Increasing foliar herbicide options for controlling Clidemia hirta (L.) D. Don

Clidemia hirta (L.) D.Don. (Koster’s curse) is a highly invasive, tropical understory shrub that was discovered in north Queensland in 2001. It was an eradication target species at a single location until the discovery of a second infestation in July 2015. The eradication program mostly involved manually uprooting entire plants; however the discovery of the second infestation signalled a need for more control options to accompany changes in managing this weed by a broader range of stakeholders. The second infestation provided sufficient plants to test eight high-volume foliar herbicides at one or two rates. Three of these herbicides were also applied using a low-volume foliar spraying technique, and comparisons were made of the effectiveness, volume and amounts of active ingredients applied using high and low-volume methods. Herbicide damage was assessed one, three and seven months after treatment. High and low-volume rates of treatments containing 600 g L−1 of triclopyr, 333 g L−1 fluroxypyr, and 300 g L−1 triclopyr + 8 g L−1 aminopyralid + 100 g L−1 picloram were effective. Treatments with 600 g kg−1 metsulfuron-methyl, 300 g kg−1 metsulfuron-methyl + 375 g kg−1 of aminopyralid and 140 g L−1 fluroxypyr +10 g L−1 aminopyralid was also effective at both high volume rates tested. Treatment with 625 g L−1 of 2,4-D amine was less effective, and results for treatments with 360 g L−1 of glyphosate were more variable, than the preceding treatments. This trial identified several effective active ingredients to assist in managing a broader C. hirta incursion