Biology Reference
In-Depth Information
(Trujillo 2005). After several spore formulations were tested for field applications,
a 5 × 10
5
per mL spore suspension amended with 0.5% gelatin and 2.0% sucrose
that caused severe defoliation was selected. Annual sprays directed at clidemia in
Aiea State Park, Oahu using this spore formulation resulted in effective control of
the weed and in the regeneration of several native species such as
Acacia koa
and
fern species (Trujillo 2005).
10.3.3 Hedychiumgardnerianum-Ralstonia
solanacearum: Use of a Bacterial Pathogen
Native to India,
Hedychium gardnerianum
Sheppard ex Ker Gawl. (wild ginger or
kahili ginger, Zingiberaceae) is widespread throughout the tropics and invasive in
many forest ecosystems including Hawaii, New Zealand, Reunion, South Africa,
and Jamaica (Anderson and Gardner 1999). In 1954,
H. gardnerianum
was brought
into Hawaii as an ornamental plant where it subsequently escaped cultivation and
is currently considered a naturalized plant species. According to Anderson and
Gardner (1999), kahili ginger has invaded 500ha of Hawaii Volcanoes National
Park forests (1,000-1,300-m elevation) and is found on all islands in Hawaii (Smith
1985). Displacing native plants in forest ecosystems, kahili ginger forms dense
stands that smother the native understory. Further spread is facilitated by the rhi-
zomes making this weed difficult to control (ISSG Database 2006). Because of the
fact that kahili ginger is widely distributed throughout the Hawaiian national parks,
environmental concerns regarding herbicide use to control kahili ginger have
resulted in biological control being considered as the only practical approach for
long-term management of this invasive weed in native forests.
A Hawaiian
Ralstonia
(=
Pseudomonas
)
solanacerum
(Smith) Yabuuchi et al.
strain was isolated from both edible (
Zingiber officinale
Roscoe) and ornamental
gingers. While the isolate from edible ginger was less virulent than the isolate from
ornamental ginger, the two isolates were proposed to be one strain based on similar
cultural and pathogenicity characteristics (Anderson and Gardner 1999).
Ralstonia
solanacerum
systemically infects edible and ornamental gingers causing decay and
wilting of the infected tissue. Host specificity tests showed that this bacterium
did not infect the native and cultivated solanaceous species tested. All inoculated
H. gardnerianum
plants including rhizomes developed symptoms within 3-4 weeks
after inoculation, with most inoculated plants completely dead within 4 months
(Anderson and Gardner 1999). While limited infection occurred close to the inocu-
lation sites on
H. coronarium
J. Koenig,
Z. zerumbet
(L.) Sm.,
Heliconia latispatha
Benth., and
Musa sapientum
L., no further systemic infection was observed in these
species and the plants continued to grow normally (Anderson and Gardner 1999).
Despite concerns about the potential negative impacts of the bacterium on the edi-
ble ginger,
Z. officinale
, Anderson and Gardner (1999) concluded that kahili ginger
infestations were often remote enough to limit the risk of contamination to edible
ginger plants. The use of
R. solanacerum
to control of
H. gardnerianum
in Hawaii
