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ARS Home » Pacific West Area » Albany, California » Western Regional Research Center » Invasive Species and Pollinator Health » Research » Publications at this Location » Publication #314327
Title: Evaluation of six herbicides for control of swamp smartweed [Persicaria hydropiperoides (Michx.) Small] under flooded and moist soil conditions

Author
item Madsen, John
item WERSAL, RYAN - Lonza Corporation

Submitted to: Journal of Aquatic Plant Management
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/24/2015
Publication Date: 7/1/2015
Citation: Madsen, J.D., Wersal, R.M. 2015. Evaluation of six herbicides for control of swamp smartweed [Persicaria hydropiperoides (Michx.) Small] under flooded and moist soil conditions. Journal of Aquatic Plant Management. 53:224-227.

Interpretive Summary: Six herbicides (2,4-D, diquat, glyphosate, imazamox, imazapyr, and triclopyr) were tested for efficacy on swamp smartweed (Polygonum hydropiperoides Michx.) in two studies in Mississippi. In the first study, glyphosate, imazapyr, and triclopyr were tested at the maximum and one-half the maximum allowable label rate. A nonionic surfactant was added to reach treatment. In the second study, 2,4-D, diquat, glyphosate, imazamox, imazapyr, and triclopyr were tested at the maximum and one-half the maximum allowable label rate. A nonionic surfactant was added to reach treatment. Our results indicated that 2,4-D, glyphosate, imazamox, imazapyr, and triclopyr would provide suitable control in the year of treatment, but the selection of these herbicides operationally depends on the use restrictions of the water and the desirability of selective control, as well as cost and local regulations.

Technical Abstract: Six herbicides (2,4-D, diquat, glyphosate, imazamox, imazapyr, and triclopyr) were tested for efficacy on swamp smartweed (Polygonum hydropiperoides Michx.) in two studies in Mississippi. In the first study in a pond, glyphosate (2.1 and 4.2 kg ai ha-1), imazapyr (0.3 and 0.5 kg ai ha-1), and triclopyr (3.4 and 6.7 kg ai ha-1) treatments were tested in 1 m2 plots, with each herbicide rate and an untreated reference replicated three times. A non-ionic surfactant was added at 0.25% v/v to each herbicide rate. Herbicides were applied to a carrier volume of 247 L ha-1. Plots were monitored weekly for five weeks after treatment, with percent control estimated visually to the nearest 10%. In the second study, a moist soil wetland was used for testing six herbicides. This study used two rates of 2,4-D (2.1 and 4.2 kg ae ha-1), diquat (2.2 and 4.5 kg ai ha-1), glyphosate (2.1 and 4.2 kg ae ha-1), imazamox (0.6 and 1.1 kg ai ha-1), imazapyr (0.2 and 0.5 kg ai ha-1), and triclopyr (3.4 and 6.7 kg ae ha-1) and an untreated reference. Plots were 1 m2 in area, and all treatments replicated four times. As before, a non-ionic surfactant was added at 0.25% v/v to each spray solution. The herbicides were applied using a low volume 7.5 L backpack sprayer calibrated to 247 L ha-1 (26 GPA). Efficacy was monitored visually for six weeks after treatment (WAT). In the first study, both the low and high rates of glyphosate (92 and 97%) and imazapyr (98 and 93%) exceeded 90% control by 5 WAT. In the second study, only diquat did not achieve 90% control by 6 WAT. Therefore, we found that 2,4-D, glyphosate, imazamox, imazapyr and triclopyr would all provide suitable control, but selection of a particular herbicide depends on the desire for selective control and the potential uses of the water.