Developing an effective glyphosate application technique to control Bischofia javanica Blume, an invasive alien tree species in the Ogasawara Islands

Abstract

Bischofia javanica is a non-native tree species in Japan's Ogasawara Islands, where it threatens native tree species due to its rapid propagation and growth. An effective method is needed to limit the expansion of B. javanica populations and to conserve the natural forest ecosystem of the islands. For this purpose, we examined the effectiveness of a new application technique for the herbicide glyphosate on B. javanica. In this method, glyphosate solution is directly injected into holes drilled in the stem, and each hole is then plugged with a cork stopper to prevent loss of the solution, namely the drill-and-plug method. We also developed an allometric regression model linking stem diameter with total aboveground biomass (AGB) to estimate the necessary herbicide dosage. Our results suggest that between 0.1 and 0.5 g kg⁻¹ (active ingredient per unit AGB) is required to control most B. javanica trees. Verification of the drill-and-plug method using the minimum dosage (0.1 g kg⁻¹) showed that most of the herbicide-treated trees were killed. These results suggest that the drill-and-plug method can help control the B. javanica invasion of the Ogasawara Islands.

Keywords:

• Bischofia javanica
• Glyphosate
• Herbicide
• Invasive species
• Ogasawara (Bonin) Islands

Acknowledgments

We are grateful to H. Utsugi, H. Sakai, K. Miyamoto, T. Otani, M. Noguchi, and other members of the Forestry and Forest Products Research Institute for their helpful comments on an early version of the manuscript. We thank T. Yasui and the members of the Ogasawara Wildlife Research Society for their assistance with our field measurements of tree biomass; Y. Hoshi and H. Umeno, residents of the Ogasawara Islands, for their help with the verification tests; and N. Yamashita, S. Makino, and I. Okochi, as well as other members of Forestry and Forest Products Research Institute, for their support during the study. We also thank the members of the Kanto Regional Forest Office at Ogasawara for maintaining the Coffee-yama test site. The authors would like to thank the coordinating editor and two anonymous reviewers for their valuable comments and suggestions to improve the manuscript. The verification experiment was carried out as a part of a research project funded by the Japan Forest Technology Association and the Japan Ministry of the Environment.

Notes

Electronic supplementary material The online version of this article (doi:10.1007/s10310-014-0457-y) contains supplementary material, which is available to authorized users.