NORTH DAKOTA

SOUTH DAKOTA

MONTANA

MINNESOTA

Theodore 

Roosevelt

National Park

Arrowwood

National Wildlife

Refuge

Tewaukon National 

Wildlife Refuge

Ecological Effects

Because leafy spurge excludes other prairie plants 

(Belcher and Wilson, 1989), we were interested in 

understanding the mechanisms that allowed its dominance. We examined both above-ground (pollination) 

and below-ground (plant-soil feedback) processes. 

Pollination

Although invasive plants commonly compete with 

native plants for light and nutrients, they also may 

compete for pollinator services by attracting pollinators away from native flowers. On the other hand, a 

dense stand of flowering invasive plants may attract 

more pollinators to the area and, in the process, enhance 

pollination of neighboring natives. If insects are carrying a mixed pollen load when they visit native flowers, 

however, they may deposit pollen of other species, 

rather than the pollen necessary for native flower 

reproduction.

Leafy spurge provides large amounts of nectar and 

pollen in easily accessed flowers (cyathia) over a 4- to 

6-week period in the spring, and sometimes for a shorter 

period in the fall at TRNP (Larson and others 2006). 

Its abundance is much greater than that of the native 

flowering plants in the vicinity of an infestation, which 

led us to ask if spurge had an effect on pollination of 

native plants. Specifically, we wondered (1) does visitation to native flowers by pollinator insects vary between 

infested and noninfested sites, (2) does the amount of 

U.S. Department of the Interior

U.S. Geological Survey

Fact Sheet 2009–3066

August 2009

The Saga of Leafy Spurge (Euphorbia esula) in the 

Northern Great Plains

Printed on recycled paper

Leafy spurge (Euphorbia esula L.) is an invasive Eurasian perennial introduced into the United States as a contaminant of crop seed in 

the 1880s and 1890s. It typically forms monocultures in 

rangeland and natural areas of the northern Great Plains 

where, because of the latex that occurs in all parts of the plant, it is not 

consumed by naturally occurring herbivores. U.S. Geological Survey (USGS) 

scientists and their collaborators have been studying leafy spurge at Theodore 

Roosevelt National Park (TRNP) and at Arrowwood and Tewaukon National Wildlife Refuges in North Dakota since 

1998. Study findings have been published in Larson and Grace (2004), Larson and others (2006), Larson and others 

(2007), Jordan and others (2008), and Larson and others (2008). This fact sheet summarizes that body of research.

conspecific pollen (pollen from the same species as 

the recipient) on stigmas vary between infested and 

noninfested sites, and (3) does infestation influence 

the number of pollen species and proportion of heterospecific pollen (pollen from different species than the 

recipient) on native plant stigmas?

We found that although infestation by leafy spurge 

had an effect on pollinator visitation, the effect was 

neither consistent among species nor between years 

(Larson and others 2006; fig. 1). Nonetheless, there 

were fewer conspecific pollen grains on stigmas of 

native species within spurge infestations, and this did 

not vary between the 2 years of our study. We did not 

find a greater number of pollen species on native stigmas 

within infestations, likely because species diversity 

was depressed in these areas (Larson and others, 2006). 

Further studies of how the observed conspecific pollen 

deficit influences seed set for native plant populations 

are needed before firm conclusions can be drawn about 

how pollinator-mediated effects of leafy spurge influence native plant populations. 

Plant-Soil Feedback

Accumulating evidence suggests that substantial 

interactions between invasive plants and soil biota may 

influence the outcome of invasion events. A common 

way of investigating these interactions is through plantsoil feedback experiments: sterilized and live soils are 

conditioned by repeatedly growing either invasive or 

native species in them over several growth cycles. The 
Figure 1. Visits by pollinator taxa to native plant species and leafy spurge over 2 years. Native plant species are Campanula rotundifolia, 

Linum lewisii, and Oxytropis lambertii. NATURAL LOG [(VISITS PER 20 MINUTES) + 1]

0

0.5

1.0

1.5

2.0

2.5

Campanula rotundifolia

(bluebell)

Linum lewisii

(Lewis blue fax)

Oxytropis lambertii

(purple locoweed)

Euphorbia 

esula

(leafy spurge)

Bees 

EXPLANATION

Bumblebees

Flies

Butterflies

Wasps 

Infestation: No = not infested 

by leafy spurge; Yes = infested 

by leafy spurge. 

YEAR 2000 2001 2000 2001

Infestation

2000 2001 2000 2001

No Yes No Yes No Yes No Yes No Yes No Yes Yes Yes

performance of native species in the variously conditioned soils is measured. When we performed such an 

experiment with leafy spurge and a suite of native species 

common to the mixed-grass prairies of North Dakota 

(Jordan and others, 2008), we found that soils conditioned 

by leafy spurge had a negative effect on the growth of 

several native forb species, and further that this effect was 

mediated by soil biota living in unsterilized soil (fig. 2). 

This effect could help explain how leafy spurge becomes 

dominant, and may also help us develop strategic restoration plans that use species tolerant of changes in soil biota 

remaining even after an infestation has been controlled.

Biological Control

The biological control program for leafy spurge in 

the northern Great Plains is largely considered successful 

by land managers in the region (Hodur and others, 2006). 

Research by USGS scientists has demonstrated that the 

black flea beetles, Aphthona lacertosa/czwalinae (the 

two species cannot be distinguished in the field), have 

been effective in reducing populations of leafy spurge at 

TRNP (Larson and Grace, 2004) and at Arrowwood and 

Tewaukon National Wildlife Refuges (Larson and others, 

2008). Integrated pest management, in which more than 

one management tool is applied in combination, also has 

been used in efforts to control leafy spurge. Our research 

indicates that if a successful biological control program 

has been established, addition of herbicides may produce 

quicker reductions in spurge populations but may also 

disrupt the interactions between flea beetles and leafy 

spurge, reducing the effectiveness of the biological control 

organisms (Larson and others, 2007). Herbicide effects 

were short lived; spurge populations 2 to 3 years after 

herbicide treatment were indistinguishable from those that 

had only biological control. Our results therefore suggest 

that managers consider the need for rapid control versus 

the potential disruption of a biological control program 

before deciding to use herbicides in situations where 

biological control is effective.
Euphorbia esula (leafy spurge)

GRAMS PER INDIVIDUAL (LEAST SQUARE MEANS) 0.000

0.002

0.004

0.006

0.008

0.010

0.012

0.014

0.016

0.018

Agropyron cristatum (invasive grass)

0.000

0.005

0.010

0.015

0.020

0.025

Bromus inermis (invasive grass)

0.00

0.01

0.02

0.03

0.04

0.05

Bouteloua gracilis (native grass)

0.000

0.002

0.004

0.006

0.008

0.010

0.012

Koeleria pyramidata (native grass)

0.000

0.001

0.002

0.003

0.004

0.005

Stipa viridula (native grass)

0.000

0.002

0.004

0.006

0.008

0.010

0.012

0.014

0.016

Aster ericoides (native forb)

0.000

0.002

0.004

0.006

0.008

0.010

0.012

0.014

0.016

Linum lewisii (native forb)

0.000

0.002

0.004

0.006

0.008

Ratibida columnifera (native forb)

TREATMENT

IU NU IS NS

0.000

0.001

0.002

0.003

0.004

0.005

0.006

TREATMENT

IU NU IS NS

TREATMENT

IU NU IS NS

IU − invasive conditioning with unsterilized soil 

EXPLANATION

NU − native conditioning with unsterilized soil

IS − invasive conditioning with sterilized soil

NS − native conditioning with sterilized soil

Figure 2. Seedling biomass (mass of individual seedlings in a given 

area) of invasive and native species in response to soil conditioning and 

soil sterilization treatments. Soils were collected at Theodore Roosevelt 

National Park and conditioned by E. esula (leafy spurge) or native species 

(modified from Jordan and others, 2008).

Restoration of Previously Infested MixedGrass Prairie

Native prairie species do not always return after 

leafy spurge declines. To investigate why this occurs and 

to try to overcome the problem, we have identified three 

types of sites in the south unit of TRNP: sites that were 

never infested by leafy spurge, sites that were previously 

infested but are now dominated by native species, and 

sites that were previously infested but are now dominated 

by exotic species. Ordination (fig. 3) clearly illustrates 

that plots previously infested by leafy spurge but now 

dominated by native species are very similar to those plots 

that were never infested. In contrast, plots that were previously infested by leafy spurge but are now dominated by 

other exotic species show little overlap with never infested 

plots. The presence of native species in the seedbank has 

ruled out propagule availability as the reason for lack of 

native recruitment (D. Haines, unpublished data, 2009), so 

the question becomes, what allows native recruitment in 

some areas but not in others? 

Our current work addresses this question in several 

ways: (1) we have done experimental plantings in the 

previously infested sites to see if differences in performance of native species we observed in the greenhouse are evident in the field; (2) collaborators in the 
Figure 3. Ordination (by nonmetric multidimensional scaling 

analysis) of plots with respect to plant species cover at Theodore 

Roosevelt National Park. Axis 2 accounts for 37 percent and axis 3 

accounts for 28 percent of the variation in the data. Vegetation on the 

plots was the result of natural processes; no restoration was done.

AXIS 2

AXIS 3

 Never infested

 Previously infested,

 now exotic

Vegetation 

EXPLANATION

 Previously infested,

 now native

Agricultural Research Service (U.S. Department of 

Agriculture) are assessing pathogen loads on roots of 

our planted species; (3) collaborators at the University 

of Minnesota are assessing arbuscular mycorrhizal fungi 

communities associated with the planted species and 

leafy spurge; and (4) a graduate student at the University of Minnesota is examining effects of spurge root 

exudates (compounds released from roots into the soil) 

on native prairie species germination and growth. Our 

goal is to provide land managers with information that 

will assist them in developing successful restoration 

strategies for these degraded sites.

Partners and Collaborators

♦ Paulette Scherr, U.S. Fish and Wildlife Service, 

Arrowwood National Wildlife Refuge

♦ Kristine Askerooth, U.S. Fish and Wildlife Service, 

Tewaukon National Wildlife Refuge

♦ Nick Jordan, Sheri Huerd, Jennifer Larson, and Dustin 

Haines, University of Minnesota

♦ Tony Caesar and TheCan Caesar, U.S. Department of 

Agriculture, Agricultural Research Service

♦ Paula Andersen and Laurie Richardson, National Park 

Service, Theodore Roosevelt National Park

♦ Ron Royer and Margaret Royer, Minot State University

References Cited

Belcher, J.W., and Wilson, S.D., 1989, Leafy spurge and the 

species composition of a mixed-grass prairie: Journal of 

Range Management, v. 42, no. 2, p. 172–175.

Hodur, N.M., Leistritz, F.L., and Bangsund, D.A., 2006, 

Biological control of leafy spurge—utilization and implementation: Rangeland Ecology & Management, v. 59, issue 

5, p. 445–452.

Jordan, N.R., Larson, D.L., and Huerd, S.C., 2008, Soil modification by invasive plants—effects on native and invasive 

species of mixed-grass prairies: Biological Invasions, v. 10, 

no. 2, p. 177–190.

Larson, D.L., and Grace, J.B., 2004, Temporal dynamics of 

leafy spurge (Euphorbia esula) and two species of flea 

beetles (Aphthona spp.) used as biological control agents: 

Biological Control, v. 29, issue 2, p. 207–214.

Larson, D.L., Grace, J.B., and Larson, J.L, 2008, Long-term 

dynamics of leafy spurge (Euphorbia esula) and its biocontrol 

agent, flea beetles in the genus Aphthona: Biological Control, v. 

47, issue 2, p. 250–256, doi:10.1016/j.biocontrol.2008.07.016.

Larson, D.L., Grace, J.B., Rabie, P.A., and Andersen, P., 2007, 

Short-term disruption of a leafy spurge (Euphorbia esula) 

biocontrol program following herbicide application: Biological 

Control, v. 40, issue 1, p. 1–8.

Larson, D.L., Royer, R.A., and Royer, M.R., 2006, Insect visitation and pollen deposition in an invaded prairie plant community: Biological Conservation, v. 130, issue 1, p. 148–159.

By Diane L. Larson

For more information, contact:

Director

U.S. Geological Survey

Northern Prairie Wildlife Research Center

8711 37th Street SE, Jamestown, ND 58401

Telephone: 701–253–5500

World Wide Web: http://www.npwrc.usgs.gov