Attachment B Weed Control Methodology Table 2015.pdf

Comparison of weed control methodologies
Method

Effectiveness
Environmental Impacts
Human health risks






.

No control
In most situations, no control would result in council’s failure to meet
In some cases native species may co-exist with weed species if the weed
Perceived or actual indirect impact from the growth of weeds:

current level of service.
populations do not dominate to the point of excluding native species
•
Species like privet can trigger hay fever and asthma. 4
Where no weed

suited to the particular habitat. More commonly weeds do out-compete
•
Other species can present a physical hazard (e.g. moth plant sap is
control is
No control can be effective in some parts of the rural road corridor for
and therefore eliminate native plant populations3.
an irritant)5.

undertaken at a
some species. For example, no control of gorse can lead to successful
particular site.
regeneration of native species1.

In a few other situations where erosion control is more important than
species composition, no control of weeds is an effective option2.

Mechanical
Mechanical control methods are not effective ways of killing the entire
Some potential impact on biodiversity, via risk of spreading weeds as
There is a minor risk of injury to the applicator from equipment, or to passers-

plant including the root system, but they trim foliage and can prevent or
fragments can travel on machinery, or re-sprout from fragments on site.7
by (e.g. from stones being flicked up by machinery/line trimmers).
Weed-eating,
reduce seed production and restrict growth. Mechanical control is used

mowing,
most often in combination with other weed control methods in the road
The equipment used for mechanical control may use some fuel.  Fuel
shredding.
corridor (glyphosate, steam and hot water) to increase effectiveness.
consumption and associated carbon emissions have not been quantified.

.
Mechanical control methods must be undertaken between weekly and
monthly, depending on the required level of service, to prevent weeds
from resprouting from stem and root fragments.

Mechanical control is most effective when it is timed well, e.g. before a
plant can set seed6.






Manual
Manual control is not an effective method for most of the hard edges in
This method creates soil disturbance, which can lead to weed invasion12.
There is risk to the applicator through injury via over-exertion during

local parks, nor for much of the road corridor. It can be effective against
Manual control on species that re-sprout from fragments can lead to
operation or injury/illness caused by weed itself (e.g. reaction to sap, or injury
Weed control by
small shrubs and trees and herbaceous weeds in small infestations,
weeds spreading further13.

from appendages such as thorns).  Personal Protective Equipment (PPE),
hand or hand tool.

removing the whole plant8. It is best suited to small plants without
such as long sleeves, pants and gloves, will minimise risk14.
extensive root systems that can be removed without breakage. It is not
recommended for plants with deep underground roots and/or easily
broken roots.9

Most weeds should be removed from the site entirely to avoid fragments
or seed colonising.10 Careful disposal is important for some species (e.g.
those that resprout from fragments, such as tradescantia)11.






1

High Pressure
Steam is not an effective way of killing the entire plant including the root
This method uses 2000L to 3000L of water per day of deployment20. The
Primarily risk to the operator through direct contact with hot water, equipment
Steam
system, but it treats the foliage and can prevent/reduce seed production
environmental impacts of this water consumption will be dictated by
and proximity to traffic.

and restrict growth16. The steam destroys the surface foliage of the
whether the water is sourced from the mains supply or from roof supply,

Application of high
weeds, leaving the roots primarily untreated as the temperature of the
and has not been quantified.
Exposure to the steam is minimal and the heat dissipates quickly once the
pressure steam.
steam decreases (forming liquid water) rapidly upon touching the

steam contacts the weeds or ground. Risks caused by exhaust have also
Includes
ground17.
Similarly the environmental costs from heating the water and powering
potential to cause harm21.
supplementary

the vehicles used for transporting the heated water to the site, will depend

applications of
Steam does not destroy the foliage of some types of weeds (nutgrass
on the sources of the energy being consumed.  If fossil fuels are used
In the road corridor the treatment operator is exposed to moving traffic as
glyphosate or
and kikuyu for example).
there will be associated carbon emissions.  These have not been
they walk alongside the truck. This is minimised by treating the kerb and
mechanical

quantified.
channel from the berm/footpath.
treatment.
Steam must be repeated on a 6 weekly programmed cycle in

combination with or interspersed with mechanical trimming/removal to

Used in
achieve the required level of service to meet required service standard 18.

approximately

700km (9%) of the
To achieve required level of service in this contract area, mechanical
road corridor in
control (weed eaters) is used to remove any weeds in the channel or
north-east urban
growing over the kerb before high pressure steam is applied to the
contract area of
remainder of the plant. High pressure steam is used every second cycle
legacy North
with the intervening cycle being mechanical only.  Weed eaters are also
Shore15.

used to trim the edges of the footpath. Glyphosate-based herbicide is
used to kill the weeds in the channel on the Level 2 roads as the high
pressure steam system (trucks and application system) cannot be used
safely on these roads, with mechanical control (weed eaters) used on the
road berm. Glyphosate is also used to treat specific weeds such as nut
grass.

The current high pressure steam system is too heavy to be accomodated
on park infrastructure such as footpaths and lawns, and is only used in
the road corridor. Application involves large, slow moving vehicles which
are noisy19, so it is limited to non-peak hours in some areas. Traffic
management is required for high volume roads (L2).







Hot water
Hot water treatment is not an effective way of killing the entire plant
This method uses 5000L to 6000L of water per day of deployment26. The
Primarily risk to the operator through direct contact with hot water, equipment
treatment
including the root system, but it treats the foliage and can prevent/reduce
environmental impacts of this water consumption will be dictated by
and proximity to traffic.

seed production and restrict growth23. The hot water destroys the surface
whether the water is sourced from the mains supply or from roof supply,

Application of hot
foliage of the weeds, leaving the roots primarily untreated as the
and has not been quantified.
Exposure to the hot water is minimal and the heat dissipates quickly once it
water.
temperature of the water decreases rapidly upon touching the ground.

contacts the weeds or ground. Risks caused by exhaust have also potential
Supplemented

Similarly the environmental costs from heating the water and powering
to cause harm28.
with mechanical
Hot water does not destroy the foliage of some types of weeds (nutgrass
the vehicles used for transporting the heated water to the site, will depend

removal of larger
and kikuyu for example).
on the sources of the energy being consumed.  If fossil fuels are used
In the road corridor, the treatment operator is at risk to moving traffic as they
weeds.

there will be associated carbon emissions.  These have not been
walk beside the truck on the road.

In this contract area, hot water is applied directly to the weed with no
quantified.
Used in
mechanical control undertaken prior to application of the hot water. Some

approximately
mechanical control is used to trim the edges of the footpaths. No
Thermal treatment can reduce soil micro-organisms and invertebrates27.
735km (9%) of
glyphosate is used in the area where hot water is used.
road corridor in

north-west urban
Control is repeated within an 8 weekly programmed cycle in combination
contract area of
with mechanical trimming/removal. This cycle is not frequent enough to
legacy North
achieve the required level of service24.
Shore22.

The current hot water treatment system (trucks and disposal unit) is too
heavy to be accomodated on park infrastructure such as footpaths and
lawns, and can only be used in the road corridor. Application involves
large, slow moving vehicles which are noisy25, so it is limited to non-peak
hours in some areas. Traffic management is required for high volume
roads (L2).






2

Plant-based
Plant-based herbicides are activated on contact with the foliage of weeds
The vehicles used to apply plant-based herbicides use fossil fuels and
Exposure pathways for occupational and public exposure are managed by
herbicide
and brown off the foliage thus can prevent/reduce seed production and
generate some carbon emissions.  There is concern that some plant-
compliance with standards and procedures.

restrict growth.
based herbicides contain ingredients that contribute to other
Weed control by

environmental effects such as coconut oil. Some of these products are
Meets national health standards when correct application methods and
plant-based
They are usually fast acting32, and they can control some weeds that hot
acidic and can be corrosive. These have not been quantified.
procedures are adhered to.  The EPA has approved Organic Interceptor and
herbicide via foliar
water and steam don’t affect (such as kikuyu)33.

Agpro Bio-safe as a herbicide for use under the Hazardous Substances and
spray.

Direct application of Organic Interceptor may kill beneficial insects and
New Organisms Act (HSNO) Act 1996.
Includes products
Organic Interceptor is a non-selective contact herbicide that causes rapid
bacteria38.
like Organic
dehydration by penetrating green tissue and disrupting normal

Correct application methods are described in the New Zealand Standard on
Interceptor
membrane permeability and cell physiology34.
Bio-Safe is inactivated on contact with the soil and has no residual
the Management of Agrichemicals (NZS 8409:2004), Proposed Auckland
(derived from pine

activity39.
Unitary Plan (part 3.H.4.9.2.2 and .3), and product label as registered by the
essence29) and
Bio-Safe is a non-selective contact herbicide that causes rapid wilting of

EPA. Application must be in accordance with these standards.
Agpro Bio-safe
the leaves and is most effective on actively growing weeds and when

(derived from
applied in hot sunny conditions35.
Agpro Bio-safe carries a health and safety risk to the operators and others
coconut oil30).

who come into contact with the product. The product is corrosive to eye

To meet service standards they must also be used in combination with
tissue and an eye, skin and respiratory irritant. Protective equipment must be
Used in
other methods, and they require more frequent application compared to
worn40.
approximately
glyphosate36. Biosafe is used on a 4 weekly cycle and is supplemented

1049 km (13%) of
with glyphosate. Interceptor is used on a 12 day cycle in combination
Biosafe is a coconut derived fatty acid with a strong, notable odour. This
road corridor in
with mechanical removal.
odour persists for some time after treatment, longer on warm days, and has
legacy Auckland

been the source of complaint from the public.

City and Waiheke
A 2002 trial into weed control methods by the legacy Waitakere City
Island area31.

Council found that Bio-safe was reliably effective only when vegetation is
young especially kikuyu grass. The same trial looked at Organic
Interceptor and glyphosate, and found it the least effective in the trial at
controlling established vegetation especially kikuyu.37







Glyphosate-
Effective tool for controlling annual broadleaf weeds, grasses and other
Approved for use the New Zealand Environmental Protection Agency
Exposure pathways for occupational and public exposure are managed by
based herbicide
monocots affecting hard edges in local parks and found in the road
(EPA).
compliance with standards and procedures.

corridor. It kills the entire plant including its root system42. It requires less

Application of
frequent follow ups than other methods, with an average of three to four
Glyphosate is strongly absorbed into soil and has no residual activity in
Meets national health standards when correct application methods and
approved
treatments a year.
soil46. This reduces the risk of the product being transferred due to rain or
procedures are adhered to.  The EPA has approved glyphosate as a
herbicide through

irrigation, and the risk of the product being taken up by non-target
herbicide for general use under the Hazardous Substances and New
roller ball or foliar
Glyphosate is absorbed through green plant tissue then translocates
plants47. It has a low toxicity to terrestrial animals and wildlife48.
Organisms Act (HSNO) Act 1996.
spray.
throughout the plant including the root system to kill the entire plant 43.

Effectiveness requires weeds to be actively growing and not under
Over use can result in increased resistance in some species, and
Correct application methods are described in the New Zealand Standard on
In approximately
drought stress, with clean foliage for best results.44 Effectiveness is also
therefore effectiveness could decline over time49.
the Management of Agrichemicals (NZS 8409:2004), Proposed Auckland
5500km (69%) of
enhanced when sites are prepared using mechanical weed control

Unitary Plan (part 3.H.4.9.2.2 and .3), and product label as registered by the
the road
methods that reduce or prevent seed production.
The vehicles used to apply glyphosate use fossil fuels and generate some
EPA. Application must be in accordance with these standards.
corridor41.
carbon emissions.  These have not been quantified.  Similarly the life

Nutgrass suffers only a knock-down effect from glyphosate due to the
cycle impacts arising from the manufacture, transport and storage of
There is some community and international expert debate of health risk. In
inability of glyphosate to penetrate the plant’s thick cuticle. However
glyphosate have not been quantified.
March 2015 a World Health Organisation (WHO) sub group, the International
experience shows that when mixed with a wetting agent, glyphosate is
Agency for Research on Cancer (IARC) Working Group, re-classified
effective in killing nutgrass45.

glyphosate as ‘probably carcinogenic to humans (category 2A).50 However,

the EPA has noted that another WHO assessment group, the Joint Meeting
The application rate is quick (using a small left-hand steer vehicle).

on Pesticide Residues, has determined that glyphosate does not pose a

cancer risk to humans51.

There is also some community concern associated with use of glyphosate on

crops and entry into food chain however these potential entry points do not
occur in the road corridor and hard edges of local parks. There is little
evidence of this risk in NZ and appears to be associated with crops that are
genetically modified to be resistant to glyphosate - this means such crops
remain unaffected when glyphosate has been applied. This potential
exposure pathway is not relevant in NZ as no genetically modified crops are
grown commercially in NZ52.

The EPA notes that the current opinion of relevant US, Canada, EU and
Australian government authorities is that glyphosate is safe to be used as a
herbicide. The EPA actively monitors the status of glyphosate and
international developments.  If needed it may initiate a reassessment after
3

reviewing the overseas reports (including WHO, the US EPA and European
Union53.







Biological
Biocontrol is not suited to control weed species typically occurring on
The risk of adverse impacts to the environment is low.
Biocontrol agents rarely pose any risks to humans due to the stringent, pre-
control
hard edges of local parks and many species in the road corridor54.
Before a new biological control agent is released, approval from the EPA
cautionary assessment and registration process.

is needed and all proposed agents are rigorously tested to assess the risk
Used to control
It relies on the weed’s natural enemy being free to grow, and in most
of damage to non-target plants. They are also tested for disease and
suited species in
areas this would contravene the weed control standards of local parks
evaluated for any other unwanted interactions it might have. A
sites across the
and roads.  Biological control might mean that areas are not tidy and
comprehensive cost-benefit analysis is also carried out and the results of
region including
safe, or could cause a nuisance to neighbours or damage to fences.
all these studies are included in an application to the EPA. The
regional parks.

application then goes through a public comment period. 55

Not currently used
All species approved for release must initially come into a containment
in the road
facility until permission to remove them is granted by MPI pending
corridor.
evidence of their correct identity and freedom from any diseases or other

unwanted organisms. 56









1 http://www.openspace.org.nz/Site/Managing_your_covenant/Restoration_information/revegetating_gorse.aspx
2 http://www.doc.govt.nz/documents/science-and-technical/sap243entire.pdf
3 Staff experience and in-field observations
4 https://www.landcareresearch.co.nz/__data/assets/pdf_file/0003/77691/Privet_Biosecurity_factsheet_8.pdf
5 https://www.landcareresearch.co.nz/__data/assets/pdf_file/0007/77911/Ecology_pest_status_moth_plant_Araujia_hortorum.pdf
6 Tu,Hurd & Randall, 2001. Weed Control Methods Handbook: Tools & Techniques for Use in Natural Areas.
7 Tu et al, 2001. Weed Control Methods Handbook: Tools & Techniques for Use in Natural Areas
8 http://www.weedbusters.org.nz/weed-information/controlling-weeds/controlling-pest-herbs-ground-covers
9 Tu et al, 2001. Weed Control Methods Handbook: Tools & Techniques for Use in Natural Areas
10 http://www.nzpcn.org.nz/page.aspx?conservation_habitat_protection_weed_control
11 Auckland Regional Council Weed Control Manual 2008
12 https://www.landcareresearch.co.nz/__data/assets/pdf_file/0018/39042/weed_management_handout.pdf.
13 Auckland Regional Council Weed Control Manual 2008
14 Tu et al, 2001. Weed Control Methods Handbook: Tools & Techniques for Use in Natural Areas
15 Distance provided by Auckland Transport
16 Staff experience and in-field observations
17 Staff experience and in-field observations
18 http://www.regional.org.au/au/asa/1998/6/315hewitt.htm
19 Auckland Transport and their contractors receive complaints from neighbours due to the high noise level during control work using this method – this has resulted in limited hours for operations in residential areas
20 Staff experience and in-field observations
4

21 Diesel engine exhaust is a category 1 carcinogen (Carcinogenic to humans) and petrol engine exhaust is a category 2B carcinogen (Possibly carcinogenic to human); Agents Classified by the IARC Monographs, Volumes 1–112 and
http://monographs.iarc.fr/ENG/Classification
22 Distance provided by Auckland Transport
23 Staff experience and in-field observations
24 B. De Cauwer et al, Efficacy and reduced fuel use for hot water weed control on pavements, Weed Research, 55(2), 195, 2015.
25 Auckland Transport and their contractors receive complaints from neighbours due to the high noise levels during control work using this method – this has resulted in limited hours for operations in residential areas
26 Staff experience and in-field observations
27 http://eap.mcgill.ca/MagRack/JPR/JPR_27.htm
28 Diesel engine exhaust is a category 1 carcinogen (Carcinogenic to humans) and petrol engine exhaust is a category 2B carcinogen (Possibly carcinogenic to human); Agents Classified by the IARC Monographs, Volumes 1–112 and
http://monographs.iarc.fr/ENG/Classification
29 http://www.nzpps.org/journal/55/nzpp_552070.pdf
30 Agpro Bio-safe MSDS
31 Distance provided by Auckland Transport
32 http://www.nzpps.org/journal/52/nzpp_520010.pdf
33 http://www.waitakere.govt.nz/abtcnl/ct/pdf/envrmntl/110602ag.pdf p.51
34 New Zealand Novachem Agrichemical Manual, 2013
35 New Zealand Novachem Agrichemical Manual, 2013
36 http://www.nzpps.org/journal/58/nzpp_581570.pdf
37 http://www.waitakere.govt.nz/abtcnl/ct/pdf/envrmntl/110602ag.pdf p.47
38 New Zealand Novachem Agrichemical Manual, 2013
39 New Zealand Novachem Agrichemical Manual, 2013
40 Agpro Bio-safe MSDS
41 Distance provided by Auckland Transport
42 New Zealand Novachem Agrichemical Manual, 2013
43 New Zealand Novachem Agrichemical Manual, 2013
44 New Zealand Novachem Agrichemical Manual, 2013
45 Graeme Bourdot, AgResearch, Auckland Council Weed Management Workshop 18 June 2015.
46 New Zealand Novachem Agrichemical Manual 2013
47 Glyphosate 360 Material Safety Data Sheet (MSDS)
48 New Zealand Novachem Agrichemical Manual, 2013
49 http://weedscience.org/summary/resistbyactive.aspx
50 IARC Monographs Volume 112: evaluation of five organophosphate insecticides and herbicides
51 http://www.epa.govt.nz/hazardous-substances/pop_hs_topics/glyphosate_learn/Pages/Glyphosate_regulation.aspx
52 http://www.foodsmart.govt.nz/whats-in-our-food/genetically-modifed-food/overview/
53 http://www.epa.govt.nz/hazardous-substances/pop_hs_topics/glyphosate_learn/Pages/Glyphosate_regulation.aspx
54 Staff experience and observations
55 http://www.landcareresearch.co.nz/science/portfolios/managing-invasives/weeds/biocontrol/education/biocontrol-information/biocontrol-safety
56 http://www.landcareresearch.co.nz/science/plants-animals-fungi/plants/weeds/biocontrol/approvals .
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