Download Update: Invasive Plants of Increasing Concern

UPDATE:
INVASIVE PLANTS
OF INCREASING
CONCERN
Antonio DiTommaso
Department of Crop and Soil Sciences
Cornell University ([email protected])
WHY WORRY?
 Invasive plants estimated to cost the U.S. economy $40
billion/year; $26.4 billion due to cropland weeds
 Second leading cause of species endangerment and recent
extinctions
 Climate change will result in different weed flora
 Negatively impact human health
 Damage human enterprises and ecosystems
 Expanding air travel, more ports of entry
 Improved access to foreign ecosystems
 Decreased diversification in production systems
HOW ARE NON-INDIGENOUS
INVASIVE PESTS INTRODUCED?
 Accidental versus Deliberate – proportion varies among
taxonomic groups
 Few invasive microorganisms deliberately introduced
 Majority of invasive insects or marine invertebrates
likely accidentally introduced
 Most invasive vertebrates especially fish, mammals,
and birds have been deliberately introduced
 Most invasive plants have been deliberately introduced
(horticultural industry)
Pest Increase Over Time & Control Potential
(4)
Local control and
management only
Public awareness
typically begins
Control Costs
Acres Infested
Prevention
or
Eradication
simple
Introduction
(3)
Eradication unlikely,
intense effort required
(2)
Eradication
feasible
(1)
Detection
Absent or off-site
few locations
Many
locations
Time
At or near biological potential
PLANT INVADERS TO
WATCH FOR!
 Mile-a-minute (Polygonum perforliatum)
 Japanese knotweed (Polygonum cuspidatum)
 Spotted knapweed (Centauria stoebe ssp.
micranthos)
 Pale and black swallow-worts; (Vincetoxicum
rossicum & V. nigrum)
 Wild parsnip (Pastinaca sativa)
 Common reed (Phragmites australis)
 Japanese stiltgrass (Microstegium viminieum)
Spotted Knapweed (Centauria stoebe ssp. micranthos)
•
European plant introduced in the late
19th century to Pacific Northwest,
possibly through contaminated clover
and alfalfa seed.
•
Found in fields, pastures, roadsides,
waste spaces and other open areas.
•
Also known as Centaurea maculosa,
Centaurea biebersteinii.
Description
•
Herbaceous biennial or short-lived perennial.
•
Not shade tolerant.
•
First-year rosette has hairy, grayish, and
pinnately lobed leaves up to 6 inches long.
•
Mature plants stand 1-3 feet. Leaves of mature
plant are alternate, pinnately lobed on lower
stem and lance-shaped on upper stem. Stems are
ribbed and hairy.
•
Develops a long taproot.
Reproduction
• Blooms from mid to late summer.
• Flowers are pink to purple and thistlelike, with stiff, black tipped involucre
bracts. Flowers grow singly or in
clusters.
• Seeds are achenes, with short bristly
pappus at base. Wind dispersed.
• An individual plant can produce up to
2,000 seeds, which may persist in the
seed bank for over 8 years.
Similar Species
Brown (Centaurea jacea) and black (Centaurea
nigra) knapweed are also present in NY. The
leaves of these knapweeds are entire or with
only shallow lobes and the involucre bracts
have long fringes.
Brown knapweed
Black knapweed
Similar Species
Meadow (Centaurea pratensis) knapweed is
also present in NY. A hybrid of black and
brown knapweeds. Foliage coarse and tough.
Blooms in midsummer to fall. Grows from
woody root crown and up to 3.5 ft tall. Lower
leaves are long-stalked, upper leaves have no
stalk. Stems are many-branched and tipped by
a solitary flower head up to one inch wide.
Flower heads are pink to reddish purple, oval
or almost globe-shaped. A key identifying
feature is the fringed bracts on the flower
head. However, because meadow knapweed is
a hybrid, it traits can vary. Also be referred to
as C. nigrescens, C. x moncktonii, C. debeauxii
ssp. thuillieri, and C. jacea x nigra.
Impacts
•
Low palatability of mature plants to cattle can lead to overgrazing of other plant species in
pastures, lowering community diversity and reducing land value.
•
Dense stands of dead, dried knapweed stems can impede access to forage.
•
Displacement of native species and decreased diversity in natural areas. But late season
nectar source for bees.
•
Increased soil erosion, particularly if spotted knapweed displaces native and naturalized
grasses.
•
Spotted knapweed produces the allelochemicals (±)-catechin and cnicin, although the extent
to which they affect native plants is uncertain.
Management
Mechanical
Chemical
• Does not persist under
annual cultivation.
• Herbicides can be useful in
controlling new invasions.
• Mowing at flowering can
reduce seed production.
• Clopyralid, dicamba,
picloram, and 2,4-D effective
at controlling spotted
knapweed in rangeland.
• Increase grazing stocking
rates. Fertlize/lime fields
• Young plants and spring
growth may be vulnerable
to browsing by some
livestock, particularly
sheep.
Biological
•
•
•
•
• Scope of infestation and
persistence in seed bank may
make large scale herbicide
use impractical.
Thirteen specialist insects have been released in North America.
Eight feed on flowers, five on roots.
Several released in NY.
Success has been limited, possibly due to complex phylogeny of
knapweed species.
Wild Parsnip (Pastinaca sativa)
• Wild form of the cultivated parsnip.
Native to Europe.
• Common along roadsides, railroads,
field edges, and in waste areas and
other disturbed sites. Can invade
natural areas.
• Much more widespread in NY than
map suggests.
Description
• Short lived monocarpic perennial.
• During first year forms a rosette and
thick, yellow-white taproot that can
reach up to 1.5 m in depth.
• Mature plant generally 2-5 feet tall.
• Stem branching, grooved, sparsely
haired, and hollow.
• Leaves alternate, pinnately
compound, toothed and clasping.
Stem and basal leaves similar.
Reproduction
• Flowers from late spring to early summer.
Some individuals may flower later in the
season.
• Flowers are small, 5-petaled, yellow, and
borne in large (3-8 inch) compound
umbels.
• Fruit is dry, flattened, winged, schizocarp
that splits into two seeds.
• Dispersal is primarily by
wind.
Similar Species - Golden Alexanders
(Zizia aurea)
Impacts
• Wild parsnip sap contains furanocoumarins, which cause
phytophotodermatitis when skin is exposed both the sap and UV
radiation. Symptoms include inflammation, redness, burning and
blistering.
• Livestock that consume wild parsnip are vulnerable to
phytophotodermatitis.
• May displace native plants like Canada goldenrod (Solidago
canadensis) in old fields and meadows.
Management
Mechanical
• Individual plants can be controlled by cutting the stem
beneath the basal leaves or by hand pulling.
• Seeds do not survive long in seed bank, so methods that
reduce seed production may be most effective.
• Timing of mowing is essential. Mow when flower stalks
begin to form to minimize seed production.
• In natural areas, succession may be effective control.
•
Whether mowing or hand weeding, proper PPE is essential.
Chemical
• Herbicides most effective on first year rosettes.
Thank You!
https://weedecology.css.cornell.edu/