| Overview of Control Methods |
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| Prepared by Michael Van Clef, Ph.D., Ecological Solutions,
LLC |
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Method Name |
Method Type(s) |
Typical Herbicide Concentrations |
Target Type(s) |
Basic Technique |
Pros |
Cons |
Notes |
| biological control |
Biological Control |
N/A |
few selected species |
Release of approved biological control agents that attack
only target species |
Method can provide effective control and is cost effective |
There are no widespread species in Washington Township
with an available biological control agent. |
A biological control agent for garlic mustard is under
development and may be ready for release in the near future. |
| basal bark |
Chemical Control |
20 - 25% |
woody species |
Application of herbicide within a 6-12 inch band around
entire stem approximately 12 inches above base of plant |
Method provides effective control and is cost effective |
Some suggested oil diluents are not environmentally friendly,
but vegetable or citrus oils with triclopyr can be effective (Rathfon
2006) |
Herbicide application is performed using a backpack sprayer.
Method used for woody stems ≤ 6" in diameter. This method should
be considered an important control technique. |
| foliar spray |
Chemical Control |
1-3% |
Any plant less than 4 feet tall |
Application of herbicide using a backpack sprayer to
wet all leaves |
Method provides effective control and is cost effective |
Method has potential to injure non-target species and
cannot be used on taller plants due to increased risk to applicator
and non-target species (i.e., spraying upward increases risk of drift);
Method can be sensitive to weather conditions (e.g., heat may dry spray
before effective absorption) |
Foliar applications generally include use of a backpack
sprayer (Recommend use of Thinvert system 1 ). Some foliar application
methods include wipe-on applications (e.g., "bloody glove"),
but these methods are not recommended because they are extremely time
consuming and increase likelihood of exposure to the applicator. The
use of boom applications is generally not recommended, but may be useful
in the establishment of native warm season grasses where all existing
vegetation must be removed prior to seeding. |
| pre-emergent spray |
Chemical Control |
1-3% |
herbaceous species |
Application of herbicide to prevent seed germination |
Method can provide effective control |
Requires a broad application in areas known or suspected
to contain invasive species; Timing of application can vary between
years for targeted species; Supresses germination of all species |
This method is not generally recommended. |
| hack-and-squirt |
Chemical & Mechanical Control |
20 - 25% |
woody species |
Make downward cuts with a hand axe (one cut per inch
of diamter) and apply herbicide to cuts |
Method provides effective control and is cost effective;
Volunteers can assist with stem cutting |
Stem cutting may be difficult for thick-barked plants |
Herbicide applied with squirt bottle or paint brush.
Herbicide should be applied immediately after cutting. |
| stem injection |
Chemical & Mechanical Control |
20 - 25% |
woody species |
E-Z-Ject Lance loaded with herbicide pellets |
Method provides effective control |
Equipment is difficult to operate under field conditions;
Injection for thick-barked trees requires signifcant force; Equipment
is expensive |
A modified approach using a drill and manual insertion
of herbicide may be more practical. This method is not generally recommended. |
| cut stump |
Chemical & Mechanical Control |
20 - 25% |
woody species |
Cutting stems just above ground level followed by targeted
application of herbicide to cut stems |
Method provides effective control; Volunteers can assist
with stem cutting |
Mechanical removal of stems is very time consuming |
Cutting is performed by loppers, handsaws or chainsaws
depending upon size of stems. Herbicide applied with a squirt bottle,
paint brush or backpack sprayer. Herbicide should be applied immediately
after cutting. |
| prescribed fire |
Cultural Control |
N/A |
many species |
Should follow a site-specific Prescribed Burning Plan
that is part of a comprehensive Grassland Management Plan |
Method provides effective control and is cost effective |
Requires highly trained personnel; Insurance requirements
may restrict application to an outside contractor; Requires public
outreach to neighbors and public officials |
Prescribed fire is most effective for grasslands with
dense stands of native warm season grasses that provide ample fuel
to eliminate woody seedlings; Prescribed fire may be utilized to remove
dense thatch before application of herbicides (e.g., common reed, reed
canary grass) in wetland habitats. The effectiveness of presribed fire
to control invasive species in forest habitats is currently uncertain. |
| prescribed grazing |
Cultural Control |
N/A |
many species |
Rotational system using multiple livestock species; Should
follow a site-specific Presribed Grazing Plan that is part of a comprehensive
Grassland Management Plan |
Method may be effective; Method can be assisted by volunteers |
Method requires significant expertise in selection of
livestock species, density of animals per unit area and timing of grazing;
Method requires installation of fencing; Method may spread some invasive
species through feces; Trampling of vegetation may encourage invasive
species |
Implementation will require consultation with experts
in the use of livestock for the purpose of eliminating invasive species;
Method may be considered for shrub control in forest settings if native
species are currently absent |
| soil tilling |
Cultural Control |
N/A |
herbaceous species and woody seedlings |
Turning of soil using typical farm equipment |
Method may provide effective control and is cost effective |
Method destroys native species along with invasive species;
Method may increase invasive species through extensive soil disturbance |
This is an extreme method with limited use in natural
areas. Successive tilling events may be used to exhaust weed seed bank
prior to re-planting pollinator meadows. |
| mulching |
Cultural Control |
N/A |
herbaceous species |
Application of a thick layer (3-4 inches) of organic
materials |
Method is effective for herbaceous species within cultivated
garden beds or roadsides; Method can be assisted by volunteers |
Method is not practical in natural areas where vehicle
access is limited |
Only effective on species with small seeds or weakly
growing plants that cannot germinate/grow through the mulch. Japanese
stiltgrass and garlic mustard are sensitive to heavy mulching. |
| solarization |
Cultural Control |
N/A |
herbaceous species |
Application of plastic sheeting over infested areas |
Method may be effective in some situations; Method can
be assisted by volunteers |
Method may alter soil chemistry and biology more significantly
than herbicides |
Plastic sheeting increases soil temperature to kill seeds
and plants. This method is not generally recommended. |
| girdling |
Mechanical Control (may be combined with Chemical Control) |
N/A |
woody species |
Cutting and removing a ≥ 3 inch band of bark from
a trunk |
Method can provide effective control; Method can be assisted
by volunteers |
Method may be ineffective on species with re-sprouting
ability; Method is time consuming and difficult for thick-barked species;
Method cannot be utilized where the risk of standing dead trees is
unacceptable |
Method may be combined with chemical control (i.e., apply
herbicide to girdled area); Do not attempt on species such as black
locust, tree-of-heaven or Japanese angelica tree, which will vigorously
re-sprout multiple stems in response to girdling (hack-and-squirt may
be effective on these species) |
| mowing |
Mechanical Control |
N/A |
many species |
Cutting tops of plants using a mower, brush cutter or
weed whacker |
Method may be used as a pre-treatment for herbicide application
to cut stumps or foliar applications to re-sprouts using a backpack
sprayer |
Method is ineffective for most species because of re-sprouting
ability |
Japanese stiltgrass can sustain itself as a "lawn" by
producing seeds on plants that are two inches or smaller |
| pulling |
Mechanical Control |
N/A |
small woody plants and herbaceous species |
Removal of entire plant by hand or use of specialized
tools such as a "Weed Wrench" |
Method can provide effective control; Method can be performed
by volunteers |
Method is extremely time consuming and ineffective when
root system cannot be completely removed; Method creates soil disturbance
that stimulates germination of invasive species such as garlic mustard
and Japanese stiltgrass |
This method should only be considered on a limited basis. |
| hot foam spray |
Mechanical Control |
N/A |
herbaceous species |
Rental of Waipuna Hot Foam System |
No herbicides are required |
System rental cost is $700/month with a two-year lease
commitment and there are other related equipment costs; system can
only be used within 200 feet of a vehicle that carries the specialized
hot foam generator, many herbaceous plants require multiple treatments |
This is an innovative system, but has significant financial
and practical limitations. This method is not generally recommended. |
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| 1 Thinvert system involves use of specialized
spray nozzles combined with a thin invert emulsion spray fluid (instead
of using water to mix with herbicides). The primary advantage is less
herbicide drift to non-target plants and an overall lower volume of
spray required to treat a given area. Although the system is more expensive
than typical spray systems, it is ultimately cost effective because
of labor-savings generated through reduction of re-filling of sprayers. |
