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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 #365685

Research Project: Enhancing Water Resources Stewardship through Aquatic and Riparian Weed Management

Location: Invasive Species and Pollinator Health

Title: Torpedograss control via submersed applications of systemic and contact herbicides in mesocosms

item TURNAGE, GRAY - Mississippi State University
item WERSAL, RYAN - Minnesota State University
item Madsen, John

Submitted to: Journal of Aquatic Plant Management
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/26/2019
Publication Date: N/A
Citation: N/A

Interpretive Summary: Torpedograss is a widespread nuisance-forming invasive plant to a variety of aquatic systems, including ditches and wetlands. While many have used foliar-applied herbicides to control infestations, no published reports are available on submersed injection of herbicides into waters to control torpedograss. Nine aquatic herbicides were tested with submersed injection. While none of the herbicides showed significant reductions in biomass at eight weeks after treatment (WAT), by 52 WAT penoxsulam, topramezone, flumioxazin, and carfentrazone-ethyl reduced root or shoot biomass.

Technical Abstract: Torpedograss (Panicum repens) is a perennial invasive aquatic plant species that is spreading across the southeastern US. Torpedogass can survive in terrestrial and aquatic environments rooted to hydrosoil or form large floating islands (tussocks) that can limit human and wildlife uses of waterbodies. Portions of tussocks can break off, float away, and start new torpedograss infestations in other locations thereby making the problem worse. Limited data exists concerning submersed chemical control methods that are effective at controlling torpedograss. This work was conducted to investigate short- and long-term submersed chemical control options of torpedograss grown in outdoor mesocosms. Nine herbicides labeled for use in aquatic environments and a non-treated reference were evaluated. Eight weeks after treatment (WAT), harvested plants were separated into root/rhizome and shoot/leaf tissues, placed in labeled paper bags, dried in a forced air oven for five days at 70C, then weighed. None of the herbicides significantly reduced root/rhizome tissues for torpedograss eight WAT, however penoxsulam (0.025 ppm), topramezone (0.05 ppm), flumioxazin (0.4 ppm), and carfentrazone-ethyl (0.2 ppm) had reduced root/rhizome tissue by 52 WAT. Triclopyr (1.5 ppm), diquat (0.37 ppm), flumioxazin, and carfentrazone-ethyl had reduced shoot/leaf tissue at eight WAT. At 52 WAT, penoxsulam, topramezone, flumioxazin, and carfentrazone-ethyl had reduced shoot/leaf tissues. Based on these findings, additional research needs to be conducted to determine if long term torpedograss control can be claimed on these herbicide labels.