Blackberry control manual - Weeds Australia

Case study
Burning blackberry
The use of fire to control blackberry is generally
ineffective: even though stems are destroyed, the
woody crown and root system are only slightly
affected. Even after the intense wildfires in the
ACT in 2003, officers from Parks, Conservation
and Lands (PCL) found that regrowth occurred
from root systems in the next year.
Researchers investigated whether the crown
and root system were affected by the intensity
of the fire. They chose a number of plots after
the intense fires in Victoria in 2003. They found
that all the blackberry plants survived the fire,
but there was no simple relationship between
blackberry recovery and pre-fire blackberry
abundance.
In one plot there was a large number of crowns
pre-fire but a low blackberry density two years
later. One possible explanation for this is a
combination of a hot fire and shallow stony soil;
this would have reduced the blackberry roots to
a few fragments and led to regrowth that was
unable to compete successfully with native shrubs
and trees establishing from seed.
In other plots, dense blackberry stands became
established with little competition from natives.
These plots had been farmland or had only a
sparse native vegetation cover where the native
vegetation seed bank had been depleted before
the fire.
The researchers suggested that an effective postfire
intervention may be to perform heavy seeding
with local native shrubs. This observation was
echoed by PCL staff:
What we ideally need to be able to do is burn dead
canes after we have sprayed them so we can plant
or seed native plants. Otherwise we end up with
weeds or eventually new blackberries growing
among the protection of old dead canes.
PCL staff also noted that it was important to allow
enough blackberry biomass to regenerate after a
fire before the plants were treated with herbicides;
otherwise the growing canes would not convey
sufficient chemical to the crown and root system
to kill them.
4.3 Biological control
Biological control is the use of natural enemies
such as diseases, mites and insects to suppress
and weaken the target weed.
Biological control programs assess the pests and
diseases found on overseas populations of the
weed. After rigorous testing, these agents are
released, mass-reared, and distributed into weed
populations across Australia. However, not all
agents become established effectively or have
an impact on the weed. The diverse nature of
the Australian environment often results in some
agents doing well in some localities and not
others.
Currently the only biological control agent tested
and released into Australia is the leaf rust fungus
(Phragmidium violaceum), which attacks only
European blackberry. The rust is highly efficient
at spreading by natural means and will colonise
blackberry when environmental conditions are
suitable. Therefore, land managers do not need
to redistribute the rust.
There are also other diseases and pests of
blackberry present in Australia. They are less
useful as tools for controlling blackberry because
they can potentially also attack native blackberry
species or commercial species. They include
the leaf eating mite (Acalitus essigi), blackberry
orange rust (Kuehneola uredinis), Septoria leaf
spot (Septoria rubi) and Cercospora leaf spot
(Cercospora rubi).
The blackberry leaf rust fungus
The blackberry leaf rust fungus (Phragmidium
violaceum) is effective only on European
blackberry species. It does not infect American
or Asian species, species native to Australia,
or commercially grown species like raspberry,
loganberry, boysenberry and youngberry.
Blackberry leaf rust fungus primarily attacks the
leaves of blackberry and causes defoliation. It
can also be found on flower buds and unripe
fruit. The tips of the heavily attacked stems die
back, preventing the production of daughter
plants at the end of the stems. The rust also
obtains nutrients and water from the blackberry
plant cells, reducing the plant’s overall ability to
grow and reproduce.
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