Control of Invasive Weeds in Rangelands and Natural Areas in Hawai'i

Philip Motooka
Statewide Project

Weed ID and control workshop

Objective 1. Prepare CD references and lessons for extension agents.

In order to help extension staff identify weeds, photographs of nearly 200 species have been scanned onto CD’s and distributed to livestock agents. This is the first “draft”. It is anticipated that in a year, a revised, higher resolution version will be made and distributed to agents. Work has been initiated on PowerPoint presentations on weed science principles that will be used by agents in future training workshops.

Objective 2. Determine if the adjuvants such as LI-700, Silwet L-77, crop oil and Nu-Film will significantly increase the efficacy of MCPA on Senecio madagascariensis, of dicamba on Rhodomyrtus tomentosa and on Senna spp.

Objective 3. Establish the susceptibility of woody species to VLVBB applications of triclopyr.

Accomplishments: A very-low-volume basal bark (VLVBB) application trial was initiated on Acacia mearnsii on Kauai. Also a very-low-volume foliar application (VLV) trial on Eucalyptus spp. saplings was installed also on Kauai. Both these trials were in cooperation with the Division of Forestry and Wildlife (DOFAW). A trial on foliar applications of dicamba DGA to control Rhodomyrtus tomentosa, an invasive weed tolerant to most available herbicides was installed on Kauai in cooperation with DOFAW and a rancher. Results of these trials are pending. Project personnel provide consultation to two large ranches on Maui on large scale weed suppression operations. In the first, aerial applications were made on 500 acres of Ulex europaeus infested pastures. It is anticipated that several thousands of dollars will be saved over their old ground application program which was not stopping the advance of U. europaeus. In the second, an aerial application program was prescribed to control mixed brush species on 500 acres. These invasive species were Psidium guajava, Ardesia humilis, Schinus terebinthifolius, and Miconia calvescens. This latter project involves participation of the National Park Service and DOFAW. Results of these operations are pending.

Outcomes: Research has been initiated and results are pending. It is anticipated that methodology developed will be adopted by ranchers, foresters and others. These methods will be efficient, effective and environmentally safe.