Prosopis juliflora (SW.) DC.
Common name: Prosopis, Mesquite, Algarroba bean (English); Kalapu andara (Sinhala)
Synonyms: Mimosa juliflora, Algarobia juliflora, Neltuma juliflora
Prosopis juliflorahas had an array of synonymy since the first description in 1788. Originally known as Mimosa juliflora, it became both Algarobia julifloraand Neltuma julifloraover the last two centuries before both genera were incorporated into the single, overarching genus Prosopis. Much confusion occurs when referring to old literature, because the binomial P. juliflorawas used to describe species now generally accepted as separate taxa.
Prosopis is a tree 3-12 m tall, sometimes shrubby with spreading branches; wood is hard; branches are cylindrical, green, more or less round with spins. Foliage is glabrous or somewhat pubescent or ciliate on the leaflets; spines are axillary, uninodal, divergent, paired, or solitary and paired on the same branches, sometimes absent, not on all branchlets. Therefore often corrugated or curved when dried), emarginated or obtuse, pinnate-reticulately curved. The leaflets are 6-23 mm long x 1.6-5.5 mm wide. Racemes are cylindric, 7-15 cm long, rachis puberulent; florets as usual, greenish-white, turning
light yellow as it matures.
Morphologically similar species:
Sometimes people misidentify P. julifloraas the native Acacia chundraWild (Sinhala- Kihiriya), because of the shape of its habit. P. julifloracan be distinguished by the presence of a less number of pinnae (1-3).
History of introduction:
This species was first introduced to Sri Lanka by the Royal Botanic Gardens in 1880 from its native ranging Central and South America. However, it wasn’t recognized to be invasive till it spread in coastal areas after its introduction in the 1950’s to Hambantota as a shade plant and to improve the soil quality (Wijesundara, 2010).
In Bundala National Park P. juliflorawas introduced to improve saline soils but has now become invasive and a serious threat to native flora and fauna (Algama & Seneviratne, 2000). It has now spread vastly in seashore areas of Bundala Ramsar Wetland area.
Dispersal and reproduction (pollination and seed dispersal):
P. juliflorareproduces through seed, often once they have passed through the digestive tract of browsers such as goats, cattle, elephants and other wild herbivores. It is spread along water courses and run-off areas during periods of rain and then spreads laterally from these sites.
Impact on native species and habitats:
P. julifloracan rapidly out-compete other vegetation due to its drought and salt tolerance. The thorniness and bushy habit of P. julifloraenable it to quickly block paths and make whole areas impenetrable. It’s rapid spread in Bundala seashore area has restricted the feeding ground area of wading birds.
Direct exploitation / destruction of native species:
This species can be a very aggressive invader that replaces native vegetation and takes over habitats. Negative effects include complete loss of pasture and habitats for both domestic and wild ruminants. Herbivores also experience illness and death due to eating P. juliflorapods and being pierced by the sharp and stout thorns.
The potential of P. juliflorato fight desertification and to provide fuelwood, good-quality fodder and sometimes even human food should be respected (Geesing et al., 2004). P. juliflorais a fodder tree of excellent quality for feeding almost all kinds of livestock.
Natural Threats (pests):
Bruchid beetles have been recorded to attack Prosopis seeds.
Prevention and control:
Fire has been used in conjunction with other methods in the development of integrated eradication programmes. For example, spraying with herbicides produces dead wood that will ignite and support a sustained fire with more likelihood of killing the remaining trees. Injection of plant hormones such as 2,4-D into the phloem also has tested successfully in several countries where this species has become a threat to the natural ecosystem.