Status of biological control of the shrub gorse (Ulex europaeus) on the Island of Hawaii

Abstract

On the island of Hawaii, gorse (Ulex europaeus L.) is limited to an isolated core infestation of approximately 2000 hectares with scattered plants and small patches in the surrounding 10,000 hectares. Between 1985 and 2000, seven biological control agents were introduced, five of which successfully established. By 2000, their combined impact had reduced the yearly growth of new shoots by over 50%. In 2001/2002, the ranch leasing the area decided to solve the gorse problem with an area wide program of aerial spraying and burning that destroyed over 95% of the gorse in the core area. With no follow up treatment, within three years the gorse had regenerated and was as abundant as before the control program. The effect on the complex of biocontrol agents, however, was devastating. One agent disappeared; the distribution and relative abundance of the other four was permanently altered, and their combined impact now appears to be significantly less than before the control effort.

Citation

Markin, G. P.; Conant, P. 2013. Status of biological control of the shrub gorse (Ulex europaeus) on the Island of Hawaii. In: Wu, Yun; Johnson, Tracy; Sing, Sharlene; Raghu, S.; Wheeler, Greg; Pratt, Paul; Warner, Keith; Center, Ted; Goolsby, John; Reardon, Richard, eds. Proceedings of the XIII International Symposium on Biological Control of Weeds; September 11-16, 2011; Waikoloa, Hawaii, USA. Session 9: Post-release Evaluation and Management. Fort Collins, CO: U.S. Department of Agriculture, Forest Service, Forest Health Technology Enterprise Team. Online: http://www.invasive.org/proceedings/pdfs/Markin%20-%20Conant.pdf