Red quinine tree has been recognized as a serious weed in the Galapagos National Park for three decades. During this time, a variety of control methods have been implemented, initially with poor results. In this article, we reviewed past efforts to control red quinine tree and tested a variety of herbicides and selective application methods. A mixture of picloram and metsulfuron (240 and 15 g ai/L, respectively) killed 73 to 100% of trees when applied to connecting machete cuts around the circumference of tree trunks (hack and squirt [HS]) at concentrations of 5, 10, and 20% in water, with larger trees requiring higher concentrations for best results. Although this herbicide mixture also was effective when applied using other methods, HS was the least labor intensive and costly. The control methods developed could be used to combat this weed in other locations including Hawaii and Tahiti.
Nomenclature: Metsulfuron; picloram; red quinine tree, Cinchona pubescens Vahl.
Additional index words: Cinchona succirubra, Galapagos National Park, Hawaii.
Abbreviations: BB, basal bark; CDRS, Charles Darwin Research Station; CS, cut stump; DBH, diameter at breast height; GNP, Galapagos National Park; GS, girdle and squirt; HS, hack and squirt; H, hack only; MASL, meters above sea level; WS, wide-band hack and squirt.