Developing additional herbicide control options for rubber vine (Cryptostegia grandiflora R. Br.)

Abstract

Herbicide control of rubber vine (Cryptostegia grandiflora R.Br.), a Weed of National Significance in Australia, can be effectively achieved in most situations using a range of chemicals and various techniques, including basal bark, cut stump, foliar and aerial applications. Nevertheless control in areas with poor access and with native vegetation still poses difficulties for some land managers, particularly doing so in a cost effective manner.
The successful incorporation of low-volume high-concentration herbicide applications into control programs for several woody weeds in recent years prompted further testing of this technique for control of rubber vine. The efficacy of single rates of four herbicides plus a combination of two herbicides was compared against an untreated control. The herbicide treatments tested contained the active ingredients aminopyralid/ metsulfuron-methyl (375/300 g a.i. kg−1), metsulfuron-methyl (600 g a.i. kg−1), metsulfuronmethyl + glyphosate (600 + 360 g a.i. kg−1), triclopyr/ picloram (300/100 g a.i. kg−1) and triclopyr/picloram/ aminopyralid (200/100/25 g a.i. kg−1).
Two years after application, triclopyr/picloram was the only treatment to have given 100% mortality, but statistically it was not significantly different (P >0.05) to aminopyralid/metsulfuron-methyl, metsulfuronmethyl or triclopyr/picloram/aminopyralid, which averaged between 82–91% mortality. The metsulfuronmethyl + glyphosate treatment performed poorly (49% mortality): this appears to be associated with some antagonistic effect given that metsulfuron-methyl on its own performed much better. Based on these results, two more trials have been initiated to refine rates for metsulfuron-methyl and triclopyr/picloram and to compare low-volume high-concentration applications against traditional foliar spraying using the same herbicide (triclopyr/picloram) (in terms of efficacy and cost).