Final Comprehensive Conservation Plan - U.S. Fish and Wildlife ...

Hakalau Forest National Wildlife Refuge
Comprehensive Conservation Plan
Kikuyu grass occupies much of the upper portion of the HFU and is particularly dense in the Upper
Maulua Unit. Kikuyu grass occurred with the highest frequency in sampled plots during a study by
Barnett and Simonson (2008). Between 1987-2007, the frequency of Kikuyu grass at HFU decreased
by 27.8 percent (Jacobi and Price 2007). Applications of the herbicide glyphosate have been tested to
control Kikuyu grass in endangered plant outplanting sites and koa outplanting sites. In addition, the
grass-selective herbicide Fluazifop-p-butyl (Fusilade) was tested as a post-plant application (Leary,
pers. comm.).
Koster’s Curse (Clidemia hirta)
Koster‟s curse is native to Central and South America and the Caribbean Islands. It has become
naturalized in several Pacific Islands, Malaysia, India, and eastern Africa. It was first found on O„ahu
in 1941 and subsequently spread to the other main Hawaiian Islands (DeWalt et al. 2004). On
Hawai„i Island, infestations occur at the Waiākea Forest Reserve, Puna, Kohala Mountains, and
above Laupāhoehoe (Smith 1992). The Koster‟s curse population at the KFU has increased rapidly
over the last 10 years along the lower road (Ball, pers. comm.).
This woody shrub grows to an average height of 6.6 ft. The stems are covered with red bristles and
the leaf surfaces are pleated (Whistler 1995). Koster‟s curse can be found in open pastures, riparian
areas, and roadsides, as well as in forest gaps and understory up to 4,921 ft elevation (DeWalt et al.
2004).
Several characteristics of Koster‟s curse contribute to its invasive potential in Hawaiian forests. It is
relatively shade tolerant and has no natural enemies in Hawai‟i. It is dispersed by a variety of
organisms including humans, birds, pigs, and mongooses (Smith 1992). Each plant produces over
500 small berry fruits, each containing over 100 very tiny seeds. These seeds can remain dormant for
up to 4 years. Furthermore, Koster‟s curse grows well in disturbed areas and can easily displace
native understory species (Smith 1992). This species is considered a noxious weed by the Hawai„i
Department of Agriculture.
Several biological control agents have been introduced against Koster‟s curse in the Pacific. On
Hawai„i Island, this includes Liothrips urichi, a thrip that attacks the terminal leaves and internodes
of Koster‟s curse (Hill et al. 2001, DeWalt et al. 2004). Because L. urichi prefers to lay eggs in open
areas, the thrip has reduced populations in open areas, but not forested habitats. A leaf-mining beetle
(Lius poseidon) and a fungus (Colletotrichum gloeosporioides) were also released throughout the
island to control Koster‟s curse (DeWalt et al. 2004). Collectotrichum gloeosporioides has caused
declines in Koster‟s curse on O„ahu; however, it requires repeated applications (Trujillo 2005). In
addition, Carposina bullata (Carposinidae) feeds on flower buds and Mompha trithalama
(Momphidae) feeds on flowers and berries (DeWalt 2006). None of these biocontrol agents have
caused declines in Koster‟s curse abundance in Hawaiian forest understory (DeWalt 2006). Koster‟s
curse is also susceptible to a number of herbicides (e.g., 2,4,5-T, 2,4-D, Trichlopyr) (Smith 1992).
Photinia (Photinia davidiana)
Photinia is listed as one of Hawai„i‟s worst invasive horticultural plants by DOFAW. The shrub
threatens mesic forests on Hawai„i and O„ahu from 4,500-6,000 ft
(http://www.state.hi.us/dlnr/dofaw/hortweeds/species/phodav.htm).
4-106 Chapter 4. Refuge Biology and Habitats