Control Them Beyond Where We Cut, Pull and Spray
Controls of non-native invasive plant species
tool kit for successful control of non-native invasive
plants includes preventing new invasive species from coming
in from Europe, Asia, and other continents; manual removal,
the use of carefully targeted herbicides, and host specific
biological controls. Classical biological control involves
the importation and release of host-specific natural enemies
to help regulate pest populations. This strategy is usually
used for invasive non-native species that lack effective
natural enemies in the region where they have been introduced.
In order to avoid direct damage to non-target species,
biological control agents must be highly host specific.
Agents are brought over after being tested or reviewed
for host specificity in their native range and then tested
in quarantine conditions in the United States. They are
only approved for release if testing indicates a very
low likelihood of non-target effects, as determined by
the Technical Advisory Group for Biological Control Agents
of Weeds (TAG), a group of experts that report to USDA-APHIS.
Effectiveness of classical biological control can vary,
but of 49 invasive plant projects considered in a recent
review (Van Driesche et al. 2010), 27% (13) achieved complete
control, 33% (16) provided partial control, and 49% (24)
were still in progress. The problem of bio-controls harming
non-target organisms was reported to be only about 3%
as frequent as before the new rules of proving host specificity
went into effect.
two of the most important invasive plant species requiring
control in Mid-Atlantic natural areas, purple loosestrife
(Lythrum salicaria), and mile-a-minute weed (Persicaria
perfoliata), one or more host-specific insect species
have been tested and received permits for release. Three
other invasive plant species have had extensive studies
conducted on host-specific insects, with petitions for
release submitted to TAG, but with proposed releases still
under review (TAG Petitions, 2013). These plant species
and associated insects are garlic mustard (Alliaria
petiolata), the crown-mining weevil (Ceutorhynchus
scrobicollis); Japanese knotweed (Fallopia japonica),
the psyllid Aphalara itadori; and tree-of-heaven
(Ailanthus altissima), the weevil Eucryptorrhynchus
For some species, biocontrols may already exist in the
U.S. in the form of native insects and pathogens that
have adapted to the invasive species over time, or non-native
species that were accidentally introduced.
updates with references for 18 non-native terrestrial
and aquatic invasive species are available in the MAIPC
Biocontrol Work Group document http://www.maipc.org/MAIPC_BiocontrolWG_Dec18.doc
One example is.
European Water Chestnut
European water chestnut (Trapa natans) is an
invasive aquatic plant native to Europe and Asia. It was
first observed in the United States in Massachusetts in
the late 1800s. Its current distribution is the mid-Atlantic
and northeastern U.S., with the most serious problems
being reported for the Connecticut River valley, Lake
Champlain region, Hudson River, Potomac River and the
upper Delaware River (Swearingen et al. 2010). This species
can form dense floating mats, and its sharp fruits can
cause painful wounds, making control efforts a challenge.
The most promising species for biological control is Galerucella
birmanica, a leaf beetle (Ding et al. 2006, 2007), but
so far no petitions have been submitted to TAG.
For more information on this and other invasive species
in Maryland, visit the Maryland Invasive Species Council