Mapping the Purple Menace: Spatiotemporal Distribution of Purple Loosestrife (Lythrum Salicaria) Along Roadsides in Northern New York State

Purple loosestrife (Lythrum salicaria L.) is an invasive herbaceous plant, frequently found in wetlands and along roadsides throughout northern New York State. Its propensity to create monoculture stands in wetlands has resulted in intensive management in parts of its range, including central New York and Ontario and Quebec. The goal of this study was identifying the extent of infestations and to determine factors that promote the spread of purple loosestrife in order to determine best land use practices to reduce the spread of this highly invasive wetland plant." We attempted to answer several questions: What is the level of infestation along roadsides? Does mowing contribute to the spread? How do culverts under roadways influence the spread? Between mid-July and mid-August in 2017–2019, we mapped all infestations along 150 km (93 miles) of state highway north of the Adirondack Park and south of the St. Lawrence River using the Environmental Systems Research Institute (ESRI) Collector app. We mapped the size and locations of infestations, in addition to collecting information on the plants within 1 m, recording over 100 additional species. The results of our preliminary analysis revealed significant increase in the number of plants over the study time (P < 0.001), including several hundred more infestations than had previously been recorded. We did not find any evidence that mowing promotes the spread of loosestrife. There were many more individual infestations in ditches along highways, but much larger and denser infestations in wetlands (P = 0.003 in 2019). We observed that culverts, drainage conduits under roadways, frequently had purple loosestrife on both sides of the road. We also found that culverts appear to serve as corridors that promote the spread of purple loosestrife from one side of the road to the other. We recommend working with the local landowners and NYS Department of Transportation to contain the spread and continue to propagate and spread the biological control.

Lythrum salicaria (purple loosestrife).

L. salicaria, an Old World native, is a highly invasive species of wetlands in North America, beginning to spread rapidly about 140 years after its accidental introduction around 1800. It is a very variable species with an ability to occupy numerous habitats and substrates with the exception of dry places. Its spread and persistence in ecosystems is supported by very high seed production, a vigorous and persistent root system and rapid growth. It is an invasive species and/or noxious weed in almost all states and provinces of Canada and the USA where it is a serious threat to many sensitive wetland ecosystems.

Throwing Out the Bathwater but Keeping the Baby: Lessons Learned from Purple Loosestrife and Reed Canarygrass

Historic ignorance of species’ native range, expansion due to unintentional involvement by vectors, and their quiet evolution has caused several invasive species to become “poster children,” such as purple loosestrife (Lythrum salicaria), reed canarygrass (Phalaris arundinacea), and others. Common misconceptions on how these became problematic have involved a variety of causes, including ignorance of species’ ability to intercross and create introgressive hybrids, lack of insects for control, wind pollination, and intercontinental distribution from their native range. Current research focuses on how misappropriating the historical contexts can reverse our misconceptions of native species being noninvasive and how this affects control by land managers. Purple loosestrife and reed canarygrass will be used as example species to demonstrate challenges that native vs. exotic, intra-, and interspecific differences confer to land managers. Issues such as a lack of phenotypic differences challenge land managers’ charge to control invasive individuals yet retain the noninvasives. This is fraught with challenges when native vs. exotic status is invoked or cultural values are entwined. To avoid a monumental impasse, particularly when native and exotic types are phenotypically indistinguishable, this dilemma could be solved via modern techniques using molecular biology.

Discrimination of leafy spurge (Euphorbia esula) and purple loosestrife (Lythrum salicaria) based on field spectral data

Leafy spurge (Euphorbia esula L.) and purple loosestrife (Lythrum salicaria L.) are invasive weeds that displace native vegetation. Herbicides are often applied to these weeds during flowering, so it would be ideal to identify them early in the season, possibly by the leaves. This paper evaluates the spectral separability of the inflorescences and leaves of these plants from surrounding vegetation. Leafy spurge, purple loosestrife, and surrounding vegetation were collected from sites in southeastern North Dakota and subjected to spectral analysis. Partial least-squares discriminant analysis (PLS-DA) was used to separate the spectral signatures of these weeds in the visible and near-infrared wavelengths. Using PLS-DA, the weeds were discriminated from their surroundings with R2 values of 0.86 to 0.92. Analysis of the data indicated that the bands contributing the most to each model were in the red and red-edge spectral regions. Identifying these weeds by the leaves allows them to be mapped earlier in the season, providing more time for herbicide application planning. The spectral signatures identified in this proof of concept study are the first step before using ultra–high resolution aerial imagery to classify and identify leafy spurge and purple loosestrife.

Bookkeeping of insect herbivory trends in herbarium specimens of purple loosestrife ( Lythrum salicaria )

The potential use of herbarium specimens to detect herbivory trends is enormous but largely untapped. The objective of this study was to reconstruct the long-term herbivory pressure on the Eurasian invasive plant, purple loosestrife ( Lythrum salicaria ), by evaluating leaf damage over 1323 specimens from southern Québec (Canada). The hypothesis tested is that that the prevalence of herbivory damage on purple loosestrife is low during the invasion phase and increases throughout the saturation phase. Historical trends suggest a gradual increase in hole feeding and margin feeding damage from 1883 to around 1940, followed by a period of relative stability. The percentage of specimens with window feeding damage did not begin to increase until the end of the twentieth century, from 3% (2–6%) in 1990 to 45% (14–81%) in 2015. Temporal changes in the frequency of window feeding damage support the hypothesis of an increasing herbivory pressure by recently introduced insects. This study shows that leaf damage made by insects introduced for the biocontrol of purple loosestrife, such as coleopterans of the Neogalerucella genus, can be assessed from voucher specimens. Herbaria are a rich source in information that can be used to answer questions related to plant-insect interactions in the context of biological invasions and biodiversity changes. This article is part of the theme issue ‘Biological collections for understanding biodiversity in the Anthropocene’.

Lythrum salicaria(Purple Loosestrife) Control with Herbicides: Multiyear Applications

This study evaluated the effectiveness of 14 herbicide treatments for purple loosestrife (Lythrum salicariaL.) control over a period of 10 yr. The study commenced in 2000/2001 at four wetland locations in Nebraska. The evaluated herbicides included: glyphosate at 2.2 and 3.4 kg ha−1; 2,4-D dimethylamine at 1.4 and 2.8 kg ae ha−1; triclopyr at 1.3 and 2.1 kg ae ha−1; imazapyr at 1.1 and 1.7 kg ae ha−1; metsulfuron at 0.042 and 0.084 ai kg ha−1; fosamine at 13.5 and 22.4 kg ai ha−1; triclopyr at 1.3 kg ae ha−1plus 2,4-D amine at 1.4 ae kg ha−1; and metsulfuron at 0.042 kg ai ha−1plus 2,4-D amine at 1.4 kg ae ha−1. Some treatments provided excellent control (90%) that lasted only one season, while others suppressedL. salicariagrowth for multiple seasons, depending on the location and the age ofL. salicariastand. Application of higher rates of glyphosate, imazapyr, and metsulfuron consistently provided excellent control (≥90%) ofL. salicariathat lasted 360 d after treatment at most locations. Application of fosamine and the lower rate of 2,4-D amine provided the leastL. salicariacontrol at most locations. The older theL. salicariastand, the more multiple applications of herbicides were needed to completely controlL. salicaria. Generally, there were higher percentages of grasses in the 2,4-D-, triclopyr-, and metsulfuron-treated plots compared with higher percentages of broadleaf species in the glyphosate- and imazapyr-treated plots at each location.

18. Controlling Purple Loosestrife Populations in the Kingston and Surrounding Areas

Purple loosestrife (Lythrum salicaria) is an invasive plant species that has affected agriculture and wildlife across Canada. The weed is not native to Canada; however in municipalities like Kingston and the surrounding area, it has caused tangible problems. We will strive to engage a government partner (City of Kingston), community organization (ON Invasive Species Awareness Program), and a local resident throughout the completion of our research and regarding the viability of solutions proposed. First, we will examine the origins of the plant in Canada, emphasizing the reproductive characteristics that make the purple loosestrife a powerfully invasive species. Next, we will analyze the impact of the purple loosestrife from three perspectives: (1) the impact on native plant communities; (2) the impact on native animal communities; (3) the impact on human life. We will then evaluate current bio management controls, as utilized by other governments, such as the introduction of another foreign species as a control agent. Specifically, we will examine the potential control systems using the following criteria: (1) ability to control the invasive species; (2) feasibility and cost; and (3) direct and indirect negative impacts. Finally, we will propose a comprehensive strategy for each organization moving forward, allowing for increased community collaboration and, ideally, the elimination and/or control of the invasive species.