Herbicidal control of selected alien plant species in Hawaii Volcanoes National Park: a preliminary report

Abstract

Herbicide tests were conducted between April 1984 and June 1986 on 7 species of alien plants which have been classified as current or potential threats to native ecosystems within Hawaii Volcanoes National Park. The study was designed to be an initial series of tests to develop effective treatment techniques and to gather some baseline information on the effects of herbicides on native flora. Highly effective treatments were found for Russian olive (Linociera lisustrina) (TORDON RTU on cut stumps) and for both species of silky oak (Grevillea banksii and g. robusta) (2.5% GARLON 4 in diesel oil applied in continuous frill cuts). No hazards to native plants were detected. Treatments for glorybush (Tibouchina urvilleana) (20% GARLON 4 in diesel oil on cut stumps) and yellow Himalayan raspberry (Rubus ellipticus) (40% GARLON 4 in a foliar drizzle spray and 20% TORDON 22K in water on cut stumps) appeared effective: however, further testing is necessary to refine treatments, verify results, and further assess potential harm to native plant species. Kahili ginger (Hedychium sardnerianum) was effectively controlled with TORDON 1OX pellets; however, further testing is warranted for several reasons. A 2% foliar spray of ROUNDUP in water was not completely effective on blackberry (Rubus arsutus), but it did provide a good measure of control and would be useful in selected situations. Further testing on blackberry is necessary to increase treatment effectiveness and to evaluate other treatments. We recommend continued modest emphasis on herbicide research in Hawai'i's native ecosystems to: increase treatment effectiveness on these and other problem plants: evaluate the effects of retreatment regimes: increase knowledge of hazards to native plants and animals: broaden the range of safe chemical tools needed to integrate herbicides with other methods of ecosystem restoration: monitor operational herbicide programs for efficacy and cost effectiveness: increase long-term monitoring of treatment effects in selected areas; and determine and enhance responsible management programs in near-native ecosystems.