Sequential applications of diquat to control flowering rush (Butomus umbellatus L.)

Authors: TURNAGE, GRAY - Mississippi State University; BYRD, JOHN - Mississippi State University; WERSAL, RYAN - Lonza Corporation; Madsen, John

Submitted to: Journal of Aquatic Plant Management
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/18/2019
Publication Date: 7/1/2019
Citation: Turnage, G., Byrd, J.D., Wersal, R.M., Madsen, J.D. 2019. Sequential applications of diquat to control flowering rush (Butomus umbellatus L.). Journal of Aquatic Plant Management. 57:56-61.

Interpretive Summary: Previous work has demonstrated in the field that two diquat treatments during the summer growing season could effectively reduce rhizome bud density and production if performed over two or three years. This research was designed to determine if additional diquat treatments in a given season would be effective in reducing the time to controlling flowering rush rhizome buds. However, the research actually found that one treatment was as effective as four treatments in a given year at reducing rhizome bud density and production.

Technical Abstract: Butomus umbellatus (flowering rush) is an aggressive aquatic invasive plant species in the northern US and southern Canada. Flowering rush is capable of displacing many native aquatic/wetland plants which can disrupt ecosystem processes and affect human uses of waterbodies. Flowering rush has three growth forms: wetland plants along the margins of waterbodies, emergent plants in shallow waters (depth < 1.2 m), and fully submersed plants in deeper waters. Currently, operational control protocols utilizing two submersed applications of diquat (0.37 ppm) per growing season have achieved >80% control of the overall flowering rush tissues and propagule bank in the Detroit Lakes, MN system. However, at some local sites within the Detroit Lakes it has taken multiple years for this protocol to control flowering rush. In areas such as these a more aggressive control strategy may control flowering rush. This mesocosm study investigated sequential diquat applications every two weeks for flowering rush control. Plants were treated with diquat (0.37 ppm) once, two, three, or four times. All treatments reduced flowering rush tissues and propagules when compared to reference plants (p < 0.001). Additionally, all treatments reduced flowering rush at the same level of significance, thus there was no difference in any of the diquat treatments. This work suggests that a more aggressive treatment protocol than that already in use will not benefit resource managers, however these results need to be verified via field trials before resource managers alter existing treatment protocols that have been documented to control flowering rush.