Control of Tree Pear
A fact sheet to assist landholders undertake control of tree pear
Tree pear, or velvety tree pear (Opuntia tomentosa) as it is also known is the most widespread declared
pest plant in the Southern Downs Region. It can outcompete native plants and shade out pasture, as
well as making mustering difficult. Tree pear also provides a food source for feral pigs.
Tree pear is readily spread by birds and other animals, as well by flood waters – just because you may
only have a few old tree pear, it doesn’t mean they are not causing harm elsewhere.
It is declared as a Class 2 pest plant under the Land Protection (Pest and Stock Route Management) Act
2002, meaning all landholders must take steps to keep their land free from tree pear. Council routinely
undertakes control on its roads and other lands and undertakes property inspections to provide advice
to landholders and to ensure efforts are being made to prevent the spread of tree pear. While it is true
cattle will eat tree pear, it is not considered an effective means of control.
Description
Tree pear grows to about 5 – 6m tall with woody trunks exceeding 50cm in width. Pads (incorrectly
referred to as leaves) are up to 35cm long, dull green and covered in fine hairs. The stem and pads of
younger plants are dull green. Plants take several years before they develop red, egg-shaped fruit which
contain many seeds and red coloured pulp. Flowers are deep orange in colour.
Southern Downs Regional Council
Distribution
Tree pear occurs on all land types in the Southern Downs Region – from the traprock and granite soils in
the southern end of the region, to the cracking black soils and forest country in the north. There is
potential for spread beyond current infestation levels in all land types.
Tree pear is spread by birds and other
animals such as feral pigs that ingest the
many-seeded fruit and pass seeds through
their droppings. Pads can be moved by
animals and floodwaters and will readily take
root and grow at their new destination.
Impacts
The impacts of tree pear may not be obvious
until such time as density levels become
significant. However, due to its ability to
withstand drought, it will outcompete native
tree species. Large plants shade out pasture
and can provide harbourage for feral pigs. It can also make mustering difficult and is unpleasant to say
the least to come into contact with!
Control
Unlike many other weeds, control options for tree pear are limited to herbicide control. Mechanical
control is not effective as any part of the plant will re-shoot when knocked to the ground. Hot fires can
kill tree pear plants but in most cases is not a practical option.
There is a biological control agent (prickly pear cochineal) present in the environment that appears to
move around slowly and that can assist with control by stunting plant growth and reducing fruit set. The
agent can be moved around by collecting infested pads and placing them against uninfested plants. The
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presence of this agent will not provide control on its own – herbicide treatments must be undertaken to
achieve effective control.
Herbicide control
There are three methods of herbicide control available to kill tree pear. All are effective and each has its
place. Table 1 shows application rates and registered chemicals for each method.
Stem Injection
This method involves injecting herbicide into the sapwood of plants using either an axe or a tree spear.
The spacing of cuts and the dose of herbicide depends on the herbicide being used. It is important to
penetrate the bark layers and inject the herbicide into the sapwood. The photos below show an axe
being used to make the cuts and a drench gun being used to apply the herbicide to the cuts.
A tree spear can be used to do the same job as an
axe and drench gun. The spear is used to
penetrate the bark and to deliver the dose of
herbicide.
Landholders must be aware however that tree pear
will fall over much quicker following stem injection
than the other herbicide control methods and that
plants will still be very heavy when they fall. Consideration should be given to using other control
methods such as foliar or basal bark spraying when tree pear are growing on fence lines, next to roads
or adjacent to troughs. It may be worth moving stock out of treated paddocks when the first few plants
start to drop following injection.
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Foliar spraying
This method involves spraying a herbicide and
water mix over all surfaces of the plant i.e. all pads
and stems must be completely covered. Foliar
spraying is advised when plants are growing on
fences and roads. Plants remain upright until they
begin to rot and when they eventually fall over, will
not cause the damage injected trees can due to
being much lighter.
Foliar spraying generally uses more herbicide and
takes longer than stem injection and therefore is a
more expensive control option.
Basal bark spraying
This method involves spraying a diesel and herbicide mix onto the trunk of plants, from the ground to
about knee height, with coverage around the entire stem. Basal bark spraying adds the extra cost of
diesel and large plants may take several litres of spray mix to achieve adequate coverage. Treated trees
fall quickly, as with stem injection and it is also a more expensive control option than stem injection.
Choosing the most appropriate herbicide control option
Council has undertaken trials of the various herbicide control options with the aim of providing an
indicative control cost for landholders. The herbicides mentioned below are those regularly used by
Council in its control operations, but are not an exhaustive list of those registered for tree pear control.
The Australian Pesticides & Veterinary Medicines Authority web site (www.apvma.gov.au) should always
be consulted to get up to date herbicide registration information.
Product name
(first
registered)
Grazon Extra
Amitrole T
Amitrole T
Active
ingredient
Aminopyralid +
picloram +
triclopyr
Amitrole +
ammonium +
thiocyanate
Amitrole +
ammonium +
thiocyanate
Application
method
Application
rate
Cost per
mature tree
Foliar spraying
500mL/100L
water
$8.12
Foliar spraying
1:25 with water
$23.00
Stem injection
Neat chemical
$0.14
1mL per cut at
3cm spacing
2mL per cut at
2cm spacing
Roundup
Glyphosate
Stem injection
Neat chemical
$0.18
Access
Picloram +
triclopyr
Basal bark
1:60 with diesel
$8.40
Comments
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