Technical highlights - Department of Primary Industries ...

8. Biological control of bellyache bush (Jatropha gossypiifolia)
Project dates
July 2007 – June 2012
Project leader
Dr K. Dhileepan
Ecosciences Precinct
Tel: (07) 3255 4449
Email: k.dhileepan@deedi.qld.gov.au
Other staff in 2010–11
Mariano Treviño
Objectives
• Identify suitable biological control
agents for host-specificity testing
through review of earlier survey work
and exploration (in collaboration with
the CSIRO).
• Conduct pathogenicity and host
range testing of the Jatropha rust
fungus (Phakopsora jatrophicola)
as a potential biocontrol agent for
bellyache bush.
Rationale
Bellyache bush (Jatropha gossypiifolia)
is a serious and expanding weed
of northern Queensland. It invades
rangeland, particularly in riparian
zones, and forms dense thickets that
reduce productivity and biodiversity.
All parts of the plant, especially the
seeds, are toxic to grazing animals.
Bellyache bush is a declared target
for biological control and an effective
biocontrol agent is needed to halt further
spread and reduce its impact. The
only biological control agent released
to date, the bellyache bush jewel bug
(Agonosoma trilineatum), is not known
to be established in the field. Hence,
the bellyache bush biological control
program was recommenced in 2007 to
further screen potential agents identified
during earlier surveys in Central
America and to conduct additional
surveys in South America.
Methods
Staff from the CSIRO Mexican Field
Station and CABI Europe – United
Kingdom (CABI Europe–UK), through
other collaborative links, collect fresh
spore material of Phakopsora jatrophicola
ex J. gossypiifolia from different
geographic regions and send them to
facilities at Egham, United Kingdom.
In order to quantify the degree
of susceptibility of individual
J. gossypiifolia varieties towards
particular P. jatrophicola strains, we
inoculate rust strains from Brazil,
Trinidad and the Pacific coast of Mexico
on the three varieties Queensland
Bronze, Queensland Green and
Queensland Purple. The rust strain most
virulent towards all Queensland varieties
of J. gossypiifolia is then selected for full
host-specificity tests conducted under
quarantine by our collaborators at CABI
Europe–UK.
Virulence (pustules plant –1 )
-
250
200
150
100
Virulence
50
(pustules plant
0
Progress in 2010–11
All three Queensland bellyache bush
varieties were susceptible to all three
rust strains, but the strain from Trinidad
showed consistently high virulence on
all three Queensland bellyache bush
varieties (Figure 8.1). The strains from
Brazil and Trinidad were also less virulent
than the previously assessed rust strain
from El Zapote, Mexico, towards the
non-target plant J. curcas. Because of its
comparatively high virulence towards all
Queensland varieties of J. gossypiifolia
and its low virulence towards J. curcas,
the strain from Trinidad was selected for
host-specificity testing.
Full host-specificity testing of the rust
strain from Trinidad has commenced.
In March 2011, we exported a shipment
of 13 test plant species (10 plants each) to
CABI Europe–UK. The evaluation status
and test results of the 13 non-target
species are summarised in Table 8.1.
The rust caused restricted sporulation on
J. multifida as well as on one individual
plant of J. integerrima with hirsute
leaves. Other individuals of J. integerrima
exhibiting non-hirsute, waxy leaves
proved to be less susceptible. J. podagrica
showed chlorotic and necrotic leaf spots,
but no sporulation, following inoculation.
No macroscopic symptoms or sporulation
were evident on other test plant species.
Pacific strain Trinidad strain El Zapote strain standard error
Queensland Bronze Queensland Green Queensland Purple
Bellyache bush variety
Figure 8.1 Virulence of three strains of P. jatrophicola towards the three Queensland bellyache
bush varieties
Part 1 Integrated weed management 19