Chilean needle grass

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 declaration of this weed in New South Wales.

Weed (Scientific name) Nassella neesiana
Weed (Common name) Chilean needle grass
Region NSW
Management Area Tablelands and slopes
Landuse 3.2 Grazing modified
Assumptions also Conservation & natural environments
Weed Risk
Invasiveness Score      Total Answers Source and comments
Q1. What is the ability of the weed to establish amongst existing plants? 1.0 Seedlings establish after moderate disturbance see references at end
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  
Q3. What is the reproductive ability of the weed in the land use? 2.0   
(a) Time to seeding 2.0 1 year or less
(b) Annual seed production 2.0 High
(c) Vegetative reproduction 0.0 None
Q4. How likely is long-distance dispersal (>100m) by natural means? 2.0   
(a) Flying animals 1.0 Occasional
(b) Other wild animals 2.0 Common
(c) Water 1.0 Occasional
(d) Wind 0.0 Unlikely
Q5. How likely is long-distance dispersal (>100 m) by human means? 2.0   
(a) Deliberate spread by people 0.0 Unlikely
(b) Accidentally by people and vehicles 2.0 Common
(c) Contaminated produce 1.0 Occasional
(d) Domestic/farm animals 2.0 Common
Total 6.0   
Impacts Score      Total   
Q1. Does the weed reduce the establishment of desired plants? 2.0 10 - 50% reduction  
Q2. Does the weed reduce the yield or amount of desired vegetation? 3.0 25 - 50% reduction  
Q3. Does the weed reduce the quality of products, diversity or services available from the land use? 2.0 Medium  
Q4. What is the weed's potential to restrict the physical movement of people, animals, vehicles, machinery and/or water? 1.0 Low  
Q5. What is the weed's potential to negatively affect the health of animals and/or people? 1.0 Low  
Q6. Does the weed have major positive or negative effects on environmental health? 1.0   
(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 5.3   
Potential Distribution Total   
Q1. Within the geographic area being considered, what is the percentage area of land use that is suitable for the weed? 4.0 20-40% of land use  
Comparative weed risk score 126   
Weed risk category High   
Feasibility of coordinated control
Control Costs Score      Total   
Q1. How detectable is the weed? 2   
(a) Distinguishing features 2 non-descript
(b) Period of year shoot growth visible 0 > 8 months
(c) Height at maturity 1 0.5 - 2 m
(d) Pre-reproductive height in relation to other vegetation 1 similar height
Q2. What is the general accessibility of known infestations at the optimum time of treatment? 1 medium  
Q3. How expensive is management of the weed in the first year of targeted control? 4   
(a) Chemical costs/ha 3 high ($250-$500/ha)
(b) Labour costs/ha 3 high ($250-$500/ha)
(c) Equipment costs 2 medium
Q4. What is the likely level of participation from landholders/volunteers within the land use at risk? 1.0 medium  
Total 6.7   
Persistence Score          Total   
Q1. How effective are targeted management treatments applied to infestations of the weed? 3 low  
Q2. What is the minimum time period for reproduction of sexual or vegetative propagules? 2 6-12 months  
Q3. What is the maximum longevity of sexual or vegetative propagules? 2 > 5 years  
Q4. How likely are new propagules to continue to arrive at control sites, or to start new infestations? 1.0   
(a) Long-distance (>100m) dispersal by natural means 1 occasional
(b) Long-distance (>100m) dispersal by human means 0 rare
Total 7.3   
Current distribution Total   
Q1. What percentage area of the land use in the geographical area is currently infested by the weed? 0.5 1-5% of land use  
Q2. What is the number of infestations, and weed distribution within the geographic area being considered? 1.0 scattered  
Total 1.3   
Comparative feasibility of coordinated control score 61
Feasibility of coordinated control category Low
Management priority category Manage weed
Calculation of overall uncertainty score 0%
Response Submit Assessment
Positive Impacts  
References/Other comments
PlantNET (2009). Flora Online module of PlantNET. Royal Botanic Gardens and Domain Trust, Sydney. Online at
Storrie, A.M. and Lowien, J.C. (2003). Chilean needle grass. Agnote DPI 194, 3rd edition. NSW Agriculture. 5pp.
Weed Management CRC (2003). Chilean needle grass (Nassella neesiana) Weed Management Guide. 6pp.