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 arguably the worst variety of cactus – prickly pear – brought into Australia, and one of the most difficult to control!
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 can lay on top of the ground for months before eventually taking root and establishing as a new plant.
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 left shows how the segments attach; just imagine how animals are affected.
Consider the plight of dogs, for instance, when they use their teeth to try to remove segments from their paws – they end up with pieces stuck inside and outside of their mouths. The sharp thorns will even stick right through their tongues!
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.
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 in New South Wales, such as the Turon, Macquarie, Peel, Namoi, Gwydir and Horton valleys.
CONTROL METHODS – plough/fire/bury/spray/biological:
Ploughing, where possible/permitted, is probably the only way to totally eradicate an area of tiger pear. Tiger pear cannot survive on lands under constant cultivation.
Burning. Tiger pear can be severely impeded by fire – certainly thinned out and made easier for follow-up spraying before the grass comes back. A good burn will take out most of the loose tiger pear segments laying on the ground Tops of plants are easily damaged, but it takes a really hot fire to eliminate the butts. Take care if collecting/stacking plants for burning – apart from “getting attacked” by the plants, the small segments are easily scattered in the process. Burning is really only appropriate for small infestations (and, I have to include it – always in accordance with local bushfire requirements).
Burying tiger pear is an option for small infestations. The plants only have to be buried to the extent that their air supply is cut off. Take care to not scatter the small segments.
Herbicide treatment is recommended for small/isolated infestations, in areas where containment is very important eg river frontages, property boundaries, sensitive livestock 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 Fifth Edition, herbicide treatments include:
|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|
|Triclopyr 300 g/L+ picloram 100 g/L eg Grazon DS®/Ken-Zon® OR Triclopyr 300 g/L+ picloram 100 g/L + aminopyralid eg Grazon Extra®||High volume 500 ml + 0.05% (500 mL) Uptake spray oil in 100 L water or knapsack application 50mL plus 50mL Uptake spray oil in 10L of water||Apply to actively growing plants – see APVMA permit PER 14442 for more details (in force 23 October 2013 to 30 June 2018).Editor’s note: water-based mixtures are usually very slow acting – large plants can take months to die BUT big advantage is that if cochineal insects are present they will persist and help to control new seedling growth – LRT 24 October 2013|
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 (somebody once said it’s akin to picking fly shit out of pepper)! 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.
Recommended for tiger pear infestations in the warmer, northern 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 paddocks. And, tiger pear and flighty horses definitely DO NOT MIX.
Having said all that, biological control in many areas has effectively kept tiger pear infestations down to a level where grazing animals can still utilise the land. With some extra effort from the landholder, biocontrol can be even more effective.
There are two (2) biological control agents for tiger pear – cochineal and cactoblastis:
Cochineal insects (Dactylopious austrinus) are slow, but they are invariably more reliable and effective in the long term – compared to cactoblastis. The insects are very small, but their numbers can increase prolifically during the warmer months, peaking around April-May. The use of cochineal insects simply involves the manual transfer of cochineal-infested segments (photo, 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, left, (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, however, is by crawling along the ground until they find another tiger pear plant – or perish. 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). So, they need our assistance to get them into the pear areas. A bucket and a pair of tongs, and the simple transfer of infected segments into new plants work very well!
Tips to help the cochineal?
- Always remember cochineal insects are very delicate! They don’t like extremely hot weather. They don’t like cold weather, especially with rain which sometimes washes off their waxy-web covering. When transferring insects into a new plant (especially in the approach to winter) try to give them some protection from the elements. Cover the infected segments with parts of the plant, or branches, bark, cow pads etc. The perfect environment cochineal population can actually double
its number every five days under right conditions (i.e. dry, and a consistent temperature around 26-28°C)!
- Covering newly-infected plants with cardboard, plywood or even a bit of old corrugated iron (during the cooler weather) will offer the cochineal insects maximum protection from the weather. This photograph (right) demonstrates the point: lifting up the cardboard shows how the cochineal insects in that part of the tiger pear plant had thrived Oct – after what had been a long and cold winter). CAUTION: something to think about: 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. Worth noting that a cochineal population can actually double its number every five days under right conditions i.e. dry, and a consistent temperature around 26-28°C (JH Hosking 1987).
USE THE RIGHT COCHINEAL SPECIES… 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!
Cactoblastis (Cactoblastis cactorum) work differently to the cochineal insects. The cacto moths lay their eggs on the tiger pear plant (if the larvae can cause a lot damage to tiger pear in a short time – but they seldom finish the job. Their favourite food is the common prickly pear but if there’s not enough of that around, the cactoblastis moths will The larvae (black & orange striped “grubs” about 25mm long – photo, right) tunnel through the plant, hollowing out the limbs and segments of the plant (photo, below). Sometimes they destroy 90% of the plant. Often, their actions weaken and break up
the plant causing segments to break off and scatter even more than usual. (Not a problem if cochineal insects are also present in the plant – see cochineal above.
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. The moths will lay eggs on the tiger pear if they can’t find their preferred common pear species.
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.
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 06/09/09