Efficacy of combinations of diquat or triclopyr with fluridone for control of flowering rush

Authors: Madsen, John; TURNAGE, GRAY - Mississippi State University; GETSINGER, KURT - Us Army Corp Of Engineers (USACE)

Submitted to: Journal of Aquatic Plant Management
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/8/2016
Publication Date: 7/1/2016
Citation: Madsen, J.D., Turnage, G., Getsinger, K.D. 2016. Efficacy of combinations of diquat or triclopyr with fluridone for control of flowering rush. Journal of Aquatic Plant Management. 54(2):68-71.

Interpretive Summary: Flowering rush is a poorly-understood invasive aquatic plant that is spreading throughout the northern portion of the United States and southern Canada. To date, the only management technique that has proven effective on plants growing in permanent standing water is to use submersed treatments of diquat. While this is effective, not all sites are amenable to the use of diquat. We compared treatments of diquat, triclopyr, and fluridone alone, as well as combinations of either diquat or triclopyr followed by a fluridone treatment; in a tank study at Mississippi State University. We found that triclopyr was ineffective alone, and a preliminary treatment with triclopyr did not improve the effectiveness of fluridone. Fluridone alone and diquat alone were equally effective. We say no improvement in effectiveness when the fluridone treatment was preceded by a diquat treatment. If an adequate concentration and exposure time can be maintained, fluridone is also effective in controlling flowering rush.

Technical Abstract: Flowering rush (Butomus umbellatus L.) is an emerging invasive aquatic weed in the northern tier of the United States and southern Canada. While several management approaches have been tested, submersed treatment with diquat is the only use pattern substantiated with field efficacy data. We tested treatments of fluridone (30 µg L-1) with and without prior treatment with either diquat (0.19 mg L-1) or triclopyr (2 mg L-1), as well as diquat (0.19 mg L-1) or triclopyr (2 mg L-1) alone. Each treatment, and an untreated reference, was replicated in four 380 L tanks at an experimental mesocosm facility. After eight weeks, all treatments were harvested, and pots separated into above- and belowground biomass. The number of ramets and rhizome buds in each pot were also counted. Statistically, triclopyr was not effective in reducing above- or belowground biomass, or rhizome bud density. Both diquat and fluridone alone were effective in reducing above- and belowground biomass and rhizome bud density, with no statistical difference between them. Pre-treatment with diquat did not improve the efficacy of fluridone treatments. If an adequate exposure time to fluridone can be maintained, treatment with fluridone is as effective for management of flowering rush as submersed treatment with diquat.