Biology Reference
In-Depth Information
and registered. Through extensive epidemiological studies, it has been established
that the this fungus posed no threat to susceptible crops grown further than 500 m
from the application site (De Jong et al. 1990). The use of this control method will
only have a limited impact on nontarget trees since the fungus spores are ubiquitous
and healthy trees are resistant to attack. However, Setliff (2002) showed that
C.
purpureum
is an important pathogen with epidemic potential in forest tree species
especially in the Betulaceae (
Betula
and
Alnus
) and the Salicaceae (
Populus
and
Salix
). Using this fungus as an inundative biological control agent should be con-
sidered within this perspective rather than as a sporadic pathogen of fruit trees. A
thorough investigation into the ecological impacts of
C. purpureum
for each geo-
graphical region should be undertaken with the purpose of identifying low disease
risk areas where
C. purpureum
can be applied with the minimum environmental
impact (Setliff 2002).
Exploratory studies in New Zealand have shown that
C. purpureum
could be
used to prevent resprouting of cut gorse (
Ulex europaeus
L.,
Fabaceae
) bushes
(Bourdôt 2007). One year after treatment of stumps with mycelium on agar or
mycelium formulation, basidiocarps of the fungus were present on 15 of the 16
treated stumps. Seventeen months after treatment, half of the
C. purpureum
-treated
stumps were dead as compared with the untreated stumps (Fig. 10.3). These results
confirm that
C. purpureum
has potential as a biological control agent for gorse
(Bourdôt 2007; Bourdôt et al. 2006).
In South Africa, a basidiomycete,
Cylindrobasidium laeve
is registered as the
bioherbicide, Stumpout. It is applied directly to freshly cut stumps of several inva-
sive
Acacia
spp. According to Morris et al. (1999), Stumpout kills 95-100% of
resprouting stumps.
10.3.2
Clidemia hirta-Colletotrichum gloeosporioides
f.sp. clidemiae
Clidemia hirta
(L.) D. Don (Koster's curse,
Melastomaceae
) is a perennial shrub
native to Central and South America, and the islands of the West Indies (Wester and
Wood 1977, Peters 2001). It is invasive in tropical forest understories particularly
in the Hawaiian Islands, and its negative effect on the native ecosystem (Gerlach
2006) has led to the fear that similar effects will be felt in the other introduced
regions including the Seychelles, the Comoros Island, Réunion, Mauritius, the
Malaysian Peninsula, and parts of Micronesia (Palau) (Gerlach 2006). First reported
in Oahu in 1941 (Trujillo 2005),
Clidemia
populations reached significant propor-
tions by 1984 with infestation extending over 60,000 ha of forested areas of Kauai,
Molokai, Maui, and Hawaii (Trujillo 2005). All management strategies including
physical removal and herbicide treatments were not practical and generally failed
especially when initiated after first fruit set.
A fungus,
Colletotrichum gloeosporioides
(Penz.) Penz. f. sp.
clidemiae
was
isolated from diseased clidemia leaves collected in Panama in 1985 (Trujillo 2005).
