Evaluation of pre-emergence herbicides contained within a hydromulch cap to determine weed control and safety for two native Hawaiian grasses in a simulated roadside environment

Abstract

As a result of Federal Department of Transportation initiatives for native roadside planting mandates, many states are increasing native plant utilization on roadsides. Although efforts to use native Hawaiian plants were initiated as early as the mid 1990s, it was not until 2006 that studies for developing species-specific roadside establishment protocols were conducted (Baldos, DeFrank and Sakamoto 2010). Many native Hawaiian plants such as Myoporum, Dodonaea, Vitex, Sida, Scaevola, and Sapindus have a broad range of elevation adaptation. Thus they can be grown in coastal, inland, and upland Hawaiian conditions (Bornhorst 1994). Native species with a wide range of location adaptability represent roadside re-vegetation candidates with a high potential for successful establishment and long term persistence. The native grass Sporobolus virginicus (Akiaki grass), has been planted on Maui along the Mokulele highway corridor. In this project S. virginicus transplanted plugs took an unusual 3 years to establish because of the lack of information on roadside establishment and difficulties in weed control and irrigation (Baldos et al. 2010). The cost of establishing S. virginicus was estimated at $142,600 per hectare compared to traditional Bermudagrass (Cynodon dactylon) which costs only $87,700 (Baldos et al. 2010). The Mokulele planting exemplifies the need for well developed roadside native planting establishment protocols, which incorporate techniques for large scale plantings and weed control. In this thesis, herbicides will be characterized for safety and effectiveness during the establishment of native Hawaiian species identified as candidates for road-side plantings.