Biology Reference
In-Depth Information
Island, the most distant site being found 440 km from the nearest release. The dis-
ease developed rapidly, causing severe defoliation and significant decline in plant
height. As the mist flower cover significantly decreased as a result of the disease,
the species richness and mean percentage cover of native plants increased. It is
interesting to note that no significant change was observed in the species richness
and mean percentage cover of exotic plants (excluding mist flower). According to
Barton et al. (2007) the introduction of
E. ageratinae
as a biological control agent
of mist flower in New Zealand has been very successful (Fig. 10.2).
10.3 Bioherbicides
The bioherbicide approach utilizes indigenous plant pathogens isolated from weeds
and mass-produced in culture (Charudattan 1988). Pathogenicity tests are con-
ducted on the weed under a range of environmental conditions whereby field effi-
cacy and host-range tests are completed (Ayres and Paul 1990). Weed suppression
is obtained by applying the pathogen at rates sufficient to cause high infection lev-
els (Templeton 1982). Pathogen survival between growing seasons is often insuffi-
cient to maintain high infection rates and as a result new epidemics are not initiated
in the subsequent seasons which makes it necessary to repeat annual bioherbicide
applications (TeBeest et al. 1992).
10.3.1
Broad-Leaved Tree Species: Chondrostereum purpureum,
Cylindrobasdium laeve
The use of endemic wood-rotting fungi as bioherbicides to control invasive woody
weed species was successfully implemented in the Netherlands and South Africa
(Green 2003). Applied directly on freshly cut stump surfaces, these fungi prevent
resprouting of inoculated tree stumps. Both fungi are naturally present in native
forests and normally infect through wounds and natural openings in weakened
trees. They infect the cambial tissue and kill the tree. They are nearly 100% effec-
tive when applied as a bioherbicidal preparation to cut stumps, although the stumps
may resprout before being killed.
Chondrostereum purpureum
(Pers. ex Fr) Pouzar was developed as a control for
Prunus serotina
Ehrh. (
Rosaceae
), a North American tree that is invasive in parts
of Northern Europe. A mycoherbicide preparation under the name BIOCHON was
developed in the Netherlands, but the cost of registering it for commercial use pre-
cluded further development. An attempt was underway to offer it for use as a natu-
ral wood-decay promoter, but the Dutch authorities did not permit such unregistered
use. There might be some recent interest in using this fungus in German forests (De
Jong 2000; De Jong et al. 1990, 2007).
In Canada, two stump treatment products, Myco-tech
™
and Chontrol
™
(Yandoc-
Ables et al. 2006a), containing native isolates of
C. purpureum
have been developed
