Lespedeza cuneata
(sericea lespedeza)

Lespedeza cuneata is a flowering plant with a broad native range, including parts of central Asia, eastern and south eastern Asia and Australasia. It was introduced into the USA in the late 1800s and was widely planted for erosion control, mine reclamation and wildlife habitat. It proved to be an extremely aggressive invader of open areas, outcompeting native vegetation. Once established, it is very difficult to remove due to the seed bank which may remain viable for decades. L. cuneata is an invasive weed in rangelands and grasslands of the Midwest and eastern USA, listed as a noxious weed in Kansas and Colorado and on the Southeast Exotic Pest Plant Council’s List as a Category 1 species. However, L. cuneata is still valued for erosion control along roadsides and for forage, and several nurseries and seed companies still offer L. cuneata for these purposes. It is also reported in several other countries, but further information is limited. It is not present in Europe but following a pest risk analysis, it was added to the EPPO A1 List in 2019.

Lespedeza cuneata is native to parts of temperate and tropical Asia and Australasia (Harden, 2001), from Georgia and Afghanistan in the west through South Asia, to China, Japan and the Philippines and south throughout Southeast Asia to Papua New Guinea and Australia. It is reported to be a common native in Korea, but PIER (2019) report as introduced in the Bonin islands in Japan and Fiji.

The list of native range countries includes additional distribution records to those reported in the recent definitive publication on the species (EPPO, 2019), adding China, Georgia, Myanmar, North Korea and Papua New Guinea, sub-national records for India and Indonesia and an additional introduced record for Fiji (Flora of China Editorial Committee, 2019; ILDIS, 2017; PIER, 2019).

Lespedeza cuneata has been introduced into South Africa, Canada, USA, Mexico, Dominican Republic, Brazil, Fiji and Hawaii, but there is limited further information on its occurrence outside of the USA.

An Australian/New Zealand Weed Risk Assessment adapted for Hawaii was undertaken in 2004 as reported by PIER and gave a high risk score of 17 (Daehler, 2004).

In the USA, the plant is a declared noxious weed in Kansas (Ohlenbusch et al., 2001), Nebraska (Nebraska Department of Agriculture, 2019), Colorado (USDA-NRCS, 2019) and New York State (New York State Department of Environmental Conservation, 2014).

In 2016, L. cuneata, was identified as a priority for risk assessment within the requirements of Regulation 1143/2014 of the European Parliament (Branquart et al., 2016; Tanner et al., 2017) and a subsequent pest risk analysis concluded that L. cuneata had a moderate phytosanitary risk to the endangered area (EPPO, 2018) and was added to the EPPO A1 List (No. 426) in 2019.

In its native range in the Philippines, L. cuneata occurs on grassy slopes from altitudes of 1200-2200 m and in Taiwan it is common in open locations (roadsides, waste land, hill sides) up to altitudes of 3100 m (Mosjidis, 2003).

Where it has been introduced in the USA, L. cuneata can grow in a variety of habitats, including severely eroded sterile soils, and it will invade open woodlands, fields, prairies, the borders of ponds and swamps, meadows and open disturbed ground (Mosjidis, 2003). Weber (2017) and Gucker (2010) report that typical invaded habitats include grassland, woodland, forests, wetland edges, pastures and disturbed sites, as well as along roadsides, drainage areas, fence rows and in other disturbed areas in the USA, flourishing where other plants have difficulty growing, such as on eroded, infertile soils. It is also often found as a weed in cultivated areas, fallow and abandoned fields, meadows and marshes (Holm et al., 1979). It is also found in the dense shade of pine forests in coastal Louisiana (Pitman, 2006).

Ecological niche modelling has also been used for predicting the geographic course of L. cuneata invasions in North America and the geographic invasive potential was well predicted holding promise for the development of control and eradication strategies and for risk assessment (Peterson et al., 2003).

Genetics

Lespedeza cuneata has a chromosome count of 2n=20 (Missouri Botanical Garden, 2019). It was found to be able to produce viable hybrids with L. latissima, L. inschanica and L. hedysaroides, but no viable hybrids were obtained from crosses between perennial American and Asian species, between perennial and annual Lespedeza species, or between species with different chromosome numbers (Daehler, 2004).

Reproductive Biology

The primary mode of reproduction in L. cuneata is by seed, but spread by vegetative reproduction has also been reported (Daehler, 2004).

Flowers are of two types, with self-fertilized chasmogamous (petaliferous) flowers and cross-fertilized cleistogamous (apetalous) flowers. The primary pollinator is the honey bee (Daehler, 2004). L. cuneata is a prolific seed producer, with individual stems able to produce in excess of 1000 seeds, with 130-390 kg of seed produced per acre (325-975 kg/ha) and 770,000 seeds/kg (Ohlenbusch et al., 2001). Seed yields are highest if no biomass is removed from the plant such as by grazing, cutting, or burning during the year of seed harvest (Adamson and Donnelly, 1973). Seeds can be produced in the first year of growth, and were found to be produced from as early as 15 weeks old in Oklahoma (Farris, 2006). Seed are estimated to be able to survive for more than 20 years in the soil, although Ohlenbusch et al. (2001) noted that no direct data was available to confirm this expectation. Inferences have been made about seed banks from field studies; L. cuneata seed was found in 80–90% of soil samples from restored forest on coal mine spoil, although plants were only present in two of four plots (Carter and Ungar, 2002) and Honu et al. (2009) found 160 seeds/m² from a forest plot in Illinois where the plant was not found.

In a study that compared L. cuneata with five native species, Woods et al. (2009) found that it produced a mean of five times as many seeds and a significantly greater number of vegetative buds than any native studied and over 20 times as many flowers. L. cuneata also relied less on selfing than native species and it was concluded that the diverse reproductive biology and wide regeneration niche of L. cuneata in relation to its native facilitates its successful spread under a wide range of conditions.

Physiology and Phenology

Lespedeza cuneata can reach a height of two meters in loamy soils and has an extensive taproot that can extend up to 120 cm or more with numerous lateral branches and finer fibrous roots (Guernsey, 1977; Ohlenbusch et al., 2001). Juvenile plants have only one stem that can have many top branches. In winter, food reserves are stored in the underground taproot and old stems die back. New stems arise from root crown buds in early spring and increasing numbers of stems are produced each year. A single plant is able to form a large stand that can live over 20 years. Daylengths of 13 h or less are required for L. cuneata to flower (Mosjidis, 2003). In the USA, L. cuneata has been observed flowering from July to October (Daehler, 2004).

Longevity

Lespedeza cuneata is an aggressive, warm-season, long-lived perennial legume (Stevens, 2019)

Activity Patterns

The frequency of native insect herbivores was found to mediate the interactive effects of propagule supply and resources on the invasion of L. cuneata in the USA (Sanders et al., 2007).

Also, by comparing an ancestral L. cuneata genotype introduced to North America in 1930 with modern-day invasive (North American) and native (Japanese) genotypes, Beaton et al. (2011) found that the invasive genotype was a better competitor than either the native or the ancestral genotype, exhibiting greater induced resistance but lower constitutive resistance, suggesting that selection has played a pivotal role in shaping the species into a more aggressive, but less constitutively defended competitor.

Environmental Requirements

Lespedeza cuneata is adapted to tropical, subtropical and warm temperate areas with mean annual temperatures ranging from 10-29°C (Mosjidis, 2003). 

Pramanik and Thothathri (1983) stated that L. cuneata (as L. juncea var. sericea) is the only representative of the group occurring in both temperate and tropical climates. In the USA, it grows from Florida and Texas, north to Nebraska and east to the Atlantic coast through Michigan and New York (Ohlenbusch et al., 2001). L. cuneata can grow where annual precipitation exceeds 760 mm, but is also considered to be drought tolerant (Hoveland and Donnelly, 1985; Stevens, 2019).

Lespedeza cuneata is well adapted to clay or loam soils (Hoveland and Donnelly, 1985), but can also tolerate shallow acid soils of low fertility with a pH < 5 and high aluminium content (Cope, 1966; Plass and Vogel, 1973; Hoveland and Donnelly, 1985; Ohlenbusch et al., 2001; Mosjidis, 2003). However, L. cuneata reportedly grows best on soil with a pH of 6.0-6.5 on deep, well-drained clay or loamy soils (Ohlenbusch et al., 2001). Hoveland and Donnelly (1985) also report that the cultivar ‘Serala 76’ is better adapted to light-textured soils than the originally imported accessions.

Ohlenbusch et al. (2001) also note that the species is able to establish in dense shade, but establishes better where the competing vegetation is short and light is able to reach the ground (Ohlenbusch et al., 2001). In the USA, it was found to perform better in soil in which it had been previously grown, although the precise mechanism for this self-facilitation is not known (Coykendall and Houseman, 2014). Crawford and Knight (2017) provided evidence that effects on the soil biota were responsible, but also found that this self-facilitation was not found in competition with communities of native prairie species.

Lespedeza cuneata is a nitrogen-fixing legume, enabling its growth in nutrient-poor conditions (Brandon et al., 2004; Houseman et al., 2014). Its taproot, that can grow up to 120 cm (Guernsey, 1977; Ohlenbusch et al., 2001), contributes to its drought resistance.

Allred et al. (2010) compared morphological and physiological traits of L. cuneata with native prairie grasses in the USA and found that total and specific leaf area exceeded that of native species and may allow L. cuneata to successfully establish and dominate in tallgrass prairie, aiding in both resource acquisition and competitive exclusion. Furthermore, gas exchange traits (e.g. net photosynthesis, stomatal conductance and water use efficiency) did not exceed other species but remained constant throughout the daily sampling periods, revealing characteristics of stress tolerance. The combination of these characteristics and strategies may assist in its successful invasions in tallgrass prairie.

The following natural enemies have been reported: Acyrthosiphon pisum (pea aphid), Helicoverpa zea (American cotton bollworm), Heterodera glycines (soybean cyst nematode), Hypena scabra (green cloverworm), Lygus lineolaris (tarnished plant bug), Pratylenchus penetrans (nematode, northern root lesion) and Spissistilus festinus (three-cornered alfalfa hopper) (from data mining).

Animal feed, fodder, forage

• Fodder/animal feed
• Forage

Environmental

• Erosion control or dune stabilization
• Land reclamation
• Landscape improvement
• Revegetation
• Soil conservation
• Soil improvement

Human food and beverage

• Honey/honey flora

Lespedeza cuneata can be distinguished by leaf shape, flower colour and by its general growth form. When mature, L. cuneata is the only species within the genus that has cuneate or wedge-shaped leaf bases and flowers that are creamy-white with purple throats and numerous tall, coarse stems that grow in bunches. Juveniles of L. cuneata can be distinguished from the native and closely related L. virginica by the large coarse stems, versus few weak stems in L. virginica (Stevens, 2019).

Lespedeza cuneata has trifoliate leaves that are denser along the stem than those of L. junceasensu strictu (Pramanik and Thothathri, 1983). A key feature for distinguishing L. cuneata from L. juncea s.s. is the length to width ratio of the leaflets (Pramanik and Thothathri, 1983; Flora of China Editorial Committee, 2019), with L. cuneata having narrower leaflets with length:width ratios between 4:1 and 6:1, while the length:width ratios of L. juncea s.s. leaves are between 3:1 and 4:1.

Due to the variable regulations around (de)registration of pesticides, your national list of registered pesticides or relevant authority should be consulted to determine which products are legally allowed for use in your country when considering chemical control. Pesticides should always be used in a lawful manner, consistent with the product's label.

Cultural Control and Sanitary Measures

Rangelands can be managed by burning, grazing and fertilization. Prescribed burning of native grass in the late spring followed by intensive grazing with mature cattle will increase utilization of L. cuneata, and grazing infested sites with sheep and goats will provide effective control. Pastures should be properly fertilized and grazed during April and May (PIER, 2019). Furthermore, Lemmon et al. (2017) showed that intensive late-season grazing with sheep in native tallgrass prairie provided comprehensive control of L. cuneata in Kansas.

Fire has been used on non-rangeland infestations with some success, though results vary. Wong et al. (2012) found that controlled burns are likely to encourage spread of L. cuneata and are unlikely to effectively control the species. However, other found success with late spring burns (mid-May to the end of June) may be effective if a fire will carry through the area at that time. However, spring burning was not always effective as new shoots sprout almost immediately after fire and controlled burns in the dormant season can even promote L. cuneata as fire scarifies seeds, promoting germination and seedling establishment on open ground. Seed dormancy is broken by prescribed burning and resulting seedlings may be less viable. The persistent, long-lived seed bank may add new plants to the site for years to come, so burning can been advantageous in promoting seed germination, if followed with mechanical or chemical treatments (Stevens, 2019). Late summer burns can also decrease adult plant vigour, removing seeds from that year and decrease seedling survival (PIER, 2019). Patch burning was also found to reduce the rate of invasion by maintaining young, palatable plants in the burnt patch and could play a vital role in an integrated weed management strategy on rangelands (Cummings et al., 2007).

Mechanical Control

The deep root system makes removal of the plant by digging or pulling extremely difficult, and mowing or ploughing are generally not feasible over extensive areas as L. cuneata typically grows in rough, rocky land. Such cutting may also greatly disturb native plant populations (Stevens, 2019). Mowing plants in the flower bud stage for 2-3 years can reduce plant vigour and control further spread and good control can be achieved by mowing followed by herbicide treatment in early to mid-summer (PIER, 2019).

Chemical Control

Most current management procedures require the use of herbicides to control the growth and expansion of L. cuneata, using metsulfuron methyl, triclopyr, clopyralid and glyphosate, applied in early to mid-summer during the flower bud stage and triclopyr or clopyralid during the vegetative stage prior to branching or during flowering (PIER, 2019). In wet sites, glyphosate is effective from early summer until seed set (PIER, 2019). L. cuneata is not susceptible to 2,4-D, picloram and dicamba.

Koger et al. (2002) also found that fluroxypyr, metsulfuron and triclopyr were all effective in controlling L. cuneata in Oklahoma, but regardless of rate, triclopyr and fluroxypyr provided the most consistent long-term control. Farris and Murray (2009) found triclopyr, metsulfuron-methyl, glyphosate and 2,4-D amine plus picloram, gave greater than 80% control, but that triclopyr was the most effective with 100% control.

Repeated treatments are also required, with Gibson et al. (2019) finding that five treatments including triclopyr and fluroxypyr all reduced the abundance of L. cuneata, but that dominance returned after 3 years.

Biological Control

Schutzenhofer and Knight (2007) simulated herbivory on L. cuneata and created stage-structured projection models to determine if augmented herbivory by a leaf-chewing biological control agent would regulate population growth rate. They found that augmented herbivory influenced stage transitions in the smallest stage class causing higher mortality and reduced growth, but with no other effects on stage transitions or fecundities, despite manipulation of herbivory at exceptionally high levels (up to 80% leaf loss). They concluded that biological control by a leaf chewing herbivore would not likely be successful even if an exceptionally large amount of each plant were consumed.

Integrated Pest Management

Lespedeza cuneata is best controlled by an integrated management approach that combines mechanical, chemical and cultural methods. Mapping was also effective using hyperspectral imagery (Wang et al., 2008). To maximize success of control treatments, Emry et al. (2011) recommended that managers should explicitly consider detectability, especially where small patches are scattered throughout a site and that to quantify the probability of detection, managers should conduct multiple surveys to help determine the effort needed for effective control.

In addition, an experiment in Kansas (Foster et al., 2015) showed that ecological restoration increased plant diversity, increased above ground productivity, reduced the availability of light, soil moisture and bare soil microsites and strongly suppressed the invasion of all species including L. cuneata, whereas in the absence of restoration, L. cuneata rapidly dominated plots where it had been sown, particularly at the highest propagule pressure.

05/01/20 Original text by:

Nick Pasiecznik, Consultant, France