Emergent Weeds in Marshes

2,4-D (Hardball)

Rate 2.3 gal/A in minimum spray volume of 5 gal mix/A with surface applications; 2.3 gal/A through standard boom system with minimum of 5 gal/A of spray mix.

Time Apply in spring or early summer; if needed, a second treatment may be applied before September.

Remarks Applications should be made when leaves are fully developed, above the waterline, and actively growing. Do not apply when wind speeds are at or above 10 mph (ground/surface applications) or 5 mph (aerial applications). No use-restrictions for swimming, fishing, watering livestock or domestic purposes other than noted below. See label for instructions on use of drift control agents and equipment to prevent drift to sensitive crops.

Caution Limited to 2 applications per season; maximum of 2.3 gal/A (4 lb ae/A) per application; minimum 21 days between applications. Irrigation/spray use of water requires setback distance of ≥ 600 ft from functional water intakes, waiting period of 7 days or approved assay of 2,4-D concentrations <100 ppb. Drinking water use requires setback distance from functioning water intakes ≥600 ft or drinking water notification prior to application. See label for sampling requirements and posting requirements.

Site of action Group 4: synthetic auxin

Chemical family Phenoxy acetic acid

2,4-D dimethylamine salt (DMA 4 IVM, Base Camp and others)

Rate 2 to 4 pints/A.

Time Apply in spring or early summer when aquatic weeds appear.

Remarks Repeat as necessary to kill regrowth or missed plants; use 4 pints/A rate when plants are mature or dense.

Caution Maximum of 8 pints/A per application; limited to 2 applications per season. Toxic to fish and aquatic invertebrates. Do not treat areas free of weeds. If weeds are abundant, consider partial treatments to avoid fish kill (due to low oxygen from decomposing weeds). Do not use water for irrigation if approved assay indicates 2,4-D concentration is above 0.1 ppm (100 ppb). Do not use treated water for drinking if approved assay indicates 2,4-D concentration is above 0.07 ppm (70 ppb). See label for sampling requirements and posting requirements.

Site of action Group 4: synthetic auxin

Chemical family Phenoxy acetic acid

glyphosate (Rodeo, AquaNeat, AquaPro, AquaMaster, Cinco, Accord Concentrate and others)

Rate 0.75 to 3.75 lb ae/A (1.5 to 7.5 quart/A) applied as a broadcast spray or 0.75 to 2.0% solution in water applied through hand-held or high-volume equipment.

Time Apply when weeds or brush are actively growing.

Remarks See product label for application rate and growth stage of weed and brush species. If water is in the area to be sprayed, add a surfactant labeled for use in water at the manufactures' surfactant label recommendations. Surfactant must be at least 80% ai. If used following drawdown, allow seven days after treatment before reintroducing water; treat within one day after drawdown to ensure weeds are actively growing.

Caution Rain within 6 hours after application may reduce effectiveness. Do not apply within 0.5 miles upstream of potable water intakes. Apply to moving bodies of water only while traveling upstream. Do not exceed 3.75 lb ae/A in any single application being made over water. Take care to avoid drift to desirable plants. Do not spray where weeds do not exist.

Site of action Group 9: inhibits EPSP synthase

Chemical family None generally accepted

imazamox (Clearcast)

Rate 0.125 to 0.5 lb ai/A (16 to 64 fl oz/A)

Time Apply as a foliage spray to actively growing emergent and floating plants.

Remarks Rate depends on species to be controlled. Postemergence applications require adding a spray adjuvant approved for use in aquatic sites. There are no restrictions on livestock watering, swimming, fishing, or domestic use as long as the setback restriction is observed, or for agricultural sprays.

Caution Do not use treated water to irrigate greenhouses, nurseries, or hydroponics. Do not use treated water for other irrigation purposes unless concentrations in water are equal to or less than 50 ppb. Note label restrictions on setback restrictions to potable water intakes.

Site of action Group 2: acetolactate synthase (ALS) inhibitor

Chemical family Imidazolinone

imazapyr, isopropylamine salt (Arsenal, Habitat, Polaris AQ)

Rate 0.5 to 1.5 lb ae/A (2 to 6 pints/A), applied with surface or helicopter equipment in minimum of 2 gal water/A. For low volume foliar applications, use 0.5 to 5% concentration (without applying more than 6 pints/A per year).

Time Apply to vigorously growing emergent and floating vegetation.

Remarks Controls several annual, biennial, and perennial grass and broadleaf species. Rate depends on weed species and growth stage at time of application. Postemergence applications require adding a spray adjuvant (such as a nonionic surfactant or methylated seed oil) approved for use in aquatic sites. Controls emerged and floating vegetation that has most of its foliage above the water surface. No restrictions on recreational or livestock use of treated water. Moisten, but do not drench target vegetation.

Caution Do not apply more than 1.5 lb ae/A (6 pints/A product) per year. Do not apply within 0.5 miles of a potable water intake in a standing body of water unless the intake can be turned off for at least 48 hours after treatment. Do not apply to irrigation water. Unless imazapyr residues in the water are below 1 ppb, as determined by laboratory analysis, wait at least 120 days after application before using water for irrigation. To avoid oxygen depletion, treat no more than half a waterbody at a time, waiting 10 to 14 days between treatments. Do not spray where weeds do not exist.

Site of action Group 2: acetolactate synthase (ALS) inhibitor

Chemical family Imidazolinone

triclopyr (Renovate 3)

Rate 0.75 to 6 lb ae/A

Time Apply to actively growing broadleaf weeds and woody plants.

Remarks Use a labeled nonionic surfactant. Use the higher rates if hard-to-control species are prevalent or applications are in late summer or weeds are mature. There are no restrictions on recreation, including swimming and fishing, in treatment area or on livestock consumption of water.

Caution Do not apply when conditions favor drift to sensitive areas. Observe minimum setback distances from functional potable water intakes for human consumption. Do not exceed 6 lb ae/A per annual growing season.

Site of action Group 4: synthetic auxin

Chemical family Pyridine

penoxsulam (Galleon SC)

Rate 2 to 5.6 fl oz/A with at least 10 GPA for aerial foliar applications and up to 100 GPA for ground foliar applications; for pre- or postemergent applications to exposed sediments, use 5.6 to 11.2 fI oz/A in a total spray volume of 20 to 100 GPA.

Time Apply only to actively growing weeds.

Remarks For post emergent foliar applications or treatments to exposed sediments, use with a surfactant approved for aquatic use (use with organosilicone surfactants not recommended). May be mixed with other herbicides or algaecides according to label specifications. Single applications should target minimum effective concentration of 25 to 75 ppb; split or multiple applications should target an initial dose of 10 to 30 ppb and subsequent applications to maintain that concentration for a minimum of 60 days (use ELISA or other analytical techniques to determine penoxsulam concentrations).

Caution Maximum target concentration in any treated area is 150 ppb ai per annual growth cycle. Do not use in areas subject to rapid dilution, such as spot treatments in lakes or other large water bodies.

Site of action Group 2: acetolactate synthase (ALS) inhibitor

Chemical family Triazolopyrimidine