Emergent Weeds along Irrigation Ditches

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

Rate 2 to 4 pints/A product in 20 to 100 gal water

Time Apply in spring or early summer when weeds appear, but prior to bud or bloom.

Remarks Repeat as necessary to kill regrowth or missed plants; use 4 pints/A rate when plants are mature or dense. Do not overspray to opposite bank or allow boom spray to be directed onto water surface; allow no more than 2 foot of overspray onto water, with an average of less than one foot.

Caution Maximum of 4 pints/A per application; limited to 2 applications per season, a minimum of 30 days apart. 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. Do not use on small canals with flow rates < 10 cfs where water will be used for drinking water purposes. Do not allow dairy animals to graze on treated areas for a minimum of seven days after application.

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 quarts/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 and brush are actively growing.

Remarks See 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 manufacturers' surfactant label recommendations. Surfactant must be at least 80% ai. In dry ditches or after drawdown, allow seven days after treatment before reintroducing water; treat within one day after drawdown to ensure weeds are actively growing. Apply as a 33% solution through wiper-type applicators. May be applied through hand-held or high-volume equipment as a 0.75 to 1.5% solution.

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 overlap bank side applications more than 1 foot into open water. Do not exceed 3.75 lb ae/A in a single application being made over water. Take care to avoid drift to desirable plants. With bankside applications, do not overlap more than one foot into open water. Do not spray where weeds do not exist.

Site of action Group 9: inhibits EPSP synthase

Chemical family None generally accepted

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 to canals or ditches unless a 120 day restriction on irrigation water can be observed or residual levels of imazapyr are determined by laboratory analysis to be less than 1.0 ppb. Do not apply to dry irrigation canals or ditches. Do not apply within 0.5 miles downstream of an active irrigation water intake. Applications upstream of active irrigation water intakes must be turned off for a period of time sufficient to allow treated water to completely flow past the intake (determined by water velocity, distance and length of water treated). 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