Proceedings of the Sixty-first Annual Meeting of the Northeastern ...

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EFFICACY OF GLYPHOSATE, IMAZAPYR AND TRICLOPYR FOR PHRAGMITES
MANAGEMENT IN A CONNECTICUT MARSH. T.L. Mervosh, Connecticut Agricultural
Experiment Station, Windsor; and D.P. Roach, All Habitat Services LLC, Madison, CT.
ABSTRACT
Common reed or phragmites (Phragmites australis (Cav.) Trin.) is an invasive
grass that dominates many wetland areas, including freshwater and brackish marshes
throughout the Northeast. This extremely tall, rhizomatous perennial displaces cattails
(Typha spp.) and other native plants. The efficacy of three herbicides was evaluated in a
study in a tidal marsh along the lower Connecticut River in Old Saybrook. The area was
mowed in March 2005 to cut down dry standing stalks of Phragmites. Plots were
arranged in a RCB design with three replicates per treatment. Plot dimensions were 20 ft
x 20 ft, and untreated alleyways (10 ft) surrounded each plot.
Herbicide products with aquatic use registrations were evaluated. Isopropylamine
salt of glyphosate, isopropylamine salt of imazapyr, and/or triethylamine salt of triclopyr
were sprayed over the top of Phragmites-dominated plots at one of three timings in 2005:
June 2 (‘A’), June 24 (‘B’), or September 14 (‘C’). Herbicide treatments were prepared in
2-L bottles. Based on calibration tests before each application, bottles were filled with
CO 2 to a specific pressure. For the ‘A’ timing, Phragmites was an average of 4 ft tall, and
herbicides were applied using a hand-held, four-nozzle spray boom with TeeJet 8003VS
tips. Spray volume was 25 gallons/A. For the ‘B’ and ‘C’ timings, Phragmites was an
average of 8 ft and 11 ft tall, respectively. Herbicides were applied from an elevated
platform mounted on an amphibious all-terrain vehicle driven in the alleyways.
Treatments were sprayed with a Hypro XT-043 boomless nozzle in two passes from
opposite ends of each plot. Spray volume was 50 gallons/A.
In addition to an untreated check, the following treatments were applied at all
three application timings: triclopyr at 1.5, 2.25 or 3 lb ai/A; glyphosate at 2 lb ai/A;
glyphosate + triclopyr (1 + 1.5 lb ai/A, or 2 + 0.75 lb ai/A); imazapyr at 0.5 lb ai/A;
imazapyr + triclopyr (0.125 + 1.5 lb ai/A, or 0.125 + 2.25 lb ai/A). For the ‘A’ and ‘B’
timings, two additional treatments were included in which triclopyr at 1.5 or 2.25 lb ai/A
was applied a second time to the same plots on September 9, 2005. All treatments
included a non-ionic surfactant (1 qt/A) in the spray solution.
Plots were evaluated periodically through September 2006 for height, relative
number of stems, vigor, injury symptoms, and effects on other plants. Most treatments
were more effective when applied in September 2005 (‘C’) than when applied in June
2005 (‘A’ or ‘B’). Treatments containing glyphosate and/or imazapyr were better than
treatments containing only triclopyr at reducing growth in 2006. Although triclopyr
suppressed Phragmites following 2005 applications, Phragmites growth the next year was
reduced substantially only when glyphosate or imazapyr was combined with triclopyr.
The imazapyr (0.5 lb ai/A) treatment and those containing glyphosate at 2 lb ai/A provided
the best control of Phragmites in 2006. Plots will be evaluated in 2007 for Phragmites
and for other plant species that emerge.
Triclopyr did not perform as well in this experiment as it has in large-scale
Phragmites management projects conducted by D. Roach. Application parameters such
as timing, spray volume and coverage are factors that likely influence triclopyr efficacy.
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