Blackberry control manual - Weeds Australia

Case study
Consider the long-term effects when
selecting herbicides
Rubus anglocandicans and R. ulmifolius occurred
in continual thickets along the banks of the
Warren River in Western Australia among mature
native vegetation, including trees, and other
shrubs, herbs, grasses and sedges.
A mixture of glyphosate, metsulfuron-methyl
and Pulse® was used at recommended rates
over several years to control the blackberry. This
resulted in the total removal of all vegetation
except the large trees. This in turn led to
excessive erosion and riverbank collapses.
Had only metsulfuron-methyl been used in this
situation, the sedges and grasses would have
been retained, erosion may not have been a
problem, and the intense level of revegetation
now required to rectify the problem may not have
been necessary.
When selecting herbicides, it is important to
assess the situation and consider the long-term
effects on non-target species.
Variation in herbicide application
Differences in the way herbicides are applied
results in wide variation in the control achieved.
Herbicide labels clearly describe herbicide
dilution rates but less specifically indicate how
wet the bushes should be after application
(e.g. ‘wet leaves and canes thoroughly’ or ‘use
3000 – 4000 L/ha of spray’). Although dilution
of herbicide can be accurately controlled, the
correct wetting of bushes is a greater challenge.
The most common error when spraying
blackberry is to under-spray large bushes.
Such bushes have an extensive surface area
comprising the canopy, as well as leaves and
canes at the centre of the plant. Spray operators
may see that the outer foliage (canopy) appears
wet and decide the plant is sufficiently sprayed.
However, the inner parts of the bush may have
received virtually no treatment. Experienced
operators ensure that these larger plants get
sufficient wetting of the inner leaves and canes.
Rule of thumb: Knowing the volume of
spray to apply to each bush when spraying
blackberry is critical to achieving a good
result but very difficult to do in practice.
As an example, a bush five metres in
diameter and two metres high would require
approximately 14.9 litres of spray (based
on 3000 – 4000 L/ha). See ‘Type and rate of
herbicide used’ (p. 43) for more details.
For spraying purposes, a blackberry plant should
be viewed in three dimensions. The target
plant is not a flat (two-dimensional) plane but a
three dimensional object.
The most important factor is the amount
of herbicide applied to the bush. Generally,
lower volumes of water can be used if the
concentration of herbicide is increased.
A study of 15 spray operators showed a
300% to 400% difference in volumes applied
to treat the same bush. In this controlled
study, all the applicators followed the same
label directions and operated the same
equipment. The large discrepancies in spray
volumes were responsible for poor control
due to under-spraying or increased costs
from over-spraying.
One Weeds Officer’s tip is: When spraying
large infestations over a period of time, mark
the areas already treated by tagging each
bush with toilet paper. Toilet paper lasts
longer than marker dye, is cost effective and
eventually degrades without causing any
environmental damage.
Timing of herbicide applications
The optimum time to spray blackberry is when
it is actively growing from flowering through
to fruiting – usually during December, January,
February and March. However, this may vary
between regions and species.
Blackberry can be sprayed before and after
these months if conditions are suitable. Spraying
summer active perennials like blackberry in
autumn can increase the amount of herbicide
translocated into the root system, because
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