M. Sc. thesis, Ohio State University
ECOLOGY, DISTRIBUTION, AND CONTROL OF PURPLE LOOSESTRIFE (Lythrum salicaria) IN NORTHWEST OHIO
Gregory R. Balogh
1986
ABSTRACT
Purple loosestrife (Lythrum salicaria L.) is an exotic perennial wetland herb that is presently expanding its range within the marshes of northern United States and southern Canada. Purple loosestrife is of minimal value to wildlife, and its presence within a wetland severely limits marsh management options. Feasible purple loosestrife control methods are lacking, and information that allows documentation of local loosestrife distribution can be expensive to obtain. Pre-existing aerial photography was used to detect purple loosestrife stands. In addition, I investigated several techniques for possible purple loosestrife control; the effectiveness of the pre-emergent herbicide, Casoron, in killing purple loosestrife was evaluated, the effects of twelve different dosages of glyphosate in the form of Rodeo applied to purple loosestrife at 5 different portions of the growing season were evaluated, the depth and duration of flooding necessary to kill purple loosestrife seedlings was determined, and the relative competitive success of purple loosestrife planted with Polygonum lapathifolium (nodding smartweed), Echinochloa walteri (Walter's millet), and Cyperus fergenescens (chufa) was documented.
The remote sensing effort resulted in the documentation of 213 wetland sites containing purple loosestrife that comprised 1,287 ha (3,179 acres) of remnant Lake Erie marshes within Erie, Lucas, Ottawa, and Sandusky counties, Ohio. Aerial photographs acquired by the Agricultural Stabilization and Conservation Service allow for detailed annual monitoring of local loosestrife stands. Inspection of these aerial photographs exposed during different years will allow quantification of purple loosestrife's rate of spread within local marshes.
Casoron herbicide applied at 112-224 kg/ha (100-200 lbs./acre)
resulted in stem density changes ranging from +42% to -63%. Most
loosestrife roots within the treated area grew shoots the year
after the treatment. Typically, these treated plants were less
vigorous than untreated plants and were still 2-4 weeks behind
in flower and fruit development by mid-August. Casoron does not
control purple loosestrife as well as Rodeo, and Casoron treatments
cost 10 times more than similar Rodeo treatments. Casoron might
be useful in a spot treatment program in which it would be, for
some reason, easier to apply that Rodeo.
The glyphosate treatments ranged from 0.22 to 6.61 kg/ha (0.20
to 5.89 lbs./acre) active ingredient. Stem density changes as
a result of the 12 herbicide treatments approximated a typical
dose-response curve whereby increasingly smaller responses to
herbicide were observed with each incremental increase in herbicide.
Parameters that did not influence stem density changes on the
glyphosate treated plots include plant size, water depth at time
of treatment, and density of stems on the plot before treatment.
Parameters that significantly influenced herbicide response included herbicide solution concentration, volume of herbicide sprayed, and unknown marsh effects. Time of year of treatment might also have affect loosestrife's response to the herbicide, although whether response increased or declined with time was not consistent among marshes. Rodeo has potential to be a good chemical control agent for purple loosestrife, although my data indicate that at rates 6.5 kg/ha (5.79 lbs./ha), some plants within a marsh will survive a single treatment. Characteristics of a marsh or of plants within a marsh can significantly affect herbicide response. I was not able to identify the parameters that were affecting loosestrife's response to herbicide sprayed onto plants in my study plots, however.
Seedlings 5-15 cm tall that were submerged beneath 10 to 20 cm water for 3 weeks survived, and some of the treated plants went on to flower during the first year of growth. Satisfactory control of purple loosestrife seedlings was obtained after 7 weeks of flooding at depths of 30-100 cm in a pond in northwest Ohio during 1985. Depth and duration of flooding both significantly affected seedling mortality, and duration of flooding had a much more pronounced effect on the seedling mortality than did the water depth.
Experimental flooding of purple loosestrife seedlings was conducted again in 1986 in a pond near London, Ohio. Complete control of plants flooded with 30-90 cm water was achieved after only 5 weeks of flooding. Flooding is and effective purple loosestrife seedling control technique. Duration of flooding is more important than depth of flooding.
P. lapathifolium out-competed purple loosestrife during the first year of growth under northwest Ohio field conditions. E. walteri, and C. ferugenescens did not succeed in forming stands dense enough to shade out purple loosestrife seedlings. On all sub-plots, biomass of P. lapathifolium at the end of the growing season was greater than that of the other 3 planted species combined. P. lapathifolium was unsuccessful in out-competing purple loosestrife under the wet, reduced light conditions, present in an environmental control chamber. Although Polygonum lapathifolium can out-compete purple loosestrife during the first year of growth, the seeding rates used in this experiment were too large to allow consideration of cultivated seedling competition as a practical purple loosestrife control technique.
IIBC Final Report, February 1991
STUDY AND SCREENING OF POTENTIAL BIOLOGICAL CONTROL AGENTS OF PURPLE LOOSESTRIFE (Lythrum salicaria L.)
B. Blossey and D. Schroeder
A Report by the International Institute of Biological Control
February 1991
ABSTRACT
Purple loosestrife is a herbaceous perennial of European origin that has become a serious weed in marshes and alluvial wetlands, especially in the northeastern and north-central United States. There are no satisfactory means of control with the result that L. salicaria is forming dense monospecific stands after having replaced a diversified native flora. The biological control of the weed is expected to resolve the problem to a large extent.
The European root-mining weevil Hylobius transversovittatus and the two leaf-eating beetles, Galerucella calmariensis and G. pusilla, have a wide geographic range, live monospecific on L. salicaria, and are restricted to habitat conditions characteristic for the areas of North America infested by L. salicaria. It is expected that all three species can be established throughout the purple loosestrife distribution in North America and will have no detrimental impact on native or ornamental plant species. The combined effect of the three beetle species should greatly reduce the vigor and competitive power of purple loosestrife and prevent it from dominating the native flora.
A report to the National Park Service
August 16, 1992
CONTROL OF PURPLE LOOSESTRIFE (Lythrum salicaria L.) AT INDIANA DUNES NATIONAL LAKESHORE BY CUTTING FOLLOWED BY OVERWINTER FLOODING
L. Comas, K. Edwards, and B. Lynch
Department of Botany
University of Wisconsin-Madison
Madison, WI 53706
ABSTRACT
Purple loosestrife (Lythrum salicaria L.) is an aggressive invader of North American wetland that has been resistant to previous control methods. The lack of success with control methods may be the result of an inadequate application period in the case of herbicide use, or application of control methods at a sub-optimal time in the case of previous cutting methods. While cutting loosestrife stems was tried in the past, it was always tried during the summer. Beule (1979) showed that cattails could be controlled by cutting stems at the end of the growing season, followed by flooding over the winter. The results of this experiment show that purple loosestrife stems and biomass were significantly decreased by similar procedures.
Biological Control Laboratory Newsletter
University of Guelph
THE IMPACT OF Galerucella calmariensis L. (COLEOPTERA: CHRYSOLMELIDAE) ON PURPLE LOOSESTRIFE (Lythrum salicaria L.) UNDER CAGED FIELD CONDITIONS
A.M.Cooper, J. E. Laing, and J.E. Corrigan
Department of Environmental Biology
University of Guelph
Guelph, Ontario, Canada
N1G 2W1
NO ABSTRACT
Wetlands (1996) 16(1): 95-98
WETLAND PLANT RESPONSES TO VARYING DEGREES OF PURPLE LOOSESTRIFE REMOVAL IN SOUTHEASTERN ONTARIO, CANADA
T. Shane Gabor*, Tip Haagsma**, and Henry R. Murkin*
*Institute for Wetland and Waterfowl Research
c/o Ducks Unlimited Canada
P.O. Box 1160
Stonewall, MB Canada
R0C 2Z0
s_gabor@ducks.ca
h_murkin@ducks.ca
**DowElanco Canada Inc.
375 Exmouth St.
Sarnia, ON Canada
N7T 5N8
ABSTRACT
This study examined the response of native vegetation to varying levels of purple loosestrife (Lythrum salicaria) removal and determined its impact on subsequent loosestrife germination and establishment in a southern Ontario wetland during 1993 and 1994. The study site was treated in 1991 with varying dosages of triclopyr amine herbicide, the triethylamine salt formulation of triclopyr [[(3,4,6-trichloro-2-pyridinyl)oxy]acetic acid]; 4.0, 8.0, and 12.0 kg active ingredient (a.i.)/ha. Different levels of adult loosestrife control were achieved. The lowest density of adult loosestrife was observed in the 8.0 and 12.0 kg a.i./ha treatment plots where root kill was the most effective. Most new adult loosestrife plants in the 8.0 and 12.0 kg a.i./ha treatment plots were established from seed. The highest densities of loosestrife seedlings and grass (Gramineae) species were observed in the treatment plots with the lowest number of adult loosestrife plants (12.0 kg a.i./ha). Sedge species (Carex spp.) did not differ between treatment levels during 1993 and 1994. Loosestrife seedling densities decreased from 1993 to 1994, suggesting that increased native plant species can slow the rate of loosestrife reestablishment from the seed bank. Native vegetation seems to replace adult loosestrife for a limited time following herbicide application; however, without subsequent treatment, loosestrife will slowly reinvade a wetland.
Journal of Aquatic Plant Management (1995) 33: 48-51.
Effects of Triclopyr Amine on Purple Loosestrife and Non-target Wetland Plants in
South-eastern Ontario, Canada
T. SHANE GABOR, T. HAAGSMA, H.R. MURKIN, AND E. ARMSON
Institute for Waterfowl and Wetland Research
c/o Ducks Unlimited Canada
Box 1160
Stonewall, Manitoba Canada
R0C 2Z0
s_gabor@ducks.ca
h_murkin@ducks.ca
ABSTRACT
We studied the effects of triclopyr amine, the triethylamine salt formulation of triclopyr [[(3,4,6-trichloro-2-pyridinyl)oxy] acetic acid] on purple loosestrife (Lythrum salicaria L.) and non-target vegetation in a southern Ontario wetland during 1991 and 1992. Triclopyr was applied during bud to early bloom stage at rates of 4.0, 8.0, and 12.0 kg/ha. During 1991, all treatment levels effectively controlled the aboveground portion of purple loosestrife. Grasses (family Gramineae) were unaffected during 1991, however, sedge species (Carex spp.) declined in numbers at higher treatment levels. At 1 year, post-treatment, adult purple loosestrife were not present in the 12.0 kg/ha treatment indicating that triclopyr effectively killed the root system. Seedlings dominated the total number of loosestrife plants in the 8.0 and 12.0 kg/ha treatment plots 1 year post-treatment. Sedges recovered in 1992 and grasses increased above 1991 levels. Removal of adult purple loosestrife allowed more light to reach the substrate surface and created favorable conditions for seed germination and plant growth. Triclopyr amine can effectively reduce adult loosestrife stem densities, however, additional herbicide applications may be required to prevent re-establishment through regeneration from the seed bank.
Journal of Aquatic Plant Management (1990) 28: 98-100.
Effects of Clipping Purple Loosestrife Seedlings During a Simulated Wetland Drawdown
T. Shane Gabor and H.R. Murkin
Institute for Waterfowl and Wetland Research
c/o Ducks Unlimited Canada
Box 1160
Stonewall, Manitoba Canada
R0C 2Z0
s_gabor@ducks.ca
h_murkin@ducks.ca
Introduction
Purple loosestrife (Lythrum salicaria L.) was inadvertently introduced to the northeast coast of North America from Europe in the early 1800s and has subsequently spread across mid-latitude wetlands (Thompson et al. 1987). It is an erect herbaceous perennial producing many small viable seeds that are readily dispersed by wind, water, and animals (Shamsi and Whitehead 1977; Thompson et al. 1987). This species spreads rapidly and forms dense monospecific stands (Shamsi and Whitehead 1974) that outcompete and eliminate important native wetland wildlife food plants (Malecki and Rawinski 1985; Smith 1964). Loss of native habitat to loosestrife is a major concern of wetland and waterfowl managers.
Wetlands (1993) 13(3): 224-227
Effects of Shallow Flooding on Newly Established Purple Loosestrife Seedlings
Margaret J. Haworth-Brockman and Henry R. Murkin
Institute for Wetland and Waterfowl Research
c/o Ducks Unlimited Canada
P.O. Box 1160
Stonewall, Manitoba
R0C 2Z0
h_murkin@ducks.ca
Robert T. Clay
Ducks Unlimited Canada
566 Welham Rd.
Barrie Ontario
L4M 6E7, Canada
ABSTRACT
Purple loosestrife (Lythrum salicaria) is a nuisance exotic species that displaces native plants and has little value as food or habitat for wildlife. Attempts to control adult plants have had limited success. We investigated the effects of shallow flooding (<30cm) on the growth and survival of purple loosestrife seedlings. pots containing purple loosestrife seedlings were assigned to each of 12 treatment combinations: 3 seedling height categories and 4 flooding depths. Mean stem densities were not affected by the treatments (P>0.05). The flooding treatments significantly affected mean stem heights, but there were no identifiable trends within size classifications. All seedlings continued to grow during the experiment. The survival of any purple loosestrife plants can have serious implications in wetlands. The results from this study indicate that shallow flooding is not an effective approach to limiting or preventing establishment of purple loosestrife seedlings.
Weed Science (1996) 44: 143-147
INFLUENCE OF NONTARGET NEIGHBORS AND SPRAY VOLUME ON RETENTION AND EFFICACY OF TRICLOPYR IN PURPLE LOOSESTRIFE (Lythrum salicaria)
Elizabeth J. Stamm Katovich, Roger L. Becker, and Brad D. Kincaid
Department of Agronomy and Plant Genetics
University of Minnesota
St. Paul, MN 55108
ABSTRACT
Greenhouse studies were conducted to determine the influence of plant density and spray volume on the retention spray depostion, efficacy, and translocation of the amine salt of triclopyr in purple loosestrife. More spray solution was retained on leaves at 935 L ha-1 than at 94 L ha-1 at population of 0, 4, or 8 nontarget neighbors. Spray coverage decrease with the decreasing height within the plant canopy when spray cards were placed in the top, middle, and soil surfaace adjacent to the central target plant. Within a population, spray card coverage generally increased as spray volume increased. Regrowth from the crown was affected by spray volume, and uniform spray coverage of the plant was required for adequate control of vegetative regrowth and was achieved with spray volumes of 374 and 934 L ha-1 spray volume. Regrowth of purple loosestrife was greater at 94 L ha-1 at all three plant populations indicating that less herbicide penetrated the canopy to reach the basal portion of the plant. A laboratory experiment was conducted to investigate the translocation of radiolabelled triclopyr to roots and crowns of purple loosestrife. Only 0.3 to 1.4% of absorbed 14C-labelled material was translocated to roots and crowns. Low spray volumes and dense stands of purple loosestrife would likely result in poor control because inadequate amounts of triclopyr reach the basal portion of the plant and translocate to vegetative propagules.
Nomenclature: Triclopyr; [(3, 5, 6-trichloro-2-pyridinyl)oxy]acetic acid
Purple loosestrife (Lythrum salicaria L. # LYSTA)
An Ontario Federation of Anglers and Hunters Publication 1992
A UNIVERSAL MANUAL FOR PURPLE LOOSESTRIFE CONTROL
Cathy Keddy
Consulting Ecologist
Ontario Federation of Anglers and Hunters
P.O. Box 2800
Peterborough, Ontario K9J 8L5
INTRODUCTION
Purple loosestrife (Lythrum salicaria L.) is a tall plant with a striking spike of bright fuscia flowers (see back inside cover), found in wetland habitats across North America. It is of Eurasian origin and was introduced to this continent in the early 1800's (Stuckey 1980). Since that time it has spread rapidly to become a serious threat to native vegetation and wildlife (Thompson et al. 1987).
The impact of purple loosestrife on native vegetation has been disastrous. It readily out-competes native plant species (Gaudet and Keddy 1988) forming dense, self-perpetuating monocultures. Wildlife, which in turn relies on native wetland vegetation for food, nesting and shelter, is threatened because purple loosestrife meadows do not provide suitable habitat (Thompson et al. 1987; Rawinski and Malecki 1984; Kiviat 1978; Purple Loosestrife Task Force n.d.). In the United States alone, 190,000 hectares of wetland habitat are lost annually to purple loosestrife (Thompson et al. 1987). The loss of these wetlands in terms of purchase price and land use can be estimated, but the cost of losing irreplaceable, provincially or nationally significant wetlands and wildlife cannot.
Red-winged blackbirds appear to be the only documented wildlife species that actually benefit from this plant, finding preferential nesting habitat within the stalks (Rawinski and Malecki 1984).
Despite our early knowledge of the problem purple loosestrife poses to native wetland flora and fauna (Fernald 1940, Louis-Marie 1944), it is only recently that its invasion of Ontario has become a high profile concern. The majority of southern Ontario wetlands have low to intermediate densities of purple loosestrife while the density is high in the Grand River, Rideau River, and Ottawa River valleys.
This report provides wetland managers throughout North America with a practical, systematic approach for dealing with the problem. It is the tool managers require to determine priorities for purple loosestrife management, management options, and the success of the management practices implemented. This protocol addresses four points in the seven-point, province-wide management strategy previously proposed (Keddy 1988) for the Province of Ontario, and it can be applied to any wetland on the continent.
Natural Heritage League report, September 1988
A REVIEW OF Lythrum salicaria (PURPLE LOOSESTRIFE) ECOLOGY AND MANAGEMENT: THE URGENCY FOR MANAGEMENT IN ONTARIO
Cathy Keddy
644 Chapel St.
Ottawa, Ontario
K1N 7Z9
SUMMARY
Lythrum salicaria (purple loosestrife) is a tall plant with a striking spike of bright purple flowers, found in the wetland habitats of Ontario. It is a European species that was introduced to North America in the early 1800's and since has spread rapidly across the continent, becoming a serious threat to native vegetation and wildlife.
The impact of Lythrum salicaria on native vegetation has been disastrous. It readily out-competes native plant species forming dense, self-perpetuating monocultures. Wildlife which in turn relies on native wetland vegetation for food, nesting, and shelter is threatened because Lythrum salicaria meadows do not provide suitable habitat. In the United States alone, 190,000 hectares of wetland habitat are lost annually to Lythrum salicaria. The loss of these wetlands in terms of purchase price and land use can be estimated, but the cost of losing irreplaceable, provincially or nationally significant wetlands cannot.
Lythrum salicaria is easily recognized in mid to late summer when it is in bloom. The flowers are insect pollinated. Seeds are dispersed mainly by moving water, but may also adhere to wildlife or be transported by off-road vehicles or motor boats. Soil moisture is the most important factor for seed germination. Seeds germinate best on moist, open ground and plants will survive in 50% full sunlight. Although reproduction from seed is important in population establishment, new plants may also grow from stem or root fragments.
Lythrum salicaria spreads rapidly and out-competes native species because it produces seed prolifically, and has numerous short and long range dispersal mechanisms, can tolerate a wide variety of physical and chemical environments and can adapt to changing environmental conditions. The spread of Lythrum salicaria within a watershed tends to be insidious. Initially a few plants may establish and prolifically produce seed. Then, under the right disturbance conditions mass seed germination occurs and the population explodes. Management of Lythrum salicaria hinges on detecting the establishment of plants early, before dense populations can form.
Considerable attention had been paid to developing methods for the control of Lythrum salicaria and many research projects are currently underway to improve methods. In the past, technique development has concentrated on management in artificially controlled wetlands where wildlife productivity is the main goal. More recently, the focus is on Lythrum salicaria management and the maintenance of native plant communities in natural wetlands.
Lythrum salicaria management involves preventing the establishment of new populations (control) and preventing the spread of dense, established monocultures (containment). Methods for eradicating dense monocultures of Lythrum salicaria that do not further enhance proliferation are not currently available. Biological control, when developed may be appropriate for natural wetlands include hand-pulling, the use of herbicides, and cutting. The first two are the most effective. Techniques applicable for managing Lythrum salicaria within a particular wetland depend on the density of Lythrum salicaria, associated species, occurrence of standing water, accessibility, herbicide regulations, and cost and manpower.
Lythrum salicaria is found in most of Ontario's significant wetlands. In some areas, dense populations of Lythrum salicaria have already eliminated native wetland vegetation. In other areas, Lythrum salicaria is just beginning to invade. Despite the demonstrated environmental impact of Lythrum salicaria on native vegetation and wildlife in wetlands, there is currently no organized program to control Lythrum salicaria in Ontario.
A six part control program for Lythrum salicaria management in Ontario is outlined in this report consisting of the following steps:
If we are to retain excellent examples of some of the most provincially and nationally significant wetland habitats in Ontario, the recommendations outlines in this report for Lythrum salicaria must be acted on now. For wetlands known to have significant native plant communities (e.g., Westmeath, Presqu'ile provincial parks), Lythrum salicaria should be a management priority.
Biological Control Laboratory Newsletter
University of Guelph
FIELD IDENTIFICATION OF GALERUCELLA BEETLES: BIOLOGICAL CONTROL AGENTS OF PURPLE LOOSESTRIFE
J. E. Laing and J. E. Corrigan
Department of Environmental Biology
University of Guelph
Guelph, Ontario, Canada N1G 2W1
NO ABSTRACT
New York Fish and Game Journal (1985) 32(1) : 9-19
NEW METHODS FOR CONTROLLING PURPLE LOOSESTRIFE
Richard A. Malecki
Assistant Leader
New York Cooperative Wildlife Research Unit
Cornell University; Ithaca, New York 14753
Thomas J. Rawinski
Research Assistant
New York Cooperative Wildlife Research Unit
Cornell University; Ithaca, New York 14753
ABSTRACT
New methods for controlling purple loosestrife were investigated at the Howland Island Management Area in central New York during 1978-1980. Neither late summer cutting nor partial flooding had more than a seasonal impact on the plant, but cutting followed by flooding in the same year may result in significant stress. Complete inundation was successful in reducing the number of plants when continued for two or more growing seasons. The herbicide glyphosate was extremely effective (100 percent control) on test plots when applied at a rate of 1.7 kilograms per hectare in mid-August. Viability of seeds from treated plants was sufficient for concern. Sowing Japanese millet on exposed moist soil sites at a rate of 34 kilograms per hectare following a drawdown resulted in successful control of loosestrife in those areas as well as production of a desirable waterfowl food.
Wetlands Research Program Technical Report WRP-SM-4
June 1995
SELECTIVE CONTROL OF PURPLE LOOSESTRIFE WITH TRICLOPYR
Linda S. Nelson, Kurt D. Getsinger, and Jan E. Freeman
U.S. Army Corps of Engineers
Waterways Experiment Station
3909 Halls Ferry Road
Vicksburg, MS 39180-6199
ABSTRACT
Purple loosestrife (Lythrum salicaria) is an exotic wetland weed that rapidly displaces native vegetation resulting in monotypic stands that reduce vegetative diversity and degrade wildlife habitat. Use of nonchemical management techniques, e.g., flooding, draining, cutting, and burning, is inherently nonselective and seldom results in long-term control of purple loosestrife infestations. Some herbicides offer a selective technique for reducing purple loosestrife levels, eradicating pioneer colonies of the plant, and restoring native wetland communities.
The objectives of this study were to evaluate effectiveness of the herbicide triclopyr on purple loosestrife, and to monitor changes in the plant community following triclopyr treatment. Stands of purple loosestrife, located in the Upper Mississippi National Wildlife and Fish Refuge, MN, were treated with an amine formulation of triclopyr (Garlon 3A) on 30 June 1992. Application rates were 0.75 and 1.0 percent Garlon 3A. Percent cover of purple loosestrife and associated plant species were monitored using line-intercept techniques pretreatment, and at 10 weeks and 2 years posttreatment. Results showed that Garlon 3A is an effective product for significantly reducing purple loosestrife cover; however, seedling recruitment can be expected. Although data showed no significant differences between the rates tested, areas tested with the higher rate had less regrowth. This research resulted in a chemical technique for controlling purple loosestrife in wetland communities that includes minimizing damage to nontarget plants, particularly monocots, while offering a potential for restoring a diverse plant community.
M.Sc. Thesis, Cornell University
THE ECOLOGY AND MANAGEMENT OF PURPLE LOOSESTRIFE (Lythrum salicaria L.) IN CENTRAL NEW YORK
Thomas J. Rawinski
January 1982
ABSTRACT
Purple loosestrife (Lythrum salicaria L.) is an introduced perennial herb which has had a detrimental impact on indigenous North American wetland vegetation and associated wildlife habitats. Particularly severe infestations have occurred at a number of wildlife management areas, where the plant is considered a weed. This research was undertaken to help solve the purple loosestrife weed problem by gathering basic life history and ecological information about the plant and developing strategies for its control.
Field experiments were conducted from 1978-1980, primarily at Montezuma National Wildlife Refuge and Howland Island Wildlife Management Area in central New York. The response of purple loosestrife to a wide variety of treatments was studied by monitoring marked individuals or populations. Wildlife use of the plant was investigated through the use of exclosures and a line transect survey.
Life history experiment revealed that seed viability decreased from 99% to 80% following a two year storage period in a natural body of water. Seedling densities as high as 20 000/m2 were observed, and the rate of seedling mortality was directly related to the rate of shoot growth. Virtually all seedlings surviving to the end of the growing season resumed growth the following spring. Phenology of bloom varied slightly between years, and periods of early, peak, and late bloom were identified.
At a drawn down marsh where purple loosestrife grew with cattail (Typha glauca Godr.), loosestrife density increases during 1978-80, while cattail density decreased. However, cattail suppressed the growth of loosestrife in marshes where standing water was present throughout most of the growing season.
Wildlife use of adjacent purple loosestrife and cattail stands differed. Muskrats (Ondatra zibethicus) and long-billed marsh wrens (Cistothorus palustris) used the cattail cover almost exclusively, whereas most red-winged blackbird (Aeglaius phoeniceus) nest were found in loosestrife. The loss of open water space to purple loosestrife is probably a serious, but as yet undocumented impact of the plant on wetland wildlife.
The effectiveness of purple loosestrife control methods vary widely. Cutting all loosestrife shoots in late August resulted in 54% shoot reduction in the following year, while only a 34% reduction was achieved by cutting in early August. Cut shoots left on moist soil developed adventitious roots and continued growth. Raised water levels reduced purple loosestrife density in marshes where carp (Cyprinus carpio) were abundant, but at a marsh containing no carp, loosestrife was only slightly stressed following two years of flooding. Aerenchyma and adventitious roots were evident four days after plants were partially submerged. Late summer cutting of loosestrife followed by burning results in control that was slightly less effective than cutting alone.
Glyphosate herbicide, when applied to loosestrife during the period of peak bloom resulted in 99% control and led to the natural establishment of desirable indigenous vegetation. Seeded Japanese millet [Echinochlos frumentacea (Roxb.)Link] effectively out-competed both seeded and naturally established loosestrife seedlings. This fast growing wildlife food plant might be used to minimize loosestrife infestations during periods of marsh drawdown.
Generally, purple loosestrife becomes established and flourishes in disturbed wetland habitats. Recognition of this characteristic of the plant is the key to understanding and controlling its spread.
Report to the Metropolitan Council, December 1989
Department of Natural Resources Management, MN
INCIDENCE, SPREAD, AND CONTROL STUDIES OF PURPLE LOOSESTRIFE (Lythrum salicaria L.) IN HENNEPIN PARKS
Luke C. Skinner and Thomas O. Hollenhorst II
Suburban Hennepin Regional Park District
Department of Natural Resources Management
3800 County 24, Maple Plain, MN 55359
GENERAL INTRODUCTION
In the spring of 1987, Suburbs Hennepin Regional Park District (Hennepin Parks) received a $33,000 grant from the Metropolitan Council for a 3-year study of purple loosestrife (Lythrum salicaria L.). Purple loosestrife has been recorded in 11 of 19 Hennepin Parks' properties over the last 10 years. If left unchecked, purple loosestrife will likely replace native wetland vegetation throughout the Hennepin Parks' system. This study was designed to document the incidence and rate of spread of purple loosestrife in Hennepin Parks, evaluate new control methods for purple loosestrife, document the impact these methods have on the surrounding wetland vegetation, and finally, to recommend control methods which are safe and effective for use on wide-scale control efforts in future years.
Purple loosestrife is an emergent aquatic plant that grows very will in a variety of wetland habitats. This perennial herb is native to Eurasia but can now be found nearly worldwide (Shamsi and Whitehead 1974). Purple loosestrife was first reports to North America in 1814 (Pursh 1914). Since that time, the plant has invaded wetland throughout the United States and Canada, especially the glaciated wetlands of the northeast (Stuckey 1980). In many of these wetlands, it has become an aggressive weed which can out-compete and displace native wetland vegetation. Purple loosestrife can form large monotypic stands where a once-diverse wetland eco-system lived. This loss of plant diversity quickly leads to the loss of wildlife diversity (J. Bender 1986). Once purple loosestrife becomes established in a wetland, it can persist for decades.
New York Fish and Game Journal (1961) 11(1):35-46
EXPERIMENTAL CONTROL OF PURPLE LOOSESTRIFE (Lythrum salicaria)
Ralph H. Smith
Senior Wildlife Biologist
New York State Conservation Department
ABSTRACT
Trial plots of purple loosestrife were treated with various herbicides. Control, but not eradication, was best obtained by foliar applications of water solutions or oil and water emulsions of the so-called low-volatility esters of 2, 4, 5-T or 2, 4-D and 2, 4, 5-T in mixture, or silvex, at a concentration of 8 pounds acid equivalent per acre when at least 200 gallons of total solution were applied per acre. Satisfactory control did not result from treatment with various amine salts of 2, 4-D, the isooctyl ester of 2, 4-D, a formulation of 2, 3, 6-TBA, amitrole, or ammonium sulfamate.
Wildlife Society Bulletin (1993) 21: 56-64
REDUCTION OF PURPLE LOOSESTRIFE ESTABLISHMENT IN MINNESOTA WETLANDS
Charles H. Welling
Department of Agronomy and Plant Genetics
University of Minnesota, St. Paul, MN 55108
Roger L. Becker
Department of Agronomy and Plant Genetics
University of Minnesota, St. Paul, MN 55108
SUMMARY
Our objective was to determine whether establishment of purple loosestrife through recruitment from seed banks can be reduced by use of either 2,4-D herbicide or competitor plant species. These approaches were evaluated with soil collected from 2 Minnesota wetlands and maintained in outdoor flats where water levels were controlled. In flats, application of 2,4-D to seedling communities reduced loosestrife frequency and population density by 44 and 94% respectively. Application of 2,4-D also reduced dicot species richness. In flats, seeding of Italian ryegrass reduced loosestrife seedling density by 72% in 1 but not both years of the study; seeding Japanese millet did not reduce loosestrife seedling density. In wetlands where water levels were uncontrolled, 2,4-D applied to field quadrats reduced loosestrife seedling density by 78%. Application of 2,4-D also reduced both biomass of dicots other than loosestrife and dicot species richness in field quadrats. Competitors failed to establish in field quadrats and consequently had no effect on seedling establishment in study wetlands. Because it is difficult to reduce loosestrife establishment, managers should minimize seed bank development by attempting to eliminate recently established populations of scattered plants before they attempt to control long-established, mono-dominant stands. Application treatments to reduce loosestrife establishment also may alter establishment of other plants, the desirability of which will depend on management objectives.
Environmental Management (1989) 13(3): 365-370.
MIGRATION AND CONTROL OF PURPLE LOOSESTRIFE (Lythrum salicaria L.) ALONG HIGHWAY CORRIDORS
Douglas A. Wilcox
National Fisheries Research Center-Great Lakes
US Fish and Wildlife Service
1451 Green Road
Ann Arbor, Michigan 48105 USA
ABSTRACT
The east-west density gradient and the pattern and mode of migration of the wetland exotic, purple loosestrife (Lythrum salicaria L.) were assessed in a survey of populations along the New York State Thruway from Albany to Buffalo to determine if the highway corridor contributed to the spread of this species. During the peak flowering season of late July and early August, individual colonies of purple loosestrife were identified and categorized into three size classes in parallel belt transects consisting of the median strip and highway right-of-way on the north and south sides of the road. Data were also collected on the presence of colonies adjacent to the corridor and on highway drainage patterns. Although a distinct east-west density gradient existed in the corridor, it corresponded to the gradient on adjacent lands and was greatly influenced by a major infestation at Montezuma National Wildlife Refuge. The disturbed highway corridor served as a migration route for purple loosestrife, but topographic features dictated that this migration was a short-distance rather than a long-distance process. Ditch and culvert drainage patterns increased the ability of purple loosestrife to migrate to new wetland sites. Management strategies proposed to reduce the spread of this wetland threat include minimizing disturbance, pulling by hand, spraying with glyphosate, disking and mowing.
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