Technical highlights - Department of Primary Industries ...

9. Biological control of parthenium (Parthenium hysterophorus)
Project dates
May 2007 – June 2014
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 and Kelli Pukallus
Asad Shabbir and Ruey Toh (The
University of Queensland PhD students)
Objectives
• Monitor the field persistence and
abundance of parthenium biological
control agents.
• Evaluate the role of beneficial
competitive plants to enhance the
effectiveness of weed biological
control agents.
Rationale
Parthenium (Parthenium hysterophorus)
is a WONS and a Class 2 declared weed
in Queensland. Biological control is one
of the most effective and economically
viable management options for this
weed. Among the various biological
control agents introduced against
parthenium in Queensland, the summer
rust (Puccinia xanthii var. partheniihysterophorae,
previously reported
as P. melampodii) is an agent suited
to areas with hot and dry weather
conditions. It was introduced from
Mexico in 1999 and released at more
than 50 infested sites in Queensland.
The clear-wing moth (Carmenta ithacae),
also native to Mexico, was released
from 1998 to 2002. The stem-galling
weevil (Conotrachelus albocinereus) from
Argentina was released in Queensland
from 1995 to 2000. Although all three
agents have established in the field, their
incidence and abundance in parthenium
infestations in central and northern
Queensland is not fully known.
The role of competition from beneficial
plants in managing parthenium is widely
known. So far, however, no information
is available on the potential role of
various native and introduced pasture
plants in enhancing the effectiveness
of parthenium biological control agents
in Australia. Identification of beneficial
plants exhibiting high competitive
indices, in particular under changing
climate—specifically elevated carbon
dioxide (CO 2 )—would help to manage
parthenium more effectively.
Methods
Biological control agent
monitoring
Parthenium sites in central and northern
Queensland are monitored at the end
of the parthenium growing season. At
each site, we record the incidence and
abundance of various biological control
agents—the summer rust (P. xanthii var.
parthenii-hysterophorae), the clearwing
moth (C. ithacae) and the stemgalling
weevil (C. albocinereus)—along
with information on other established
biological control agents and the
abundance of parthenium.
Biological control and competitive
plants under elevated CO2 We conduct an experiment in controlledenvironment
rooms to quantify the
combined effect of a stem-galling
biological control agent (Epiblema
strenuana) and plant suppression
by buffel grass (Cenchrus ciliaris)
on parthenium’s vegetative and
reproductive growth under ambient CO2
levels of 380 parts per million by volume
(ppmv) and under elevated CO2 levels
(550 ppmv).
Parthenium canopy architecture
Parthenium canopy architecture is studied
under three temperature (day/night
22/15 °C, 27/20 °C, and 32/25 °C in thermal
time 12/12 hours) and two CO2 (ambient
and elevated) regimes in controlledenvironment
rooms. Identical light
(photoperiod 12 hours, ~ 250 μmol s –1 ) and
relative humidity (65%) are maintained
in all rooms. We track plant development
from the ninth day after transplantation
using three-dimensional digitising
every third day with a sonic digitiser.
The last measurement is made after
about 550 growing degree days. From
empirical data, we develop a virtual threedimensional
canopy architecture model of
a parthenium plant using the modelling
software L-systems.
Progress in 2010–11
In central Queensland, we surveyed
17 sites in March 2011. Surveys at three
sites in northern Queensland were
conducted in April 2011.
Parthenium summer rust
The summer rust was evident at all
sites with parthenium infestations. The
proportion of infected plants was high
at all three sites in northern Queensland
(Cardigan Station, Felspar and Plain
Creek), but the proportion of leaves with
rust infection remained low at all these
sites (Figure 9.1). In central Queensland,
parthenium was evident in only 7 of
the 17 sampling sites, but the summer
rust was observed at all sites with
parthenium infestations. The proportion
of plants and leaves infected varied
widely between sites (Figure 9.1).
Parthenium clear-wing moth
We have previously confirmed field
establishment of the clear-wing moth at
5 of the 13 release sites and 2 nearby nonrelease
sites in central Queensland. In
2011 the clear-wing moth was recovered
from a non-release site near Carfax,
confirming its continued persistence in
the field. High summer rainfall resulting
in flooding could have affected the rootboring
larvae at many sites.
Parthenium stem-galling weevil
The stem-galling weevil was not
recovered in any of the survey sites.
Limited establishment of this agent
could be due to the dominance of the
stem-galling moth (E. strenuana) in all
parthenium-infested areas. The stemgalling
moth and the stem-galling
weevil share a similar feeding niche.
Part 1 Integrated weed management 21