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) Toxicodendron succedaneum
Weed (Common name) Rhus tree
Region All of NSW
Management area Areas around settlement
Landuse 5.4 Residential
Assumptions Rhus tree, Anacardiaceae. Standard weed management is variable. Tree weeds are very rarely managed despite many tools being available. Density in land use - low (planted).
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' - possibly requires some disturbance - see Parsons and Cuthbertson (2001), pg 165-166.
Q2. What is the weed's tolerance to average weed management practices in the land use? 3.0 95% + weeds survive common management Not seen as a weed unless people are alerted to it.
Q3. What is the reproductive ability of the weed in the land use? 2.0   a. Parsons and Cuthbertson (2001), pg. 166 - seed formed in the third year after planting.
b. Not mentioned by references but note Figure 1 of Oosterhout et al. (2010)
c. Parsons and Cuthbertson (2001), pg. 166 - suckering assumed to be root suckering.
(a) Time to seeding 1.0 >1-3 yrs  
(b) Annual seed production 2.0 High  
(c) Vegetative reproduction 1.0 Infrequent  
Q4. How likely is long-distance dispersal (>100m) by natural means? 2.0   Parsons and Cuthbertson (2001), pg. 166.
Water and wind not mentioned and assumed not to occur.
(a) Flying animals 2.0 Common  
(b) Other wild animals 2.0 Common  
(c) Water 0.0 Unlikely  
(d) Wind 0.0 Unlikely  
Q5. How likely is long-distance dispersal (>100 m) by human means? 1.0   Deliberate spread via nursery sales in Australia is now very unlikely.
Parsons and Cuthbertson (2001), pg. 166 - occassional spread in soil.
Deliberate spread not mentioned and is now probably occasional to rare.
(a) Deliberate spread by people 0.0 Unlikely  
(b) Accidentally by people and vehicles 0.0 Unlikely  
(c) Contaminated produce 1.0 Occasional  
(d) Domestic/farm animals 0.0 Unlikely  
Total 6.3   
ImpactsScore     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? 0.0 No reduction No reduction mentioned by references.
Q4. What is the weed's potential to restrict the physical movement of people, animals, vehicles, machinery and/or water? 0.0 None Parsons and Cuthbertson (2001), pg. 165-166.
Q5. What is the weed's potential to negatively affect the health of animals and/or people? 2.0 Medium Best fits medium (although toxicity is the reason why it is declared) Parsons and Cuthbertson (2001), pg. 166 except deaths would probably not occur.
Q6. Does the weed have major positive or negative effects on environmental health? 0.0   References do not mention any major environmental health effect.
(a) food/shelter 0.0 Minor or no 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 2.9   
Potential distribution Total   
Q1. Within the geographic area being considered, what is the percentage area of land use that is suitable for the weed? 2.0 10-20% of land use Estimate - adaptable to a wide range of soil types although very little recorded as naturalised (BGT 2010).
Comparative weed risk score 37   
Weed risk category Low   
Feasibility of coordinated control
Control costs Score     Total   
Q1. How detectable is the weed? 1   Parsons and Cuthbertson (2001.
(a) Distinguishing features 1 sometimes distinct  
(b) Period of year shoot growth visible 0 > 8 months  
(c) Height at maturity 0 > 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.
Q3. How expensive is management of the weed in the first year of targeted control? 2   If stem injection used (costs for mechanical removal would be higher but generally very few would need to be removed so total cost would be low). Oosetrhout et al. (2010) and Ensbey (2009).
(a) Chemical costs/ha 1 low (< $100/ha)  
(b) Labour costs/ha 1 low (< $100/ha)  
(c) Equipment costs 1 low  
Q4. What is the likely level of participation from landholders/volunteers within the land use at risk? 0.0 high Assumption due to toxicity.
Total 2.5   
Persistence Score     Total   
Q1. How effective are targeted management treatments applied to infestations of the weed? ? do not know Do not know' - it is unclear from the references used.
Q2. What is the minimum time period for reproduction of sexual or vegetative propagules? 0 >2 years Parsons and Cuthbertson (2001), pg. 166.
Q3. What is the maximum longevity of sexual or vegetative propagules? 2 > 5 years Oosterhout et al. (2010) mentions many years - surmised to be more than 5.
Q4. How likely are new propagules to continue to arrive at control sites, or to start new infestations? 2.0   Parsons and Cuthbertson (2001).
(a) Long-distance (>100m) dispersal by natural means 2 frequent  
(b) Long-distance (>100m) dispersal by human means  0 rare  
Total 5.0   
Current distribution Total   
Q1. What percentage area of the land use in the geographical area is currently infested by the weed? 0.1 <1% of land use Relatively few plants left in gardens [or that have escaped into bushland near urban areas].
Q2. What is the number of infestations, and weed distribution within the geographic area being considered? 0.0 restricted Continued enforcement of declaration makes this now an uncommon plant.
Total 0.1   
Comparative feasibility of coordinated control score 1
Feasibility of coordinated control category Very High
Management priority category Monitor & Protect priority sites
Calculation of overall uncertainty score 11%
Positive Impacts Originally introduced as an ornamental tree; it has stunning red foliage in Autumn. No longer planted due to toxicity issues. 
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 3 May 2010).
Ensbey, R. (2009). Noxious and environmental weed control handbook, 4th edition. Industry and Investment NSW, Orange. pg. 67.
Oosterhout, E., Monaghan, N. and McMaugh, J. (2010). Rhus. Primefact 994. Industry and Investment NSW, Orange. 4 pp.
Parsons, W. T. and Cuthbertson, E. G. (2001). Noxious Weeds of Australia, 2nd edition. CSIRO publishing, Collingwood. pg. 165-166.

A wider internet search revealed few useful Australian references.

Assessment by Dr Stephen Johnson, Weed ecologist, I&I NSW 3 May 2010.

Sometimes spreads into urban bushland where it is an environmental weed (this risk assessment does not cover this) (Parsons and Cuthbertson, 2001, pg 165).

There are a number of knowledge gaps for this species - reflected by relatively high uncertainty score.