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

Hakalau Forest National Wildlife Refuge
Comprehensive Conservation Plan
Figure 4-7 demonstrates an example of the survey and monitoring scheme for invasive weeds at the
HFU utilizing existing transect lines also utilized for forest bird and ungulate surveys.
Kona Forest Unit
The results of the invasive plant surveys conducted on the KFU have not been compiled. The Final
Environmental Assessment for Fencing of the Kona Forest Unit of the Hakalau Forest National
Wildlife Refuge (2008) identifies the following nonnative plants as management concerns:
strawberry guava, Christmas berry, banana poka, Koster‟s curse, Florida blackberry, German ivy,
and nonnative pasture grasses.
Invasive plant control has not been conducted at the KFU, but will commence following the
construction of an ungulate-proof fence and with staffing/funding. After fencing, the Refuge will
work with available staffing and partners (e.g., Three Mountain Alliance) to survey and conduct
control efforts as needed. Weed management will be mostly above 3,600 ft because understory below
this elevation is mostly invasive plants and is too degraded. This work will be conducted from higher
elevation to lower elevations to reduce further spread of invasives.
Banana Poka (Passiflora mollissima)
Banana poka, a vine native to South America, was introduced to the Hawaiian Islands in the early
20 th century. The plant tolerates a wide range of environmental conditions and has a rapid growth rate
(LaRosa 1992). In Hawai„i, banana poka invades disturbed forest gaps and forms curtains that
exclude available light for native forest trees (USFWS 1996b). Banana poka is dispersed by pigs,
cattle, and game birds, which eat the fleshy fruit and disperse seeds (NRCS 2005).
A combination of herbicide, manual removal, and biocontrol has been used to control this species.
Applying herbicide to cut stems has shown to control some infestations (LaRosa 1992). Banana poka
infestations on Hawai„i Island have also been controlled by the introduced fungus Septoria
passiflorae; however, this biocontrol agent is not effective on the Kona side of the island where acid
rain inhibits the germination of S. passiflorae spores (Trujillo 2005). The passion vine butterfly was
also introduced, but control was not successful (LaRosa 1992).
The species is largely concentrated in the Upper Maulua Tract of the HFU, initially infesting about
3,000 ac, but the area has been reduced by manual removal. A total of 210 ac were controlled from
2006-2007. The eradication of pigs has also contributed to its control (NRCS 2005). Grazing by
cattle presently helps to control the spread of this species on the KFU; thus, banana poka control
measures will be needed following the removal of cattle.
Investigations at the HFU found that banana poka nectar is three times more concentrated than „ōhi„a
nectar. It provides the three main sugars (glucose, fructose, and sucrose). However, passerines do not
express the digestive enzyme for the disaccharide sucrose and therefore can only obtain 5 percent
“digestible” sugars from the banana poka nectar (Kapono, pers. comm).
Christmas Berry (Schinus terebinthefolius)
Christmas berry is an aggressive, rapidly spreading plant native to Argentina, Brazil, and Paraguay. It
can grow as a tree or shrub up to 23 ft in height. Christmas berry has become naturalized in mesic,
4-100 Chapter 4. Refuge Biology and Habitats