Outrunning the invasive species treadmill: Integrating biological control and other management techniques to restore invaded sites

Authors: Lake, Ellen; HOUGH-GOLDSTEIN, JUDITH - University Of Delaware

Submitted to: USDA Interagency Forum on Invasive Species
Publication Type: Proceedings
Publication Acceptance Date: 2/24/2017
Publication Date: 11/1/2017
Citation: Lake, E.C., and Hough-Goldstein, J.A. Outrunning the invasive species treadmill: integrating biological control and other management techniques to restore invaded sites. In: McManus, K.A., and Poland, T.M., (comps.) XXVII (28th) USDA Interagency Research Forum on Invasive Species. January 10-13; Annapolis, MD. FHTET-2017-06. Morgantown, WV: U.S. Department of Agriculture, Forest Service, Forest Health Technology Enterprise Team. 81 pages.

Interpretive Summary: Natural area managers often implement weed biological control programs with the goal of restoring native plant communities and/or ecosystem services to a pre-invasion level. In some cases, biological control alone may achieve this objective; however, in other sites integration of biological control with additional management techniques is necessary. Control of one invasive weed can lead to increases in the population of another weed, the invasive treadmill effect. Biological control has been successfully integrated with herbicides, mechanical control, fire, grazing and other management techniques to manage invasive weeds and prevent the invasive treadmill effect. Mile-a-minute weed, Persicaria perfoliata (L.) H. Gross, is an aggressive annual vine that has invaded the eastern United States. In some cases, successful biological control of mile-a-minute weed by the weevil Rhinoncomimus latipes Korotyaev has resulted in replacement by other undesirable vegetation. Two small-scale field experiments in this system successfully integrated biological control with native plantings to restore plant communities. In one experiment, biological control was combined with plantings of a native seed mix that included native warm and cool season grasses and forbs. Native plant richness and diversity increased after three years in the integrated plots. In a second experiment, weevil releases were integrated with a single application of a pre-emergent herbicide and plantings of a native forb and tree. Mile-a-minute seedling counts were significantly higher in the no-herbicide plots in 2009, as well as 2010 and 2011, a legacy of the one-time treatment in 2009. Two years later, the cover of native plants in the integrated treatment plots was greater than 80%. Six years post-treatment, two sites would benefit from additional management, while a third site had minimal invasive weed problems. Sites will vary, and management strategies must be customized accordingly. In both experiments, the integration of techniques reduced the abundance of the target weed, promoted recruitment of additional native plant species that were not included in the plantings, and at least temporarily prevented dominance by other invasive plants compared to non-planted control plots.

Technical Abstract: The goal of many weed biological control programs in natural areas is to restore native plant communities and/or ecosystem services to a pre-invasion level. In some cases, biological control alone may achieve this objective; however, in others integration of biological control with additional management techniques is necessary. Successful control of one weed species may result in replacement by another, the invasive treadmill effect. Integrating biological control with herbicides, mechanical control, fire, grazing or other techniques to manage invasive weeds may successfully control the target weed and prevent the invasive treadmill effect. Mile-a-minute weed [Persicaria perfoliata (L.) H. Gross] is an aggressive annual vine that has invaded the eastern United States. Successful biological control of mile-a-minute weed by the weevil Rhinoncomimus latipes Korotyaev has led to replacement by other invasive weeds in some sites. Biological control was successfully integrated with native plantings in two small-scale field experiments in this system to restore plant communities. One experiment combined biological control with plantings of a native seed mix that included warm and cool season grasses and an annual and a perennial forb. Native plant richness and diversity increased in these plots after three years. The second experiment integrated weevil releases with a single application of a pre-emergent herbicide and plantings of a native forb and tree. Mile-a-minute seedling counts were significantly higher in the no-herbicide plots in 2009, as well as 2010 and 2011, a legacy of the one-time treatment in 2009. After two years, the cover of native plants in the integrated treatment plots was greater than 80%. In 2015, the number of mile-a-minute seedlings no longer differed between the herbicide and no-herbicide plots and were very low across all treatments. Six years post-treatment one site does not need additional management, mile-a-minute cover has increased at a second site, and one of the replacement weeds, Japanese stiltgrass [Microstegium vimineum (Trin.) A. Camus] has increased at a third site. In both experiments, the integration of management techniques reduced the abundance of the target weed, promoted recruitment of additional native plant species that were not included in the plantings, and at least temporarily prevented dominance by other invasive plants compared to non-planted control plots. Sites will vary, and customized and adaptive management strategies will be required.