Leucaena diversifolia

L. diversifolia and its hybrid with L. leucocephala are aggressive colonizers of ruderal sites and secondary or disturbed vegetation in Mexico (the native range). According to Hughes (1998b), L. diversifolia has all the invasive traits associated with L. leucocephala, e.g. precocious year-round flowering and fruiting, abundant seed production, self-fertility, hard seed coat, and ability to resprout after fire or cutting, ability to build up a seed bank. However, its invasive behaviour is much more poorly documented.

A new taxonomic monograph of the genus Leucaena has recently been completed (Hughes, 1998a) building on an earlier revision of the Mexican species (Zarate, 1994). Hughes (1998b, 1999) also discusses taxonomy and field identification of Leucaena in detail. In the past, L. diversifolia has been taken to include two subspecies corresponding to known tetraploid and diploid cytotypes (Brewbaker, 1987a; Pan and Brewbaker, 1988; Zárate, 1994; Ipor, 1997), commonly referred to as DIV4N and DIV2N, respectively. Pan (1988) postulated the tetraploid, referred to as subsp. diversifolia, to be an autotetraploid derived from the diploid taxon, referred to as subsp. trichandra (or sometimes subsp. stenocarpa by Zarate, 1994). These two subspecies are more correctly treated as separate species (Hughes, 1998a, 1999). This is based, not only on morphological differences, but also molecular evidence (Harris et al., 1994) which casts doubt on the hypothesis by Pan (1988). The narrower concept of L. diversifolia adopted by Hughes (1998a) corresponds to the tetraploid species (L. diversifolia subsp. diversifolia sensu Pan (1988) and Zarate (1994)), with the diploid taxon restored to species rank as L. trichandra. Most of the applied literature on L. diversifolia over the last two decades (for example, Ipor, 1997) refers to the broader concept of the species including both cytotypes and thus requires careful interpretation. L. diversifolia also resembles, and is closely related to, L. pulverulenta.

A full botanical description of L. diversifolia is provided by Hughes (1998a). It is a small tree, commonly reaching 3-15 m tall and 10-35 cm in bole diameter; but older trees may reach 20 m tall and 40 cm diameter. Form varies from shrubby and highly branched to more arborescent with a short clear bole to 5 m, upright angular branching and an open, rounded crown. Bark is mid grey-brown with shallow, rusty orange-brown, vertical fissures; slash reddish. Bipinnate with 16-24 pairs of pinnae per leaf and 48-58 pairs of leaflets per pinna. The leaflets are very small, 4-5.5 mm long, 0.8-1 mm wide, linear-oblong, acute at tip, strongly asymmetric, round to obtuse at base and glabrous except on margins, with a concave, cup-shaped, elliptic petiole gland. Arranged on compact globose heads, the flower heads in groups of 1-5 in leaf axils arising on actively growing young shoots, the leaves developing simultaneously with the flowers, the heads 11-15 mm in diameter with 45-90 flowers/head, the stamen filaments, anthers and style white, pale pink, sometimes bright shocking pink, and occasionally bright scarlet, anthers sparsely hairy at tip (visible with a hand lens). Hairy anthers distinguish Leucaena from all other Mimosoid legume genera. Pods 10-13 cm long, 13-16 mm wide, narrow linear-oblong and flat with papery pod walls, mid- to dark reddish-brown, glabrous and slightly lustrous, or densely covered in white velvety hairs, arranged in clusters of 1-6 per flower head.

L. diversifolia is distributed along a narrow belt at mid elevations on the moist Gulf-facing slopes of the Sierra Madre Oriental of central and southern Mexico from Hidalgo south through Veracruz, northern Oaxaca, and Tabasco to northern Chiapas, and the northern fringes of the Guatemalan Department of Huehuetenango on the wet north-facing slopes of the Sierra de los Cuchumatanes. Taxonomic confusion and mis-identification have meant that previous authors have considered L. diversifolia to be much more restricted in distribution than this, occurring only in central Veracruz, around Jalapa (Brewbaker, 1987a; Zarate, 1994). L. diversifolia and its hybrid with L. leucocephala are aggressive colonizers of ruderal sites and secondary or disturbed vegetation in Mexico.

After L. leucocephala, it is the most widely cultivated species of Leucaena (Brewbaker, 1987b; Bray and Sorensson, 1992; Brewbaker and Sorensson, 1994), based largely, until recently, on the widely distributed University of Hawaii, K156 accession from Veracruz, Mexico. L. diversifolia has been introduced outside its native range in historical times to Jamaica, Martinique (from where it was described as L. brachycarpa, see Adams, 1972), the Philippines and Papua New Guinea, usually for use as a shade tree for coffee, and much more widely in international research trials in the last two decades. Wider international planting of L. diversifolia as a reforestation species for wood and livestock fodder, especially in tropical highland areas, is being promoted with large scale seed distribution in some areas, for example Zambia.

Like the related L. leucocephala, L. diversifolia has been widely introduced ouside its native range and is the second most widely distributed Leucaena species. Although there is little specific literature relating to the invasive behaviour of this species, Hughes (1998) considered it to have "all the invasive traits of L. leucocephala" and it is therefore anticipated to be reported invasive in the future. A further risk is the tendancy of this species, like L. leucocephala, to form spontaneous hybrids (Hughes, 1998b).

No specific information on the movement and dispersal of L. diversifolia seeds is available, but it may be assumed that these are similar to those for the closely related L. leucocephala.

It is easily differentiated from the common L. leucocephala by its very small and more numerous leaflets.

L. diversifolia is a highland species, native to the humid mid-elevation flanks of the mountains of southern Mexico and northern Guatemala. L. diversifolia and its hybrid with L. leucocephala are aggressive colonizers of ruderal sites and secondary or disturbed vegetation in the native range.

GeneticsL. diversifolia is a self-compatible tetraploid of probable hybrid origin. Harris et al. (1994) showed that the most likely maternal parent species is L. pulverulenta but the paternal parent remains uncertain. Until recently, L. diversifolia was considered to occupy a restricted distribution in central Veracruz, Mexico (Brewbaker, 1987b; Pan, 1988; Pan and Brewbaker, 1988; Zarate, 1994; Ipor, 1997). Efforts to evaluate the potential of L. diversifolia were restricted to accessions collected from that restricted area, with two accessions, K156 and K784, both collected near Fortín in Veracruz, Mexico noted as outstanding. Recent taxonomic work (Hughes, 1998b) has shown that L. diversifolia is much more widely distributed than originally thought, across five States in south-central Mexico and in northern Guatemala. More comprehensive provenance seed collections sampled from across this wider distribution have now been assembled (Hughes et al., 1995; Bray et al., 1997; Hughes, 1998b), but it is too early to draw conclusions about patterns of provenance variation based on the handful of trials that include this new material.Artificial hybridization has been the main thrust of breeding efforts in Leucaena, used to overcome the limitations of L. leucocephala and its inherent lack of genetic and useful diversity (Brewbaker and Sorensson, 1990). L. leucocephala has been the most important parent in hybrid programmes. The L. leucocephala x L. diversifolia hybrid also occurs spontaneously wherever the two species are juxtaposed in cultivation, and is documented from Mexico, Guatemala, Jamaica, Martinique, the Philippines and Papua New Guinea (Hughes, 1998a, 1998b; Hughes and Harris, 1998). Hughes and Harris (1998) named it as L. xspontanea. KX3, or L. x spontanea, and like its parents, it is self-fertile, seeds copiously, is fast growing and potentially weedy (Hughes and Jones, 1999), and intermediate in psyllid resistance and fodder quality between L. leucocephala and L. diversifolia.Physiology and PhenologyL. diversifolia is self-fertile and produces prodigious quantities of seed from an early age, seasonally in the native range from April to June (Hughes, 1998a). Reproductive BiologyAs a self-compatible tetraploid, L. diversifolia sets prodigious quantities of seed from an early age and is potentially weedy (Ipor, 1997; Hughes, 1998b; Hughes and Jones, 1999). There are between 50,000 and 80,000 seed/kg. It is also one of the most important parents in spontaneous and artificial hybridization (Brewbaker and Sorensson, 1994; Sorensson and Brewbaker, 1994; Sorensson, 1995; Hughes, 1998b; Hughes and Harris, 1998; Austin et al., 1999).Environmental RequirementsOne of the most notable features of L. diversifolia is its cool tolerance compared with the pantropically planted and essentially tropical species, L. leucocephala. L. diversifolia is well adapted to cool, but frost-free, mid-elevation, tropical highland climates, and has out-yielded L. leucocephala on cool highland sites with a mean annual temperature of 16°C in Hawaii (Brewbaker, 1982; Brewbaker and Sorensson, 1987; Brewbaker et al., 1988; Austin et al., 1997), Jamaica (Adams, 1972), Zimbabwe (Maasdorp, 1992), India (Khajuria and Singh, 1991), Sri Lanka (Gunasena and Wickremasinghe, 1995) Papua New Guinea (Howcroft, 1994) and elsewhere (Ipor, 1997; Mullen et al., 1999a). In Mexico and Guatemala, the natural distribution coincides with the optimal coffee growing zone along a narrow belt, between 400 and 1500 m altitude, of moist or very moist submontane evergreen forest, subject to frequent mist and cloud cover along the Gulf-facing slopes from 16-21°N. Mean annual temperatures in these areas range from 15-21°C and rainfall from 1500 to 3500 mm with a short, 2-4 month dry season (Hughes, 1998a, b). L. diversifolia thus grows well in cool, moist, stable climates, and is ideally suited to the tropical highlands. It does not withstand frost (Williams, 1987), limiting its use in subtropical areas.Several studies have cited L. diversifolia as one of a handful of Leucaena species showing moderate acid soil tolerance compared with L. leucocephala, which grows well only on freely-drained, neutral, or slightly alkaline soils (Hutton, 1981, 1983, 1990, 1995; Oakes and Foy, 1984; Holden et al., 1988). However, most of these reports refer to the diploid cytotype, now referred to L. trichandra, rather than to the truly tetraploid L. diversifolia. Furthermore, although true L. diversifolia does show somewhat greater acid soil tolerance than L. leucocephala, there is now a general consensus that significant acid soil tolerance is likely to be difficult to achieve within Leucaena even through breeding, and that other genera such as Calliandra, Desmodium, Erythrina, Flemingia and Inga may provide better options for such areas (Blamey and Hutton, 1995; Hughes, 1998b; Mullen et al., 1999a). It is commonly found between 500 m and 2500 m altitude.AssociationsL. diversifolia has the ability to form a symbiotic association with Rhizobium root nodule bacteria, which are able to fix atmospheric nitrogen.

Lenne (1991) and Boa and Lenne (1995) reviewed pests and diseases of Leucaena. The most important pest of commercial plantings is the insect defoliator, Heteropsylla cubana. Two important diseases caused by fungal pathogens, Camptomeris leaf spot and gummosis, have been reported, and a set of lesser-known rusts and other diseases of currently minor importance are listed by Boa and Lenne (1995) and Ipor (1997). A range of seed-feeding bruchid and other beetles predate seeds of Leucaena species (Hughes and Johnson, 1996; Hughes, 1998b).The psyllid defoliator, H. cubana feeds on developing shoots and young foliage causing limited tree mortality, severe and cyclical defoliation, deformation, stunting and dieback. The psyllid is a classic example of a pest catching up with an exotic after many years of pest-free existence, through its accidental movement to a new area (Beardsley, 1986) and is spreading across Asia and Africa (Bray, 1994; Djogo, 1994; Sampet et al., 1995; Geiger et al., 1995; Mullen et al., 1999b). Since the psyllid first started spreading in 1984, a considerable research effort has been mobilized to examine the problem and provide options for its control and management (Withington et al., 1987; Napompeth and MacDicken, 1990; Ciesla and Nshubemuki, 1995). General overviews of the psyllid problem were provided by Napompeth (1990), Bray (1994) and Geiger et al. (1995) and of the biology of H. cubana by Beardsley (1986), Waterhouse and Norris (1987), Hodkinson (1989) and Muddiman et al. (1992). The dramatic spread of the psyllid westward from Central America in 1985 to almost encircle the globe within a decade is documented in detail by Muddiman et al. (1992) and Bray (1994). Attempts to document and quantify the impact of psyllid damage have been made by Mella et al. (1990) and Oka (1990).The possibility of identifying and using psyllid-resistant genetic material within Leucaena was proposed by Bray and Sands (1987), Sorensson and Brewbaker (1987) and Bray (1994) as one option to deal with the psyllid problem, alongside other measures such as biocontrol (reviewed by Mitchell, 1987; Nakahara et al., 1987; McClay, 1990; Waage, 1990). The possibility of using psyllid resistant species directly or through hybridization was discussed by Bray et al. (1990). Numerous studies have shown that L. diversifolia is moderately psyllid resistant (Sorensson and Brewbaker, 1984, 1986, 1987; Bray and Woodroffe, 1988; Wheeler, 1988; Wheeler and Brewbaker, 1989, 1990; Mullen et al., 1999b). However, there appears to be considerable variation in psyllid resistance among accessions within L. diversifolia, ranging from highly resistant to highly susceptible, with the widely planted K156 accession among the most susceptible (Mullen et al., 1999b).Camptomeris leaf spot is caused by Camptomeris leucaenae. Camptomeris causes black spots or patches on the underside of the leaflets and chlorosis, loss of leaflets or whole leaves, and some dieback often associated with secondary pathogens (Lenne, 1980). It is a potentially serious disease of L. leucocephala causing reduced forage yields and quality particularly in areas with >2000 mm rainfall (Lenne, 1980, 1991). Although Camptomeris is reported as a disease of L. diversifolia by Ipor (1997), initial indications from trials in Colombia are that L. diversifolia, is more resistant to Camptomeris than L. leucocephala (Lenne, 1980; Moreno et al., 1987). Ipor (1997) notes gummosis as an important disease of L. diversifolia. The cause of gummosis remains uncertain, but appears to be a canker caused by a fungus in the genus Fusarium.High proportions of seeds of L. diversifolia in Latin America are eaten by four different bruchid beetle species in the genus Acanthoscelides (Hughes and Johnson, 1996; Hughes, 1998b). So far only one of these bruchid species, Acanthoscelides macrophthalmus, has been accidentally introduced outside Latin America (for example in Australia, Jones, 1996), but deliberate introduction for biocontrol of weedy L. leucocephala is being considered in South Africa (Neser, 1994, 1996). Outside Latin America, other seed beetles may also heavily predate Leucaena seeds. Amongst these records, it appears that seeds of L. diversifolia are more resistant to Araecerus levipennis in Hawaii and Araecerus fasciculatus in the Philippines (Braza and Salise, 1988; Ipor, 1997) than L. leucocephala.

L. diversifolia can be used for soil improvement, soil conservation and erosion control in diverse agroforestry combinations and systems including alley farming, live-barriers on terrace boundaries, shelterbelts or windbreaks, or simply as dispersed trees over crops, in similar ways to its better known relative L. leucocephala. L. diversifolia leaves are very small and fragile and decompose quickly (with a 7-day nitrogen half-life) providing a very rapid, short-term influx of nutrients. However, because they decompose so rapidly, they have little value as mulch for weed control, which is widely recognized as one of the main benefits of alley farming, particularly in the humid tropics. L. diversifolia can also be used in wider land rehabilitation and re-vegetation efforts. Weediness is likely to be a problem in many agricultural situations or in land rehabilitation (Hughes, 1998b; Hughes and Jones, 1999).The wood of L. diversifolia is broadly similar to that of L. leucocephala, the properties of which have been thoroughly investigated and documented (Bawagan, 1983; Pound and Martinez-Cairo, 1983; van den Beldt and Brewbaker, 1985). Most authors have emphasised the potential to use Leucaena wood for a wide range of products including domestic and industrial fuel, including dendrothermal energy generation, poles, posts, sawn timber, furniture, parquet flooring, particle board and pulp. However, the potential to use L. diversifolia for saw timber is greatly limited by its generally small dimensions, usually not greater than 30 cm diameter, its branchiness, which limits lengths of clear bole available and means wood is often knotty, and its high proportion of juvenile wood. Nevertheless, there is growing use of small dimension sawnwood in a number of industries, such as flooring, which might include L. diversifolia in the future. In practice, the wood is primarily used for fuelwood and charcoal for domestic household or local industrial (lime or pottery kilns) use, and for small dimension poles. Use of short-rotation L. diversifolia for poles is limited by lack of durability and susceptibility to attack by termites and wood borers. L. diversifolia provides fuelwood and charcoal of acceptable, although not the highest, quality and it is a popular fuel, often competing with alternative local species in areas where fuelwood is in short supply (NAS, 1984) but not with the higher quality fuelwoods obtained from species of Acacia or Prosopis.Compared with L. leucocephala, leaves of L. diversifolia have lower nutritive value in terms of lower palatability, digestibility, intake and crude protein content, and higher condensed tannin content (Stewart and Dunsdon, 1998; Dalzell et al., 1999; Faint et al., 1999), resulting in lower animal production (Jones et al., 1999). However, it must be remembered that L. leucocephala is one of the foremost, highest quality and most palatable tropical fodder trees, often being described as the 'alfalfa of the tropics' (Jones, 1979, 1994; Pound and MartInez-Cairo, 1983; NAS, 1984; Bray, 1986; Brewbaker, 1987b, Shelton and Brewbaker, 1994). Leaf quality of L. leucocephala compares favourably with lucerne (Medicago sativa) in feed value except for its higher tannin content (Jones, 1979) and mimosine toxicity to non-ruminants (Bray, 1995). Thus, although not as high quality as L. leucocephala, L. diversifolia may still provide an acceptable livestock fodder with high crude protein content.Leaves of Leucaena species have also been widely used for green manure in cropping systems. The value of Leucaena leaf litter as a fertilizer from trees maintained over crops is recognized by farmers in Central America, Indonesia and the Philippines (Dijkman, 1950). In parts of Jamaica, Indonesia and the Philippines, L. diversifolia has been used for several decades as a shade tree over tea or coffee with widely recognized benefits in terms of soil fertility. L. diversifolia is likely to have potential in alley farming. Its leaves are fragile and decompose quickly providing a very rapid, short-term influx of nutrients related to a low carbon/nitrogen ratio but little value as mulch for weed control which is widely recognized as one of the main benefits of alley farming, particularly in the humid tropics.

No specific information on the control of L. diversifolia is available, but it may be assumed that control methods used for the closely related L. leucocephala may be suitable.

L. diversifolia forms a thornless, fast-growing, nitrogen-fixing, typically single-stemmed, light-demanding tree and is adaptable to a wide range of production systems including fodder banks managed at close spacing under regular and intensive lopping, pure plantations at a wide range of spacing, and a variety of hedgerow systems for fodder or green manure. It resprouts vigorously under a wide variety of coppicing or pollarding regimes.

Propagation, establishment and silviculture of Leucaena are well-documented, as reviewed by Pound and Martinez-Cairo (1983), NAS (1984), van den Beldt and Brewbaker (1985), Brewbaker (1987b), Hocking (1993), Luna (1996), Jones et al. (1992, 1997). While most of this literature refers to L. leucocephala, silvicultural practice is similar for L. diversifolia (Ipor, 1997).L. diversifolia is a self-fertile, precocious and abundant seed producer on a range of sites and, once introduced, it is generally easy to obtain large quantities of seed. Seed collection, extraction, processing and storage are straightforward (Hughes, 1998b). There are between 50,000 and 80,000 seed/kg. Seed is often heavily infested with bruchid or other seed-feeding beetles. Sunning seed after extraction helps to ensure beetles emerge. Damaged seed can then be removed either using a gravity table separator or flotation in water (Hughes, 1998b). The hard impervious seed coat inhibits water uptake and seed requires pretreatment before sowing to promote rapid and uniform germination. Mechanical, hot water and sulfuric acid treatments have all been used successfully (Pound and Martinez-Cairo, 1983; van den Beldt and Brewbaker, 1985; Hawkins and Ochoa, 1991; Ipor, 1997; Hughes, 1998b). Hot water treatment by soaking in water at 80°C for 3 minutes followed by washing in cold water has been most widely used although mechanical nicking is likely to give higher germination for small seedlots.L. diversifolia has the ability to form a symbiotic association with Rhizobium root nodule bacteria, which are able to fix atmospheric nitrogen. Effective nodulation has been lacking in certain environments due to lack of suitable strains of Rhizobium in the soil and inoculation may be required (Halliday and Somasegaran, 1983). Rhizobium strain TAL1145, developed by NifTAL (Nitrogen Fixation in Tropical Agricultural Legumes) has been shown to be an elite strain for L. diversifolia (Somasegaran and Martin, 1986). Despite application of a wide range of possible techniques including rooted stem cuttings, tissue culture, grafting and air-layering, successful vegetative propagation has been limited to experimental rather than commercial operations (Brewbaker, 1987b; Osman, 1995), although research is in progress to perfect vegetative propagation of Leucaena.Nursery procedures for L. diversifolia are straightforward and seedlings can be grown in a variety of ways (reviewed by Pound and Martinez-Cairo, 1983; van den Beldt and Brewbaker, 1985; Hellin and Gomez, 1991). Seedling vigour of L. diversifolia is poor (Ipor, 1997) and seedlings are significantly slower growing than L. leucocephala (Hellin and Gomez, 1991) requiring 8-12 weeks to reach 15-30 cm height. Establishment normally relies on container-grown nursery seedlings rather than direct sowing. Site preparation is important as slow early growth makes young transplants susceptible to competition from weeds posing an important limitation in establishment.Data on suitable spacings for L. leucocephala have been successfully followed for L. diversifolia. For wood production, maximum total yields are obtained at close spacings (10,000-20,000 trees/ha) (van den Beldt, 1983; van den Beldt and Brewbaker, 1985; Brewbaker, 1987b) which are optimal for fuelwood plantations where small diameter material, harvested on short 2-3 year rotations is required. For larger poles wider spacings (5,000-10,000 trees/ha) and longer, 3-6 year rotations are required. One advantage of Leucaena is its ability to maintain high wood yields over a wide range of rotation lengths, stand densities and systems of management (Brewbaker, 1987b). L. diversifolia coppices readily, but may require thinning of coppice resprouts for rapid return to optimal stem densities after cutting.For fodder production high plant densities (50,000-150,000 plants/ha) are also recommended for pure plantings which are coppiced to produce highly branched shrubs that can grow quickly to intercept light after cutting. Low, but at least 60 cm minimum height, hedge management with a 2-4 month cutting interval (moisture permitting) is now standard for Leucaena hedgerow systems (Brewbaker, 1987b).

High yield in cool, tropical, highland climates has been a major factor prompting the promotion and adoption of L. diversifolia (Brewbaker et al., 1988). On such sites L. diversifolia can produce high leaf dry matter yields in the range 10-16 tonnes/ha/yr (Ipor, 1997). Wood yields from L. diversifolia over short (2-5 year) rotations as high as 55-65 cubic metres/ha/yr have been reported from highland sites in Hawaii. This is well in excess of yields obtained from L. leucocephala (Brewbaker et al., 1988).

L. diversifolia is a self-compatible tetraploid of probable hybrid origin. Harris et al. (1994) showed that the most likely maternal parent species is L. pulverulenta but the paternal parent remains uncertain. Until recently L. diversifolia was considered to occupy a restricted distribution in central Veracruz, Mexico (Brewbaker, 1987b; Pan, 1988; Pan and Brewbaker, 1988; Zarate, 1994; Ipor, 1997). Efforts to evaluate the potential of L. diversifolia were restricted to accessions collected from that restricted area, with two accessions, K156 and K784, both collected near Fortín in Veracruz, Mexico noted as outstanding. Recent taxonomic work (Hughes, 1998b) has shown that L. diversifolia is much more widely distributed than originally thought, across five States in south-central Mexico and in northern Guatemala. More comprehensive provenance seed collections sampled from across this wider distribution have now been assembled (Hughes et al., 1995; Bray et al., 1997; Hughes, 1998b), but it is too early to draw conclusions about patterns of provenance variation based on the handful of trials that include this new material.Artificial hybridization has been the main thrust of breeding efforts in Leucaena, used to overcome the limitations of L. leucocephala and its inherent lack of genetic and useful diversity (Brewbaker and Sorensson, 1990). L. leucocephala has been the most important parent in hybrid programmes and its hybrid with L. diversifolia (designated as KX3 by the University of Hawaii) has proved to be one of the most promising artificial hybrids produced so far (Brewbaker et al., 1988; Brewbaker and Sorensson, 1990; Sorensson, 1995; Austin et al., 1999). The L. leucocephala x L. diversifolia hybrid also occurs spontaneously wherever the two species are juxtaposed in cultivation, and is documented from Mexico, Guatemala, Jamaica, Martinique, the Philippines and Papua New Guinea (Hughes, 1998a, 1998b; Hughes and Harris, 1998). Hughes and Harris (1998) named it as L. xspontanea. KX3, or L. x spontanea, like its parents, is self-fertile, seedy, fast growing and potentially weedy (Hughes and Jones, 1999), and intermediate in psyllid resistance and fodder quality between L. leucocephala and L. diversifolia.

The main disadvantage of L. diversifolia is its susceptibility to defoliation by Heteropsylla cubana. However, some accessions of L. diversifolia are moderately psyllid resistant compared with the widely planted L. leucocephala.L. diversifolia, and its hybrid with L. leucocephala, are aggressive colonizers of ruderal sites and secondary or disturbed vegetation in Mexico with many of the weedy traits (precocious flowering and fruiting, abundant seed production, self-fertility, hard seed coat, and ability to resprout after fire or cutting) of L. leucocephala (Ipor, 1997; Hughes, 1998b; Hughes and Jones, 1999).