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Prickly pear

This Weed Risk Management Assessment uses a series of questions to arrive at scores for weed risk and feasibility of coordinated control for this weed, and displays the necessary management actions derived from these scores.

This information is then used to make decisions about the introduction, prioritisation and status of this weed in New South Wales.

Weed (Scientific name) Opuntia species excluding Opuntia ficus-indica (Indian Fig)
Weed (Common name) various prickly pears including; common pear, tiger pear, smooth tree pear and velvety tree pear
Region All of NSW
Management area Mostly rangeland in western NSW
Landuse 2.1 Grazing natural vegetation
Assumptions Prickly pear species- see notes below. Cactaceae.  Standard weed management is limited. Varied stocking rates most common. Fire used in some instances. Very little use of broad-scale herbicide applications and cultivation. Biological control effective- see notes. Density in land use - light (in general). 
Weed Risk
Invasiveness Score      Total Answers Source and comments
Q1. What is the ability of the weed to establish amongst existing plants? ? Do not know Do not know.
Q2. What is the weed's tolerance to average weed management practices in the land use? 2.0 Between 50 and 95% of weeds survive Estimate based on Parsons and Cuthbertson (2001) - incl. widespread use and success of biological control.
Q3. What is the reproductive ability of the weed in the land use? 2.0   a. Parsons and Cuthbertson (2001), pg. 359-368. This is from seed (in seed producing species and shorter times may occur from transplanted segments.
b. Not specified in reference, nor in other internet documents. 'Do not know' although likely to be >1000.
c.  Parsons and Cuthbertson (2001), pg. 359-368.
(a) Time to seeding 0.0 >3 yrs/never
(b) Annual seed production ? Do not know
(c) Vegetative reproduction 2.0 Frequent
Q4. How likely is long-distance dispersal (>100m) by natural means? 3.0    Parsons and Cuthbertson (2001), pg. 359-368. 
(a) Flying animals 2.0 Common
(b) Other wild animals 2.0 Common
(c) Water 2.0 Common
(d) Wind 1.0 Occasional
Q5. How likely is long-distance dispersal (>100 m) by human means? 2.0   Parsons and Cuthbertson (2001), pg. 359-368.
(a) Deliberate spread by people 1.0 Occasional
(b) Accidentally by people and vehicles 2.0 Common
(c) Contaminated produce 0.0 Unlikely
(d) Domestic/farm animals 1.0 Occasional
Total 7.0   
Impacts Score      Total   
Q1. Does the weed reduce the establishment of desired plants? ? Do not know Do not know'.
Q2. Does the weed reduce the yield or amount of desired vegetation? ? Do not know Do not know'.
Q3. Does the weed reduce the quality of products, diversity or services available from the land use? 1.0 Low Degrades appearance of areas where it infests
Q4. What is the weed's potential to restrict the physical movement of people, animals, vehicles, machinery and/or water? 3.0 High Parsons and Cuthbertson (2001), pg. 359-368 - closer to this than medium.
Q5. What is the weed's potential to negatively affect the health of animals and/or people? 2.0 Medium Parsons and Cuthbertson (2001), pg. 359-368.
Q6. Does the weed have major positive or negative effects on environmental health? 1.0   References do not mention any major environmental health effects except harbour and food for pest animals.
(a) food/shelter 1.0 Major negative effect
(b) fire regime 0.0 Minor or no effect
(c) altered nutrient levels 0.0 Minor or no effect
(d) soil salinity 0.0 Minor or no effect
(e) soil stability 0.0 Minor or no effect
(f) soil water table 0.0 Minor or no effect
Total 5.5   
Potential distribution Total   
Q1. Within the geographic area being considered, what is the percentage area of land use that is suitable for the weed? 8.0 60-80% of land use Estimate (based on Parsons and Cuthbertson (2001) previous distributions.
Comparative weed risk score 309   
Weed risk category Very high   
Feasibility of coordinated control
Control costs Score      Total   
Q1. How detectable is the weed? 2   In general terms
Parsons and Cuthbertson (2001), pg. 359-368.
(a) Distinguishing features 0 always distinct
(b) Period of year shoot growth visible 2 < 4 months
(c) Height at maturity 1 0.5 - 2 m
(d) Pre-reproductive height in relation to other vegetation 0 above canopy
Q2. What is the general accessibility of known infestations at the optimum time of treatment? 0 high Personal observations although note O. aurantiaca is more restricted to riparian areas.
Q3. How expensive is management of the weed in the first year of targeted control? 2   a. Spot spraying generally (Parsons and Cuthbertson (2001) and Ensbey (2009).
b. Estimate based on spot spraying and digging out.
c. In most situations it would be low - even the physical moving of stems infested with biocontrol agent.
(a) Chemical costs/ha 1 low (< $100/ha)
(b) Labour costs/ha 2 medium ($100-$249/ha)
(c) Equipment costs 1 low
Q4. What is the likely level of participation from landholders/volunteers within the land use at risk? 1.0 medium Personal observations.
Total 4.2   
Persistence Score      Total   
Q1. How effective are targeted management treatments applied to infestations of the weed? 2 medium Estimate based on Parsons and Cuthbertson (2001), Ensbey (2009)
Q2. What is the minimum time period for reproduction of sexual or vegetative propagules? 0 >2 years Parsons and Cuthbertson (2001). This is from seed and shorter times may occur from transplanted segments.
Q3. What is the maximum longevity of sexual or vegetative propagules? ? do not know At least 3 years for segments (inside a lab) but unknown for seeds.
Q4. How likely are new propagules to continue to arrive at control sites, or to start new infestations? 2.0   Parsons and Cuthbertson (2001), pg. 359-368.
(a) Long-distance (>100m) dispersal by natural means 2 frequent
(b) Long-distance (>100m) dispersal by human means  1 occasional
Total 4.5   
Current distribution Total   
Q1. What percentage area of the land use in the geographical area is currently infested by the weed? 1.0 5-10% of land use Estimate based on Botanic Gardens Trust (2010).
Q2. What is the number of infestations, and weed distribution within the geographic area being considered? 2.0 widespread Between restricted and scattered.  Main infestation (H. martinii) between Boggabilla and Keetah area (Tanner 2009).
Total 2.5   
Comparative feasibility of coordinated control score 47
Feasibility of coordinated control category Medium
Management priority category Contain spread
Calculation of overall uncertainty score 11%
Positive impacts Originally introduced into Australia as ornamentals and a feed source for cochineal insects - for red dye. Some jam and jelly making out of fruit. Flowers as a honey source?  Pads have been used as drought feed.
References/Other comments
Botanic Gardens Trust (2010). PlantNET - The Plant Information Network System of Botanic Gardens Trust, Sydney, Australia http://plantnet.rbgsyd.nsw.gov.au (Accessed 17 May 2010).
Ensbey, R. (2009).Noxious and environmental weed control handbook. A guide to weed control in non-crop. aquatic and bushland situations, 4th edition. Industry and Investment NSW, Orange.  pg. 65.
Parsons, W. T. and Cuthbertson, E. G.  (2001). Noxious Weeds of Australia, 2nd edition. CSIRO publishing, Collingwood.  pg. 359-368 - incl. info on O. aurantiaca, O. robusta, O. stricta and O. monacantha (syn. O. vulgaris).

Assessment by Dr Stephen Johnson, Weed ecologist, I&I NSW, 18 May 2010. 

There are a number of information gaps for these species.
Declaration (in part) to continue to support biological control efforts. ...... see below for Opuntia species and biological control agent list.
Species in rough decreasing order of importance, not necessarily geographic distribution (RBG 2010)
Opuntia aurantiaca, Tiger Pear
Opuntia stricta , Common Prickly Pear, Smooth Pest Pear
Opuntia monacantha, Drooping Pear, Smooth Tree Pear
Opuntia spp. sensu I.Telford (1984)
Opuntia elata
Opuntia tomentosa , Velvet Tree Pear
Opuntia elatior
Opuntia robusta, Wheel Cactus, Camuesa
Opuntia humifusa, Creeping Pear
Opuntia streptacantha, Cardona Pear, White-spined Pear, Gracemere Pear, Westwood Pear
Opuntia microdasys, Yellow Bunny Ears, Goldplush, Teddy Bear Cactus
Opuntia schickendantzii
Opuntia ficus-indica, Indian Fig, Spineless Cactus - this species is excluded (it is cultivated and rarely escapes).
Biological control agents (Parsons and Cuthbertson 2001) - general note better and longer period of kill via these agents in Qld than NSW
Opuntia aurantiaca = Predominant agent is tiger pear cochineal insect but also Cactoblastis cactorum and Tucumania tapiacola, and Dactylopius spp.
Opuntia robusta = biological control options are being evaluated (via Australian Weeds Committee)
Opuntia stricta = Cactoblastis cactorum and Dactylopius opuntiae (note: Cactoblastis control has been one of the most successful instances of biological control ever acheived).
Opuntia monacanthus = Predominant agent is monacantha cochineal insect and Dactylopius sp.