0.75)

Preemergence control of grasses and broadleaf weeds in container- and field- grown woody ornamentals. Not recommended for use in landscape plantings.

Amount of Active Ingredient Amount by Formulation
Per Acre 2.75 (2+0.75) lb 100 lbs
Per 1,000 sq. ft. 2.3 lbs

Major Weeds Controlled

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Several annual grasses and broadleaf weeds including large crabgrass, bittercress, groundsel, oxalis, dogfennel, phyllanthus, cudweed, and prickly lettuce.

Major Weeds Not Controlled

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Eclipta, doveweed, perennial weeds and emerged weeds. Note: variable results on spotted spurge have been reported.

For Best Results

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Do not incorporate physically. Irrigate immediately after application to activate the herbicide. Repeat application at two to three month intervals. Do not apply more than twice a year. Remove existing weeds before application.

Cautions and Precautions

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Apply to dry foliage only. Even labeled ornamental species may be injured by Biathlon if granules adhere to the foliage. If granules adhere to foliage it is important to remove them before irrigation. Shake plants or hand water immediately to wash the particles off the plant foliage. Do not apply to plants such as daylily, liriope, yucca, or Hosta with leaves that channel granules to the leaf base. Do not use in greenhouses. Not recommended for bedding plants, liner production beds, herbaceous groundcovers, flowers, turf, or plants bearing edible fruit.

Residual Activity

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In container nurseries, six to twelve weeks of weed control can be expected, depending on weed species, substrate, temperature, and irrigation practices. Bittercress control has been observed for 10 to 12 weeks but other species are typically controlled for 8 weeks or less.

Volatility and Leaching Potential

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Low volatility and low leaching potential. However, do not apply in enclosed structures as volatilization is possible. In container nurseries, surface runoff may result when broadcast applications are employed since many granules fall between pots. Otherwise, the potential for leaching and surface runoff is low.

Symptoms and Mode of Action

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Oxyfluorfen acts as a contact herbicide, disrupting cell membranes via a mechanism that requires light for activation. Prodiamine inhibits root development by affecting cell division. See the factsheets for Goal and Barricade for more details. Injury symptoms on ornamentals include contact-type burn where granules are trapped on the foliage and girdling at the soil line on some azalea cultivars. Oxyfluorfen: HRAC Group E; WSSA Group 14. Prodiamine: HRAC Group K1; WSSA Group 3.

Additional Information

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Worker Protection Standards REI: 24 hours
PPE: coveralls over long-sleeved shirt and long pants, chemical resistant footwear plus socks, chemical resistant gloves
Manufacturer: OHP EPA Reg. # 59807-12


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

Publication date: Aug. 24, 2016

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