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Identification
│
The problem
│
More information
│
Control methods
│Using
pesticides │Disclaimer
 Tiger pear (Opuntia
aurantiaca) is a native of South America. It is believed to have been
introduced as an ornamental garden plant during the early 1800's. Tiger pear is
the worst variety of cactus – prickly pear - brought into Australia, and the
most difficult to control! Photo, left, shows
an almost impenetrable patch of tiger pear on a property near Barraba in 1993,
before release of cochineal insects [photo - Peter Nolan, ex NSW DPI,Tamworth].
Photo on the right shows Paul Lutschini (Pear Commission, Mudgee) in amongst
tiger pear on a sheep camp on top of a hill in the Turon Valley near Bathurst.
Circa 1994.
 Tiger
pear is a menace to animals and humans – sharp thorns on each segment
contain tiny barbs which make removal of the thorns very difficult and painful.
Photo on right shows how the segments attach; just imagine how animals are
affected. For instance, dogs use their teeth to remove segments from their
paws - they then end up with pieces stuck inside and outside of their mouths.
The sharp thorns even stick right through their tongues!
IDENTIFICATION
 Tiger
pear is a low-growing, jointed, cactus plant. New plants start from segments,
not seeds. The two main growing periods for the plant are in February and
October when new, bright green shoots appear. These shoots can grow as long as
10cm in a couple of weeks. Plants develop to a height of around 60cm.
THE PROBLEM
 Tiger
pear can cause painful injury to animals or humans who accidentally walk into or
otherwise touch a plant. A typical tiger pear plant is made up of many joined
"segments", which are covered in sharp, 25mm spines. The segments, easily
detach from parent plants and attach to passing animals, humans or even to the
tyres of motor vehicles. Dislodged tiger pear segments are very hardy. They
often lay on top of the ground for months before eventually taking root and
establishing as a new plant.
Floodwaters carry tiger
pear segments over long distances. Animals then carry the segments back into
the hills. Tiger pear infests many of our major river systems, such as the
Turon, Macquarie, Peel, Namoi, Gwydir and Horton valleys.
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CONTROL METHODS
Ploughing,
where possible,
is probably the only way to totally eradicate an area of tiger pear. Tiger pear cannot survive on lands
under constant cultivation [NB. State laws apply in respect of land clearing.]
Burning.
Tiger pear can be destroyed by fire. Tops
of plants are easily killed, butts require extra heat. Take care when collecting
plants or stacking wood on top – the small segments are easily scattered.
Burning is really only appropriate for small infestations. [NB. Subject to
compliance with local bushfire restrictions].
Burying tiger pear
is an option for small infestations. The plants only have to be buried to the
extent that the air supply is cut off. Take care because the small
segments are easily scattered.
Chemical treatment
is recommended for small/isolated infestations, in areas where containment is
important eg river frontages and property boundaries, or in areas where
biological control has not proven to be effective because of climatic or other
conditions. According to NSW DPI’s excellent booklet “Noxious and
Environmental Weed Control Handbook 2004/2005”, herbicide treatments
include:
|
Chemical |
Rate |
Comments |
|
Triclopyr
Garlon 600® |
3.0 L in 100 L water
OR 1.0 L in 75 L distillate |
Apply as a thorough
foliar spray |
|
Triclopyr + Picloram
Access® |
1.0 L in 60 L diesel |
Folia application,
thoroughly wet plants |
It’s not hard to kill a
single tiger pear plant, BUT, finding
all the small plants and loose segments scattered around the ground is the real
challenge! Spraying tiger pear is a job that just cannot be rushed. And,
repeated treatments are necessary.
IMPORTANT:
USE OF PESTICIDES – ALWAYS READ THE LABEL
Pesticides must only be used for the purpose for which they are registered and
must not be used in any other situation or in any manner contrary to the
directions on the label. Never use a herbicide in any way contrary to the label
recommendations.
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BIOLOGICAL CONTROL
is recommended for tiger pear infestations in the warmer, northern western areas
of New South Wales, and it's particularly useful in rough or inaccessible
country. But, biological control is very slow - it never gets rid of all the
pear - and is not recommended for small patches, sensitive property boundaries
or intensely-grazed paddock. And, tiger pear and flighty horses definitely DO
NOT MIX.
There are two (2)
biological control agents for tiger pear – cactoblastis and cochineal:
1. Cactoblastis
(Cactoblastis cactorum) insects are capable of causing a lot of damage
to tiger pear – but they are usually unreliable. The larvae (black & orange
striped “grubs” about 25mm long) tunnel
 through the plant, hollowing out the
limbs and segments of the plant (photo, left). Sometimes they destroy 90% of the plant.
Unfortunately, their actions weaken and break up the plant causing segments to
break off and scatter even more than usual. (Not so much of a problem if
cochineal insects are also present in the plant – see cochineal below).
Assisting the further distribution of cactoblastis? Apart from some
stacking of prickly pear plants to encourage visits from the (egg-laying)
cactoblastis moths, there is no really effective way to assist build-up of
cactoblastis numbers in tiger pear. Moving infected tiger pear pieces from one
plant to another can help sometimes.
2.
Cochineal
(Dactylopious austrinus) insects are not as fast or as “hungry” as
cactoblastis may sometimes appear to be, but they are usually more reliable and
effective in the long term. They work at their best during summer/autumn,
usually peaking around April-May. The use of cochineal insects simply involves
the manual transfer of cochineal-infested segments (such as the one in the
photograph on the right) into plants that do not contain cochineal insects!
 Assisting the further distribution of cochineal? Cochineal start their
lives as a tiny, crawling insect, venturing off to locate a new food source.
Their dispersal method includes being blown by the wind, which is great if the
wind takes them to a patch of tiger pear! This sketch (courtesy VC
Moran & BS Cobby, 1979, Rhodes University, Grahamstown, S. Africa) shows the "hairs" which act as sails in the wind. Their main means of travel is by
crawling along the ground until they find a plant.
Cochineal insects can only travel along the ground for about 4 or 5 metres (if
there are cracks in the ground, eg as in black soil, they don’t get that far).
They need our assistance to get them into the pear areas. A bucket and a pair
of tongs, and the simple movement of infected segments into new plants is the
answer.
Tips to help the cochineal?
-
Always remember that
cochineal insects are very delicate. They don’t like cold and wet weather.
When you put the insects into a new plant (especially in the approach to
winter) give them some protection from the elements. Cover the infected
segments with parts of the plant, or branches, bark, cow pads etc.
-
 Covering
newly-infected plants with cardboard, plywood or even a bit of old corrugated
iron will offer the cochineal insects maximum protection from the weather.
This photograph on the left demonstrates the point: cochineal thrived under the
cardboard (Bingara 16 Oct 02 after what was a lo ng and cold winter).
CAUTION: snakes may also take up residence under these protective coverings.
-
Another trick is to breed
the insects indoors, in readiness for release in early summer, the optimum
time for release. Store infected plant material in cardboard boxes in a dry,
warm area. Over a period of 6 to 8 weeks, you’ll have good supplies to put
out when the weather warms up.
USE THE RIGHT COCHINEAL…
Tiger pear, common pear and rope pear cochineal all look the
 same.
But, they’re each specific to their host plants. Only tiger pear cochineal –
Dactylopious austrinus - works on tiger pear!
MORE INFORMATION
Cochineal.htm
on this website. Information on
individual prickly pear
species is also included in this website. Return to
Weeds List for rope pear, harrisia, velvety tree pear, prickly pear
history etc.
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DISCLAIMER: The information contained in this
web site is based on knowledge and understanding at the time of writing.
However, because of advances in knowledge, users are reminded of the need to
ensure that information upon which they rely is up to date and to check currency
of the information with the appropriate officer of North West Weeds or the user’s independent adviser.
LRT 28/06/06
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