Transcript Lepidium latifolium: A Case Study

Lepidium latifolium: A
Case Study
What is Lepidium Latifolium?:
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Semi-woody plant that grows in
dense masses of erect stems
Grows 1-3ft tall, but can grow up to
8ft tall in wet growing conditions
Leaves and stems are waxy
Leaves are alternate with toothed to
smooth blades (0.5 – 1.0 inches
wide)
Flowers are a brilliant white, arranged
in dense panicles in clusters of 6 to8.
(Young 1995)
Common Names….
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Whitetop
Tall Whitetop
Broadleaf Peppergrass
Broadleaf Pepperwort
Perennial Pepperwort
Pepperwort
Virginia Pepperweed
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USDA (2008)
Where is Lepidium latifolium from and where has it
naturalized to?
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Native to Eurasia and
Northern Africa
Figure 1: Distribution of Lep. L.
throughout North America. (USDA, 2008)
Believed to have been
accidentally introduced to
North America as a
contaminant in Sugar Beet
seed (Young et al., 2005)
Has become naturalized in
Australia, Mexico, Canada
and the United States
Within the U.S. Lepidium
latifolium has been
declared a noxious weed in
13 states and by the
Bureau of Land
Management (USDA,
2008)
Why is it considered invasive?
Likes to establish near wetlands,
riverbanks, riparian areas and flood plains
(Renz et al, 2004)
 Forms extremely dense clonal
monocultures
 Has a tendency to out grow pre-existing
vegetation by:
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– Consuming available nutrients and moisture
– Forming a dense canopy where light cannot
penetrate
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Incredibly difficult to get rid of!
(Donaldson, 1997; Young et al., 1997)
What makes it invasive?
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There are several properties that make perennial
pepperweed a fierce competitor
– Has high rate of dispersion
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Reproduces by both seed and stoloniferous rhizomes; these
are generally carried by water to vulnerable downstream
areas (Whitson et al., 1992; Donaldson, 1997)
Produces 15 billion seeds/ha; spread of seeds is facilitated
by wind, animals, humans and vehicles (Eiswerth et al.,
2005)
– Has an extensive root system
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Hypothesized that deep root system is what allows
perennial peperweed to access water and gain a
competitve advantage agiainst natives (Qualls et al., in
prep)
– Has high phenotypic plasticity for survival
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Can tolerate shade, sun, and extensive flooding (Qualls et
al., in prep)
Ecological Effects:
 Influences
soil properties and
elemental cycling
– Blank et al., 2002
 Alters
biogeochemical cycling so that
affected sub soils are ameliorated
– Blank and Young, 2002
Ecological Effects: Perennial pepperweed
Influences soil properties and elemental cycling
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In an experiment by Blank et.al. (2002) the effect of soil
nutrient depletion on the growth of and competition
between perennial pepperweed and Bromus tectorum was
examined
Species were grown individually and in combination
When the perennial pepperweed flowered, the roots and
aboveground mass of both species were harvested.
Soils were then homogenized.
Soil was re-planted with the same species
This cycle was repeated for 3 growth cycles.
Ecological Effects: Perennial pepperweed
Influences soil properties and elemental cycling
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(Blank et al., 2002)
The Results:
– After 3 growth cycles the boveground mass of the
perennial pepperweed decreased significantly, and the
growth potential of the perennial pepperweed was
surpassed by that of the Bromus tectorum
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The Conclusion:
– The data suggests that, as nutrients are biocycled to the
upper layers of the soil, the monoculture stands of
pepperweed may become nutrient limited and outcompeted by plants with greater root densities.
Ecological Effects: Perennial pepperweed
Influences soil properties and elemental cycling
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Figure 2: Root/Shoot
ratios of Bromus Tectorum
and Lepidium latifolium
after each of three growth
cycles (Blank et al., 2002).
Ecological Effects: Perennial pepperweed alters biogeochemical
cycling so that affected sub soils are ameliorated
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(Blank and Young, 2002)
Tested the hypothesis that perennial pepperweed
“alters biogeochemical cycling relative to preexisting vegetation such that sodium affected
sub-soils are ameliorated”
Cycling and distribution of different elements
were monitored for four years in sites that were
both invaded with perennial pepperweed and
sites that were not invaded but contained
Elytrigia elongata.
Ecological Effects: Perennial pepperweed alters
biogeochemical cycling so that affected sub soils are
ameliorated
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(Blank and Young, 2002)
The Results:
– Perennial pepperweed had significantly greater
concentrations of of C, Ca, Mg, K, and S in above ground
tissue that Elytrigia elongata
– Perennial pepperweed was increasing the solubility of
Ca2+
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The Conclusion:
– The increased solubility of Ca2+ lowered the ratio of
sodium adsorption to the soil, and ameliorated the soils
by “decreasing dispersion, increasing aggregation [of
sodium] and improving physical properties.
– Once sodic soils are ameliorated they will likely be able
to support a richer and more productive community, if
perennial pepperweed can be controlled.
Ecological Effects: Perennial pepperweed alters
biogeochemical cycling so that affected sub soils are
ameliorated
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Figure 3: Biogeochemical
fluxes of C, Ca, Mg, K, and S
in Elytrigia elongata and
Lepidium latifolium and
calculated SAR (sodium
adsorption ratios). (Blank and
Young, 2002)
Immiscibly displaced
(aqueous-soluble) Mg+2,
Ca+2, Na+, K+, and SO4-2
and sodium adsorption ratio
(SAR) calculated from ID
values, by plant (Lepidium
latifolium community vs
Elytrigia elongata community)
and soil depth. Bars are + 1
standard error.
Control
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Very difficult to control through mechanical
methods
– Deep tap roots, rhizomenous regeneration
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Very difficult to control through Chemical
methods
– Waxy layer of cutin that protects leaves and stems
– Perennial pepperweed generally grows by water. Only
two herbicides are safe for use by water and affective
against broadleaf vegetation
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Glyphosate (N-Phosphonomethylglycine)
2,4-D (2,4-dichlorophenoxy acetic acid)
No existing mechanisms for biological control
Control- tilling and herbicides
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In experiments by Young et al. (1998) control of
perennial pepperweed was examined through use
of tilling and herbicides over wide range of soils,
over a 2 year period.
Results
– Tillage with periodic disking had no permanent affect
– Applications of 2,4-D and Glyphosate had no permanent
affect
– Applications of Chlorsulfuron was effective in destroying
the perennial pepperweed; 3 years after the initial
application, the plants had not re-established
Control – mowing and herbacides
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In a study performed by Renz and
DiTomaso (2004) it was demonstrated
that perennial pepperweed could
potentially be controlled by mowing
followed by an application of Glyphosate
– Mowed plants translocated more glyphosate
from their basal leaves to their below ground
tissue than un-mowed plants
 Mowed
plants accumulated 6.7% of glyphosate
 Unmowed plants only accumulated .38% of
glyphosate
Control – mowing and herbacides
Table 1: Average percent 14C-glyphosate
recovered in various tissues of perennial
pepperweed 48 hours after labeling (Renz et al.,
2004)
Control - Flooding
Study by Qualls et al. (in prep)
 When perennial pepperweed was
subjected to 3 months of flooding, with
water above the plant tops the following
ocurred…
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– Rapid die back of above gound tissue
– 17% of the root stock survived to re-sprout
after the soil was drained
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Conclusion:
– Perennial pepperweed appears to have a wide
range of tolerance for survival
Control- Mowing and grazing by
sheep
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In a study conducted by Allen et al. (2001) Sheep
grazing and mowing were both examined as
methods for the control of perennial pepperweed.
Infested pastures were mowed or grazed for one
season
Results:
– Pastures that had been grazed by sheep had a reduction
in perennial pepperweed of 78%
– Pasures that had been mowed had a reduction of 48%
– These results are contrary to grazing experiments using
goats (Young et.al.,2000)
Control- Mowing and grazing by
sheep
Figure 4: Change in number of perennial pepperweed
plants in mowed and grazed pastures after one season.
(Allen, 2001).
Economic and Social Impacts
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A dynamic cost-benefit analysis for the control of
perennial pepperweed was performed by Eiswerth
et al. (2005)
– Costs and benefits for land that was used solely for
grazing and for land that was used for both grazing and
hay harvest were estimated by analyzing current costs
for weed control (Table 2), estimated future control
costs, future forgone revenues, and by calculating the
standardized benefits and costs for infested land.
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Results:
– On land that is used for grazing only, it would take 15
years for the costs to equal the returns.
– On land that is used for both grazing and hay, it would
take 5-6 years for the costs of control to equal the
returns
Economic and Social Impacts
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Table 2: Predicted costs
for weed control (Eiswerth
et.al. 2005).
Economic and Social Impacts
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Figure 5: Predicted costs and foregone net revenues for infested land. L1, cumulative foregone net
hay harvest and grazing revenue at 30% weed expansion rate; L2, cumulative foregone net hay
harvest and grazing revenue at 15% weed expansion rate; L3, cumulative foregone net grazingonly revenue at 30% expansion rate; L4, cumulative foregone net grazing-only revenue at 15%
expansion rate; C1, cumulative cost to control the infestation at 70% control rate; C2, cumulative
cost to control the infestation at 80% control rate; C3, cumulative cost to control the infestation at
90% control rate (Eiswerth et.al.2005)
Conclusions
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Perennial pepperweed is very difficult to control; at the
moment it is hopeless for eradication
It should have become a top priority for eradication 30 to
40 years ago
May still be possible to thwart the continued spread of
Perennial pepperweed through education, prevention, rapid
response, and diligence in monitoring and treatment
Hopefully an effective bio-control agent will be found!
Or, perennial pepperweed may eventually eradicate itself
through its currently observed patterns of nutrient cycling
However! If I were to recommend a treatment for control,
I would recommend a regiment that consists of grazing by
sheep and mowing for areas that are accessible to
livestock. For areas that are inaccessible by livestock, would
recommend a treatment of mowing/weed-wacking followed
by glyphosate spot application.
References
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Allen JR, Holcombe DW, Hanks DR, Surian M, McFarland M, Bruce LB, Johnson W,
Fernandez G (2001) Effects of sheep grazing and mowing on the control of
perennial pepperweed (Lepidium latifolium). American Society of Animal
Science 52
Blank RR, Young JA (2002) Influence of the exotic invasive crucifer Lepidium latifolium,
on soil properties and elemental cycling. Soil Science167:821-829
Blank RR, Qualls RG, Young JA (2002) Lepidium latifolium: plan nutrient competitionsoil interactions. Biol. Fertile Soils 35:458-464
Birdsall JL, Quimby PC, Svejcar TJ, Young JA (1997) Potential for Biological Control
of Perennial Pepperweed (Lepidium latifolium)
Chen H, Qualls RG, Miller GC (2002) Adaptive responses of Lepidium latifolium to soil
flooding: biomass allocation, aerenchyma formation, adventitious rooting and
ethylene production. Environmental and Experimental Botony 48: 119-128
Donaldson, SG (1997) Flood-Borne Noxious Weeds: Impacts on Riparian Areas and
Wetlands. California Exotic Pest Plant Council; 1997 Symposium Proceedings
Eiswerth ME, Singletary L, Zimmerman JR, Johnson WS (2005) Dynamic Benefit-Cost
analysis for Controlling Perennial Pepperweed (Lepidium latifolium): A Case
Study. Weed Technology 19:237-243
Lipa JJ (1974) Survey and Study of Insects Associated with Cruciferous Plants in Poland
and Surrounding Countries: Final Report. Inst. Of Plant Prot., Lab. Of Biol.
Contr., Miczurina 20, Poznan, Poland, 310pp
Qualls JR, Walker M (In preparation) Competition for Water by Tall Whitetop
References Continued…
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Renz MJ, DiTomaso JM (2004) Mechanism for the enhanced effect of
mowing followed by glyphosate application to re-sprouts of
perennial pepperweed (Lepidium latifolium). Weed Science 52:1423
United States Department of Agriculture (2008) Plants Profile: Lepidium
latifolium.http://plants.usda.gov/java/profile?symbol=LELA2,
November 18, 2008.
Whitson TD, Burrill LC, Dewey SA, Cudney DW, Nelson BE, Lee RD, Parker
R (1992) Weeds of the West. Western Society of Weed
Science. Newark, CA, 630pp
Young, JA (1995) Perennial Pepperweed. Rangelands 17:121-123
Young JA,Palmquist DE, Wotring SO (1997) The invasive nature of
Lepidium latifolium: a review. Plant Invasions: studies from North
America and Europe p. 59-68. Leiden, Netherlands :
Backhuys
Young JA, Palmquist DE, Blank RR (1998) The Ecology and control of
Perennial Pepperweed. Weed Technology 12:402-405
Young JA, (1999) Lepidium latifolium L. ecology and control. USDA,
Agricultural Research Service. National Symposium on Tall
Whitetop-1999, Alamosa, Colorado. pp. 43-45.
Questions?