Lepidium Latifolium Research Articles

Control of Lepidium latifolium (perennial pepperweed) and recovery of native plants in tidal marshes of the San Francisco Estuary

Several management techniques are effective in controlling Lepidium latifolium (perennial pepperweed) in rangelands and hay meadows; however, this invader’s rapid spread into sensitive aquatic habitats throughout the western US calls for alternative control strategies. To evaluate control methods for use in tidal marshes of San Francisco Estuary, we tested chemical, mechanical, and biological methods in field and greenhouse experiments. In a field experiment in three brackish marshes spanning the estuary, application of the herbicide glyphosate to re-growth of L. latifolium following hand-removal reduced L. latifolium cover by an average of 80% after 2 years and led to a 60% increase in native vegetation cover. Glyphosate alone was less effective at reducing L. latifolium cover (20% decrease) and increasing native cover (34% increase). Preliminary tests of a potential biological control, a native parasitic plant, were not successful, thus plots intended for field trials were instead used to test the newly approved herbicide imazapyr, which showed promise in controlling L. latifolium. An additional greenhouse experiment found large reductions in stem lengths with either glyphosate following clipping or imazapyr with or without clipping, all significantly more so than glyphosate alone. We conclude that an integrated management approach of applying glyphosate following mechanical removal can be effective at reducing L. latifolium cover and allowing recovery of native tidal marsh plants, providing a useful solution for controlling smaller, accessible infestations of the invader. Our preliminary tests of imazapyr suggest that it may be very effective at controlling L. latifolium in tidal marshes, although further assessment of non-target effects and native plant recovery are needed to evaluate its relative merit.

Tolerance and recovery responses of playa halophytes to light, salinity and temperature stresses during seed germination

Halogeton glomeratus (M. Bieb.) C.A. Mey., Lepidium latifolium Linn. and Peganum harmala Linn. are distributed in temperate salt playa habitats of Upper Hunza, Pakistan. Seeds were germinated under various salinity (0–500 mM NaCl), light (12 h-light:12 h-dark and 24 h-dark) and temperature (5/15, 10/20, 15/25, 20/30, and 25/35 °C, dark/light) regimes for 20 days to determine the optimal conditions for germination and recovery of seeds from these factors when exposed to less than optimal conditions. Seeds that failed to germinate in dark were transferred successively to 12 h-photoperiod, salinity to distilled water and from various temperature regimes to 20/30 °C, to determine the effect of these stresses and the ability of these seeds to recover respectively. Highest seed germination ( H. glomeratus and L. latifolium: 100%; P. harmala: 80%) was obtained in non-saline control at 20/30 °C in 12 h-photoperiod, however, increase in salinity progressively inhibited seed germination. Seed germination of H. glomeratus and P. harmala was substantially inhibited and that of L. latifolium was prevented in dark. Salinity and dark treatments have a synergistic effect in inhibiting seed germination of all species. No seed of any species germinated at 5/15 °C; germination was substantially inhibited at 25/35 °C both for H. glomeratus and P. harmala while L. latifolium failed to germinate at 25/35 °C. Rate of germination also decreased with an increase in salinity at all temperature regimes but this effect was minimal at optimal temperature regime of 20/30 °C. After successive elimination of light, salinity and temperature stresses, final seed germination was identical to respective controls. The results indicate that seeds of these temperate halophytes could endure environmental stresses without losing viability and germinate readily when these stresses are removed. Under the extremely variable conditions of the playa habitat these species are highly opportunistic exploiting the windows of opportunity available during spring or early summer.

The effects of temporally variable dispersal and landscape structure on invasive species spread

Many invasive species are too widespread to realistically eradicate. For such species, a viable management strategy is to slow the rate of spread. However, to be effective, this will require detailed spread data and an understanding of the influence of environmental conditions and landscape structure on invasion rates. We used a time series of remotely sensed distribution maps and a spatial simulation model to study spread of the invasive Lepidium latifolium (perennial pepperweed) in California's Sacramento-San Joaquin River Delta. L. latifolium is a noxious weed and exhibited rapid, explosive spread. Annual infested area and empirical dispersal kernels were derived from the remotely sensed distributions in order to assess the influence of weather conditions on spread and to parameterize the simulation model. Spread rates and dispersal distances were highest for nascent infestations and in years with wet springs. Simulations revealed that spread rates were more strongly influenced by the length of long-distance dispersal than by temporal variation in its likelihood. It is thus important to capture long-distance dispersal and the conditions that facilitate spread when collecting data to parameterize spread models. Additionally, management actions performed in high-spread years, targeting long-distance recruits, can effectively contain infestations. Corridors were relatively unimportant to spread rates; their effectiveness at enhancing rate of spread was limited by the species' dispersal ability and the time needed to travel through the corridor. In contrast, habitat abundance and shape surrounding the introduction site strongly influenced invasion dynamics. Satellite patches invading large areas of invasible habitat present especially high risk.

Rangeland Invasive Plant Management

lands provide a valuable resource for wildlife and recreational activities, as well as livestock grazing. The establishment and spread of invasive plants on rangeland are often symptomatic of long-term cultural practices.3 Invasion of many rangeland sites by non-native plants has been facilitated by multiple factors including overgrazing by domestic livestock, purposeful introduction of non-native plants for agricultural purposes, unintentional introduction of non-native plant seeds as a contaminate in crop seed, changes in fire frequency and intensity, and climatic changes that converge to cause shifts in plant community composition. There are over 300 rangeland weeds in the United States, but perhaps 30 have significant negative impact in the western United States.2 Of these, some of the most problematic include downy brome or cheatgrass {Bromus tectorum), medusahead {Taeniatherum caput-medusae), leafy spurge {Euphorbia esula)> perennial pepperweed {Lepidium latifolium), Dalmatian toadflax {Linaria dalmatica), and several members of the Asteraceae, including yellow starthistle {Centaurea solstitialis), diffuse knapweed (C. diffusa), spotted knapweed {C. stoebe subsp. micranthos), musk thistle {Carduus nutans), Canada thistle {Cirsium arvense), hawkweeds {Hieracium spp.), and Russian knapweed {Acroptilon repens). These and other invasive plants can have adverse effects on rangeland and pastures by disrupting vegetation dynamics and reducing ecosystem capacity to recover after disturbance.3 The financial impacts of invasive plants in rangelands are substantial and have been estimated to cost ranchers US$5 billion annually just for control.4 Other impacts to the livestock industry not included in the estimate are the negative effects of invasive plants on yield and quality of forage, livestock poisoning, interference with grazing, supplemental costs associated with managing and producing livestock, and land values. In addition to the livestock industry, invasive rangeland species can decrease wildlife habitat and forage, deplete soil and water resources, and reduce plant and animal diversity. Mechanical, cultural, biological, and chemical methods have been developed to manage rangeland invasive plants. These methods include mowing, prescribed burning, appropriate grazing management, herbicides, biocontrol agents, and revegetation with desirable plants.1 The merits of each control measure and potential for complementary or synergistic interactions when applied in appropriate sequences and combinations should be considered when developing integrated weed management programs. For example, summer burning resulted in a dramatic increase in yellow starthistle germination the following fall and winter.5 Thus, using an herbicide treatment in the year following a prescribed burn gave far better control of yellow starthistle compared with an herbicide treatment followed by prescribed burning. Successful integrated strategies require careful planning that incorporates a long-term approach consisting of prevention programs, education activities, and management approaches. These are designed to diminish negative impacts of invasive plants by improving the invaded plant community to increase its ecosystem function, niche occupation, and competitiveness. These qualities can increase the communities' resistance to reinvasion by other invasive plants.3

Effects of microtopography and hydrology on phenology of an invasive herb

Phenological traits may influence invasion success via effects on invasiveness of the colonizing species and invasibility of the receiving ecosystems. Many species exhibit substantial fine‐scaled spatial variation in phenology and interannual differences in phenological timing in response to environmental variation. Yet describing and understanding this variation is limited by the availability of appropriate spatial and temporal datasets. Remote sensing provides such datasets, but has primarily been used to monitor broad‐scale phenological patterns at coarse resolutions, necessarily missing fine spatial detail and intraspecies variation. We used hyperspectral remote sensing to characterize the spatial and temporal phenological variation of the invasive species Lepidium latifolium (perennial pepperweed) at two sites in California's San Francisco Bay/Sacramento–San Joaquin River Delta. Considerable phenological variation was detected: L. latifolium was simultaneously present in vegetative, early flowering, peak flowering, fruiting, and senescent stages in late June; the relative dominance and distribution of these stages varied interannually. Environmental determinants of phenology were investigated with variables derived from the hyperspectral image data, from a high resolution LiDAR (light detection and ranging) digital elevation model (DEM), and from local precipitation and streamflow data. Lepidium latifolium phenology was found to track water availability, and may also be influenced by intraspecific competition and edaphic stress. Lepidium latifolium has a unique phenology (summer flowering) relative to the communities it invades, which may allow invasion of an empty niche. Furthermore, many habitats are invaded by L. latifolium, which occurs in locally appropriate phenologies under the different environmental conditions. The environmental responsiveness of L. latifolium phenology may mediate the wide breadth of invasible habitats.

Isolation of cold stress-responsive genes from Lepidium latifolium by suppressive subtraction hybridization

Suppression subtraction hybridization (SSH) libraries were constructed from RNA isolated from leaves of control and cold stress-induced Lepidium latifolium, a cold-tolerant plant species from high altitudes for isolation of cold-responsive genes. A total of 500 clones were obtained from the cold stress library. Dot blot expression analysis identified 157 clones that were upregulated and 75 that were downregulated during cold stress. These clones selected on the basis of their expression patterns on dot blot were sequenced. As much as 27 and 17 genes were identified from the forward and reverse libraries, respectively. The genes identified revealed homology with genes involved in diverse processes such as gene regulation/signaling, photosynthesis, DNA damage repair protein, pathogenesis-related protein, senescence-associated proteins and proteins with unknown functions.

Predicting the Distribution of Perennial Pepperweed (Lepidium latifolium), San Francisco Bay Area, California

AbstractPerennial pepperweed is an invasive plant species that occurs throughout the western United States. This study develops a predictive model for perennial pepperweed distribution for the San Francisco Bay Area, based on spatial variables. Distribution data were developed by mapping perennial pepperweed along the shoreline of the South San Francisco Bay, using geographic positioning system units. Spatial relationships between its distribution and spatial variables were tested using binomial logistic regression. Predictive models were mapped using geographic information systems (GIS), and high risk areas within the San Francisco Bay Area were identified. Perennial pepperweed was found to occur within marsh habitats with full tidal action and near open water. This study demonstrates that habitat variables from widely available GIS layers can be used to predict distribution patterns for perennial pepperweed. The model results were compared to land ownership within the study area to demonstrate a management application of the model.

Black Greasewood (Sarcobatus vermiculatus), Gray Rabbitbrush (Ericameria nauseosa), and Perennial Grass Response to Chlorsulfuron and Metsulfuron

AbstractBlack greasewood (greasewood) and gray rabbitbrush are important shrub components of several plant communities throughout western North America. Land managers may view these species differently depending on their goals. Greasewood and gray rabbitbrush shrub communities may be invaded by several invasive plants including Russian knapweed, perennial pepperweed, hoary cress, halogeton, and several annual mustards. Metsulfuron and chlorsulfuron are commonly used for controlling these and other invasive plants, but little is known regarding their impacts on greasewood and gray rabbitbrush. Our objective was to quantify the impact of these herbicides on greasewood and gray rabbitbrush communities from both an efficacy and nontarget impact perspective. Field studies were established in the spring of 2004 and repeated twice in 2005 near Laramie, WY, in a pasture with mixed stands of greasewood and gray rabbitbrush. Treatments included metsulfuron applied at 21, 42, 63, 84, 126, and 168 g ai/ha (0.3, 0.6, 0.9, 1.2, 1.8 and 2.4 oz ai/A), chlorsulfuron applied at 52, 105, and 157 g ai/ha (0.75, 1.5 and 2.25 oz ai/A), and an untreated control. All treatments contained methylated seed oil at 2% v/v. Treatments were applied in mid-June to 3.3 by 9-m (10 by 30 ft) plots with a handheld broadcast sprayer delivering 187 L/ha (20 gal/ac) in a randomized complete block, with three blocks per study. Plots were sampled 12 and 24 mo after treatment (MAT), utilizing visual control estimates and point frame sampling for vegetative cover of greasewood, gray rabbitbrush, perennial grasses, and bare ground. Metsulfuron at 42 g/ha and chlorsulfuron at 105 g/ha provided > 75% visual control of greasewood 24 MAT. For gray rabbitbrush, metsulfuron at 63 g/ha provided approximately 60% control 24 MAT, while chlorsulfuron provided negligible control at any rate. These results suggest differential impacts of these herbicides on greasewood and gray rabbitbrush, and provide land managers with a decision tool for noxious and invasive weed control when managing for or against greasewood and gray rabbitbrush.

Habitat suitability modelling of an invasive plant with advanced remote sensing data

AbstractAim Lepidium latifolium (Brassicaceae; perennial pepperweed) is a noxious Eurasian weed invading riparian and wetland areas of the western USA. Understanding which sites are most susceptible to invasion by L. latifolium will allow more efficient management of this weed. We assessed the ability of advanced remote sensing techniques to develop habitat suitability models for L. latifolium.Location San Francisco Bay/Sacramento‐San Joaquin River Delta, California, USA.Methods Lepidium latifolium distribution was mapped with hyperspectral image data of Rush Ranch Open Space Preserve, providing presence/absence data to train and validate habitat models. A high‐resolution light detection and ranging digital elevation model was used to derive predictor environmental variables (distance to channel, distance to upland, elevation, slope, aspect and convexity). Aggregate decision tree models were used to predict the potential distribution of this species.Results Lepidium latifolium infested two zones: near the marshland–upland margin and along channels within the marsh. Topographical data, which are typically strongly correlated with wetland species distributions, were relatively unimportant to L. latifolium occurrence, although relevant microtopography information, particularly relative elevation, was subsumed in the distance to channel variable. The map of potential L. latifolium distribution reveals that Rush Ranch contains considerable habitat that it is susceptible to continued invasion.Main conclusions Lepidium latifolium invades relatively less stressful sites along the inundation and salinity gradients. Advanced remote sensing datasets were shown to be sufficient for species distribution modelling. Remote sensing offers powerful tools that deserve wider use in ecological research and management.

Lepidium latifolium reproductive potential and seed dispersal along salinity and moisture gradients

Lepidium latifolium is an aggressive plant species that is invading both wetlands and uplands across a wide range of salinities. This study examined how salinity and moisture gradients influence the potential for invasion by L. latifolium. Three sites in the San Francisco Bay Delta with varying salinity and moisture levels were chosen as research sites. These sites corresponded to a dry (18.32%) freshwater (3.88‰) site, a wet (40.53%) brackish (23.16‰) site, and a moderately wet (38.33%) saline (32.33‰) site. Our results showed that inflorescence number and height were unaffected by salinity or soil moisture. Seed production was significantly affected by salinity (P = 0.0297) and moisture levels (P = 0.0004). Seed production at the high salinity site was reduced by 29% from the freshwater site. Seed production at the wettest site had an 87% reduction from the driest site. Seed viability was also reduced by both salinity (P < 0.0001) and soil moisture (P < 0.0001). Viability at the highest salinity site was reduced by 49% from freshwater sites and was reduced by 8% from the wettest to driest sites. Mean seed dispersal distance was 0.23 m greater at the freshwater site, which was not statistically significant (P = 0.1815). The deleterious effects of salinity and moisture resulted in reduced L. latifolium densities in high salinity and moisture locations, but only at the highest salinity site. With increased seed production and viability, drier freshwater sites experience greater propagule pressure, resulting in an increased invasion potential. Therefore, variability along salinity and soil moisture gradients serve as useful metrics for prioritizing control and eradication efforts of L. latifolium.

The role of environmental context in mapping invasive plants with hyperspectral image data

Lepidium latifolium (perennial pepperweed) is a noxious Eurasian weed invading riparian and wetland areas of the western US. Effective management of Lepidium requires detailed, accurate maps of its distribution, as may be provided by remote sensing, to contain existing infestations and eradicate incipient populations. We mapped Lepidium with 3 m spatial resolution, 128-band HyMap image data in three sites of California's San Francisco Bay/Sacramento–San Joaquin Delta Estuary (Rush Ranch in Suisun Marsh and the Greater Jepson Prairie Ecosystem and the Cosumnes River Preserve in the Delta). These sites are markedly different in terms of hydrology, salinity, species composition, and structural and landscape diversity. Aggregated classification and regression tree models (CART), incorporating the results of mixture tuned matched filter (MTMF) analyses and spectral physiological indexes, were used to map Lepidium at the three sites. This approach was sufficiently flexible and robust to detect Lepidium with similar accuracies (~ 90%) at both Rush Ranch and Jepson Prairie, but was unsuccessful at Cosumnes River Preserve. Comparisons of the behavior of the MTMFs and the CARTs between sites reveal the importance of environmental context in species mapping. Rush Ranch presents the simplest conditions for mapping Lepidium: it is the wettest and least diverse site and Lepidium is spectrally distinct from co-occurring species. At Jepson Prairie, several co-occurring species closely resemble Lepidium spectrally. Nevertheless, hyperspectral data provide sufficient spectral detail to resolve Lepidium even at this challenging site, which is facilitated by phenological separation from the matrix of annual grasses. At Cosumnes River Preserve, however, Lepidium is neither spectrally nor phenologically distinct, and consequently could not be mapped successfully. Evidence suggests that the success of a remote sensing analysis declines as site complexity increases (species, structural, and landscape diversity; spectral variability; etc.), although this relationship is complex, indirect, and may be phenology-dependent.

Identification of invasive vegetation using hyperspectral remote sensing in the California Delta ecosystem

Estuaries are among the most invaded ecosystems on the planet. Such invasions have led in part, to the formation of a massive $1 billion restoration effort in California's Sacramento–San Joaquin River Delta. However, invasions of weeds into riparian, floodplain, and aquatic habitats threaten the success of restoration efforts within the watershed and jeopardize economic activities. The doctrine of early detection and rapid response to invasions has been adopted by land and water resource managers, and remote sensing is the logical tool of choice for identification and detection. However meteorological, physical, and biological heterogeneity in this large system present unique challenges to successfully detecting invasive weeds. We present three hyperspectral case studies which illustrate the challenges, and potential solutions, to mapping invasive weeds in wetland systems: 1) Perennial pepperweed was mapped over one portion of the Delta using a logistic regression model to predict weed occurrence. 2) Water hyacinth and 3) submerged aquatic vegetation (SAV), primarily composed of Brazilian waterweed, were mapped over the entire Delta using a binary decision tree that incorporated spectral mixture analysis (SMA), spectral angle mapping (SAM), band indexes, and continuum removal products. Perennial pepperweed detection was moderately successful; phenological stage influenced detection rates. Water hyacinth was mapped with modest accuracies, and SAV was mapped with high accuracies. Perennial pepperweed and water hyacinth both exhibited significant spectral variation related to plant phenology. Such variation must be accounted for in order to optimally map these species, and this was done for the water hyacinth case study. Submerged aquatic vegetation was not mapped to the species level due to complex non-linear mixing problems between the water column and its constituents, which was beyond the scope of the current study. We discuss our study in the context of providing guidelines for future remote sensing studies of aquatic systems.

Two New Naturalized Species From Korea, Carduus natans and Lepidium Latifolium

Two naturalized species, Carduus natans L. and Lepidium latifolium L. were newly reported from Korea. Carduus natans, Sa-hyang-ung-gung-kwi, was found from Nanjido, Seoul, and Yangsuri and Naejangri, Gyunggi-do. It is distinguished from widely naturalized C. crispus by having large nodding heads (30-60mm in diameter) and acuminate lanceolate involucral bracts. Lepidium latifolium, Keun-ki-da-dag-naeng-i, was found from Noeul Park, Nanjido, Seoul. It is distinguished from the related species by having tall height (about 1 m), subsessile upper leaves, pinnately lobed lower leaves, and corymbose inflorescence.

Integrated Management of Perennial Pepperweed (Lepidium latifolium)

AbstractPerennial pepperweed is invasive throughout California. It thrives in a wide range of environments and is a common weed in floodplains, pastures, wetlands, and roadsides. In disturbed areas, perennial pepperweed rapidly forms monotypic stands with a thick litter layer. These infestations not only out-compete other vegetation, but prevent re-establishment of desirable species even after perennial pepperweed control. This experiment examined integrated management strategies with the goal of maximizing perennial pepperweed control and establishment of desirable native vegetation. The experiment was conducted at two sites in Lassen County, CA. Both sites were heavily infested with perennial pepperweed and lacked competing vegetation. The experimental design was a split-split-randomized block with four replications. Site preparation treatments included winter burning, summer and fall mowing, winter grazing, and fall disking. These treatments were designed to remove thatch to facilitate herbicide application and reseeding of desirable perennial grasses. Herbicide treatments included chlorsulfuron, 2,4-D, or glyphosate applied at the flower bud stage. Revegetation treatments included no seeding and no-till seeding of native perennial grasses. Most site preparation plus herbicide combinations reduced perennial pepperweed cover &gt; 85% compared to the untreated control, although treatment efficacy was variable between sites and years. Burning, grazing, mowing, or disking in combination with herbicide treatment and no-till seeding was necessary for successful native perennial grass establishment. Burning or mowing with yearly 2,4-D applications for 3 yr gave the best combination of perennial pepperweed control and native grass establishment. Chlorsulfuron caused chlorosis and stunting to western wheatgrass, basin wildrye, and beardless wildrye at both sites when applied the spring before seeding. No treatment offered complete weed control, suggesting follow-up spot herbicide applications are needed for long-term perennial pepperweed suppression. These results provide several successful integrated strategies for control of perennial pepperweed and revegetation to a desired native perennial grass community.

True Metabolizable Energy for Seeds of Common Moist‐Soil Plant Species

Abstract: Understanding the true metabolizable energy (TME) value of food is important for constructing bioenergetic models. We estimated gross energy, nutrient composition, and TME values for the seeds of 3 native and 1 invasive exotic wetland plant that occur in the diet of waterfowl. True metabolizable energy values were 0.50 ± 0.080 kcal/g for spike rush (Eleocharis palustris), 0.65 ± 0.080 kcal/g for alkali bulrush (Schoenoplectus maritimus), 1.31 ± 0.090 kcal/g for perennial pepperweed (Lepidium latifolium), and 2.52 ± 0.080 kcal/g for lamb's quarters (Chenopodium album). The TME value for 3 of 4 species, including the invasive species, was low relative to the TME value of other seeds consumed by waterfowl.

The Biology of Invasive Alien Plants in Canada. 8. Lepidium latifolium L.

The cruciferous weed Lepidium latifolium, perennial pepper-grass, is a relatively recent immigrant with a disjunct distribution in North America. Although first reported in the 1930s in Quebec and 1940s in Alberta, L. latifolium only started to attract attention as an invasive weed when it began to spread rapidly in the western parts of its US range in the 1980s, reaching British Columbia in the 1990s. Lepidium latifolium is a perennial weed of coastal wetlands, inland waterways, irrigation ditches, rangeland, hay meadows and waste areas, and tolerates saline/alkaline environments. Prolific seed production, rapid and substantial vegetative growth, creeping rhizomes with high storage capacity, potential for bud production at each node, and deep rhizome penetration have contributed to the widespread establishment of L. latifolium. Canopy height and density, combined with an accumulation of dead stalks in wetlands, has interfered with the regeneration of native plants and the habitats of birds and other animals, as well as hampering control of mosquitoes. In rangelands and pastures, L. latifolium can compete with native species and reduce forage quality. Lepidium latifolium has recently invaded agricultural crops such as cereal grains and alfalfa, and can contaminate hay shipments. Decaying litter may increase sodium content in surface soil, with a potential negative impact on salt-intolerant species. Lepidium latifolium has few natural enemies in North America. It has been partially controlled by flooding, intensive grazing, mowing and herbicides, but herbicides are of restricted use along waterways and in areas with native vegetation. Potential biological controls have shown little promise to date. Key words: Lepidium latifolium, perennial pepper-grass, perennial pepperweed, lépidie à feuilles larges, LEPLA, weed biology, invasive alien

Spectral and physiological uniqueness of perennial pepperweed (Lepidium latifolium)

Abstract Perennial pepperweed is an aggressive, exotic weed invading wetland and riparian areas in California, including the San Francisco Bay/Sacramento–San Joaquin Delta Estuary. Effective management will require detailed and accurate maps of its distribution. Remote sensing technologies offer the capability to map weed species over broad areas and with rapid return intervals. As a first step in assessing the potential to map perennial pepperweed with hyperspectral remote sensing data, this study determined its spectral uniqueness relative to co-occurring species. Spectral measurements were conducted during summer drought conditions in the Sacramento–San Joaquin Delta region. Reflectance spectra of perennial pepperweed and seven co-occurring species were collected with a portable spectrometer. Nineteen physiological indexes were calculated from the reflectance data. Physiological indexes are sensitive to narrow spectral features and encapsulate reflectance information in ecologically relevant ways. Clas...

Natural history, distribution, and management of Lepidium latifolium (Brassicaceae) in New England

Abstract Lepidium latifolium (perennial pepperweed) is an herbaceous perennial, native to Europe and western Asia, that is now well established at many locations in Massachusetts and Connecticut. This species is considered a major invasive species in the western United States and appears likely to become invasive in the east if left unchecked. We showed that the distribution is greater than previously documented in New England and that populations appear to be expanding. Individuals of the species can produce thousands of seeds and we found that these seeds are tolerant to many days of inundation by salt water so that dispersal by tidal and river currents is likely. In addition, populations can expand at least 2 m/yr from growth by rhizomes, and densities exceeded 50 shoots/m2 in some areas. We identified 17 species of plants that are likely impacted by the expanding populations and 23 families of arthropods associated with L. latifolium in some of these areas. In wetland habitats, repeated pulling of sho...

Early Season Mowing Improves the Effectiveness of Chlorsulfuron and Glyphosate for Control of Perennial Pepperweed (Lepidium latifolium)

Perennial pepperweed is an invasive weed spreading rapidly throughout a wide range of habitats in the western United States. This study was designed to test whether integrating early season mowing with a systemic herbicide application would improve the control of perennial pepperweed. Experiments were conducted within three different environments including high desert, roadside, and floodplain areas. In treatments not mowed, chlorsulfuron at 0.104 kg ai/ha reduced perennial pepperweed biomass and density by 100%, whereas applications of 2,4-D at 2.11 kg ae/ha and glyphosate at 3.33 kg ae/ha were inconsistent and did not provide effective control. Mowing alone did not reduce perennial pepperweed biomass or density the following year, but mowing followed by application of a herbicide treatment to resprouting plants reduced biomass at all three sites compared with nonmowed treatments including herbicides. Among combinations of mowing and herbicides, chlorsulfuron at 0.052 kg/ha reduced perennial pepperweed biomass by &gt;99% at all three sites, and glyphosate at 3.33 kg/ha reduced biomass by ≥80% at two sites 1 yr after applications. The effectiveness of glyphosate at 3.33 kg/ha in combination with mowing provides land managers with a valuable control option for perennial pepperweed in wetland or riparian areas where chlorsulfuron is not registered for use.

A new species of grassflies of the genus Lasiosina Becker from Turkey (Diptera: Chloropidae)

Lasiosina devitata sp. n. is described from Turkey. Specimens were reared from stem of Lepidium latifolium (Brassicaceae). This is the first record of the feeding of Lasiosina larvae on dicotyledon plant. Some characters are added to the description of species of the L. nigriantennata group based on examination of type specimens.