Aerial spraying of pampas grass in difficult conservation sites.
Pampas grass (Cortaderia selloana) has invaded many coastal cliff, dune and swamp communities throughout New Zealand, displacing native species. Control of pampas grass in some of these places can be challenging. Three different devices for spraying herbicide from a helicopter were tested: a beer keg spot sprayer, a weighted nozzle, and a directed lance. Their relative cost and effectiveness were assessed at Pouto Swamp, Northland; 40 plots were assessed prior to, at 3 months, and at 12 months after spraying with haloxyfop. The pampas grass clumps defined the sampling points within the plot (10 adjacent pampas plants per plot). The relative efficiency of the three devices in spraying three large blocks of pampas grass was also measured. All three devices gave effective control of pampas grass with minimal non-target damage. The keg was the cheapest because it used the least herbicide mixture and could be used with a smaller and cheaper helicopter. The original experimental design was not followed in its entirety so some variables were confounded. Most treated plots were showing regrowth 12 months after treatment, and follow-up treatment would be needed to effect complete control of the infestation.