Blackberry control manual - Weeds Australia

Septoria leaf spot (Septoria rubi)
This leaf spot is very rare and is identified
by purple-brown blotches 1 – 2 millimetres in
diameter on the upper surface of the leaf. The
blotches sometimes have a white centre. There is
never a corresponding yellow or black, powdery
pustule on the lower leaf surface.
Cercospora leaf spot (Cercospora rubi)
Cercospora infection is another very rare disease.
It is identified by the presence of brownish
blotches 5 – 7 millimetres in diameter on the
upper surface of the leaf. These sometimes have a
purple fringe but never a corresponding yellow or
black, powdery pustule on the lower leaf surface.
Case study
Integrating biological control with
chemical control methods
The problem
Chemical or physical blackberry control methods
are difficult to implement in many places and
impossible in others because of insufficient access
to the infestation. Sections of the blackberry
population regrow with vigour, and together with
new seedlings and root propagules they become
an ongoing and expensive problem.
The trials
Trials were conducted across eight Western
Australia sites to look at the synergistic effects
of using the leaf rust and the herbicide treatment
most commonly used in the region (metsulfuronmethyl
with Pulse®). This herbicide takes a full
season to kill the plant and was applied early in
the growing season so that the interaction with
the rust could be monitored.
The results
Despite the rust being reared and released in a
consistent way, there was a significant variation
in the level of infection from site to site. The drier
sites had hardly any rust, whereas in the wetter
sites there was a large amount of rust present,
with diseased leaves falling off and canes dying.
Herbicide control was more consistent across the
sites but did not result in a 100% kill at any site.
Generally, crowns and canes with new growth
were killed, whereas smaller root suckers, not
actively growing at the time of spraying, survived.
Rust did not develop on plants sprayed with
herbicide in the same year as rust release.
Although the herbicide did not kill the plant
immediately, it did prevent new growth, which is
essential for the establishment of the rust.
It became obvious that any potential results from
combining herbicide treatment and biological
control can occur only over a prolonged period
of successive years. For example, the rust may
infect and suppress the new growth of plants that
have survived herbicide treatment in a previous
year. Likewise, prior infection by the rust may
weaken large blackberry plants making them more
susceptible to herbicide treatment the following
year.
Implications of the study
• Plants treated with herbicides will not become
infected by the rust during the season of
treatment.
• Integration of biological control with herbicide
applications is more valuable when inaccessible
areas are left untreated to allow the rust
population to build up and accessible areas
are treated with chemical or physical control
methods.
• The rust will reduce the vigour and invasiveness
of the untreated plants and minimise the
reinvasion of the treated areas. It can also
potentially infect any plants that have survived
treatment with herbicides.
Further information on integrating herbicides
with biological control can be found at
www.ento.csiro.au/weeds/blackberry/
WABBManPlan2006_draft.pdf
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