Abstract

1. Use of Mechanical and Chemical Treatments To Control Invasive Plants at Sachuest Point National Wildlife Refuge in Rhode Island. Suzanne Hoover Paton1, Erin J. Riley2, and Sharon K. Ware1 1Rhode Island National Wildlife Refuge Complex, Charlestown RI, 21 Maxfield Court, Barrington, RI Abstract The control of non-native invasive plants is a primary management priority on National Wildlife Refuges. In southern New England, oriental bittersweet (Celastrus orbiculatus) and black knapweed (Centaurea nigra) are pervasive in coastal shrub and grassland habitats. In the mid-1990s, bittersweet dominated 80% of Sachuest Point National Wildlife Refuge (SPNWR; 242 acres) in Middletown, Rhode Island. An invasive control project was implemented in 2002 to control bittersweet and knapweed. Treatments included both mechanical and chemical applications, with timing of treatments based on research conducted by Connecticut College Arboretum at SPNWR during 2000-2001 and funded by the National Fish and Wildlife Foundation. We established 195 plots within 7 treatment fields to record changes in the number of bittersweet and knapweed stems. There was a significant reduction in the number of oriental bittersweet stems (p<0.05), and flowering black knapweed stems (p<0.05) from 2002-2004 on 15 treated acres. Although this project is ongoing, its initial success may provide information useful to land managers dealing with invasive plant infestations. Results Oriental Bittersweet: *A paired t-test for all fields combined showed a statistically significant reduction in the number of Oriental Bittersweet stems following the second year of treatment (2003-2004, p=0.007) and overall (2002-2004, p=0.017). The reduction in stems after only one year of treatment was not significant across fields (p=0.197). *Two of the three fields showed a significant reduction in the number of stems after one year of treatment. *All three fields showed a significant reduction in the number of stems between year 2 and year 3. Objectives Reduce the percent cover of invasive plants to levels that are manageable without the use of chemicals. Evaluate the effectiveness of mowing in early August, followed 30 days later by an herbicide application, to reduce the number of oriental bittersweet stems. Assess the effectiveness of mowing in mid-May, followed 30 days later by an herbicide application, to reduce the number of Black Knapweed stems. Black Knapweed: *A paired t-test for all fields combined showed a statistically significant reduction in the number of Black Knapweed stems between 2002-2003 (p=0.04), 2003-2004 (p=0.03), and overall following two years of treatment (2002-2004, p=0.005). *Three of the four fields showed a significant reduction in the number of stems after one year of treatment. *All four field showed a significant reduction in the number of stems between year 2 and year 3. Monitoring Methods *Vegetative response to treatments was monitored annually. *Monitoring procedures were modeled after those outlined in the Colorado Department of Agriculture’s ‘Creating an Integrated Weed Management Plan’(2000). *Each year, thirty plots were randomly selected within each of the 7 fields (the only exception was bittersweet field #3, which contained 15 plots because of its small size). *Each 1.4 m x 0.6 m (4.5 ft x 2 ft) plot was identified as having either more or less than ten stems of the respective invasive species. If the plot had less than ten stems, the exact number was recorded. *Knapweed fields were sampled in June of each year, with the number of flowering stems counted and recorded. *Bittersweet fields were sampled between late August and early September each year. *While different people conducted the surveys each year, all were trained and supervised by the Refuge staff in the use of this standard protocol. • Treatment Methods • A total of four Black Knapweed and three Oriental Bittersweet dominated fields were initially established for treatment in 2002. The fields ranged in size from 40x50 meters to 100x100 meters. • Oriental Bittersweet fields: • Hydro–axed during fall / winter. • Mowed in late July-early August each of the following years. Fields dominated by more than approximately 80% bittersweet cover were mowed with a brush hog mounted on a farm tractor (all fields during 2002-2003), while fields with less than 20% coverage were hand cut in bittersweet dominated areas only. • Approximately 30-40 days post mowing, all cut areas received an herbicide treatment. Mowed fields were broadcast sprayed using a boom sprayer and a 0.05% solution of Triclopyr (Garlon 4). Hand cut areas were treated with backpack sprayers. • Black Knapweed fields: • *Mowed in mid May each year. • *Sprayed with a 0.05% solution of Triclopyr (Garlon 4) approximately 30 days later using a boom sprayer. • NOTE: Knapweed fields did not receive a treatment in 2004 because they were scheduled to receive a burn treatment instead. The burn was not conducted due to weather, but is scheduled again for spring of 2005. Discussion Although significant reductions in invasive plants has been achieved in our initial 15 acre treated area, complete eradication of these plants on the refuge will require ongoing control efforts. We have currently expanded our treatment areas to a total of 35 acres. As invasive plants are eradicated in each field we will focus the restoration effort on planting native vegetation which can be maintained by prescribed fire and mechanical treatments. Acknowledgements National Fish and Wildlife Foundation Friends of the National Wildlife Refuges of Rhode Island Rhode Island Natural History Survey Rhode Island Wild Plant Society Connecticut College – Glen Dryer Norman Bird Sanctuary Connecticut River/Long Island Sound Ecosystem Team Norma Kline, Anne Wagner, Dana Robinson, Art McDonald, John Laauwe, Heather Baker, Seth Thompson, John Tucker and Andy Levesque, Ken Wagner