Biocontrol News and Information 27(1), 1N–26N pestscience.com General News The Dilemma of Prosopis: Is There a Rose The last article, from South Africa, evaluates the Between the Thorns? status of Prosopis in that country and the conflicts of interest it has created. It addresses many of the The genus Prosopis contains species with outstand- questions raised in the articles above, discussing ingly useful qualities: they grow in arid and semi- from South Africa’s position of experience the limita- arid zones and give high yields where little else will tions of and possibilities for both utilization and grow. They produce high-quality wood for fuel and control, including biological control – also consid- timber, seeds with varied uses as human and animal ering in this context its obligations as part of the food, and other non-wood products. Species from the African continental community. New World have been introduced into Africa, Asia and Australia over the last 200 years. In some coun- These articles are followed by a tribute to Daniel tries, however, introduced Prosopis has become a Gandolfo, who died in January 2006. He worked on highly invasive weed, covering large tracts of land many weed projects for different cooperators, but his with impenetrable thorny thickets and rendering it inputs into Prosopis biocontrol research will be with unusable. It can even be invasive in its area of origin us forever as a result of the fact that David Kissinger in the New World. As affected countries devote named the seed-feeding weevil on which Daniel worked (see South African article, below) Coelo- increasing amounts of time and money to controlling cephalapion gandolfoi. infestations that encroach on vital land resources, with limited success, is it right to continue to pro- mote the use of Prosopis? Or does integrated management and improved germplasm, arising from Implications of Uncertain Prosopis Taxonomy better understanding of the taxonomy of the genus, for Biocontrol provide expanding opportunities for a much-needed Prosopis species are notorious for being difficult to resource in impoverished and marginal lands? identify: there are so many similar species, with vari- eties and other subspecific designations just adding The dilemma is accentuated by the confusion about to the confusion. To this, add highly variable phe- exactly what genetic material is present in the var- nology, frequent hybridization, and changing ious parts of the world, because different species nomenclature, and the picture becomes cloudier still. have very different properties in terms of utility and In this taxonomic fog, scientists have been host- invasive potential. The first article describes how testing a range of insects on several Prosopis ‘spe- conventional and molecular taxonomic approaches cies’, and genus-specific agents have been approved are beginning to unravel the identity of various pop- for release (with potential implications for native Old ulations of Prosopis. However, this will not provide World species, see ‘Safeguarding valued Old World all the answers as species tend to hybridize, and native Prosopis species from biocontrol introduc- invasive populations in some countries behave very tions’, this issue). differently from the parent stock. This is highlighted in the second article, which describes how a study of Taxonomists can tell the difference between species Australia’s largest Prosopis infestation found that by looking carefully at the flowers and leaves, and important invasive characteristics were accentuated scientists have accurately identified them by in this hybrid population. assessing their DNA, enzymes or other molecular features. However, the problem in the field remained Biological control is a popular choice against invasive that in many regions it was impossible for people to plants in environments where the extent of the inva- find out what species they had. Common confusions existed between P. glandulosa, P. velutina and P. sion, and lack of resources and infrastructure make juliflora, P. chilensis and P. juliflora, and P. pallida other approaches impractical or uneconomic. Many and P. juliflora, all hopefully resolved since the pub- Prosopis invasions fall into this category, courtesy of lication of Identifying tropical Prosopis species: a their spread in marginal, sparsely populated, remote field guide in 2004 (see Bibliography, below). This areas. The third article sounds a note of caution for arose from on-going work in the UK at Coventry Uni- biological control in the Old World, pointing to the versity, looking specifically at the confusion between need for protecting increasingly rare native Prosopis P. juliflora and P. pallida, involving the analysis of species that are key local resource trees. The fourth thousands of leaf samples from herbaria and sent in article describes a biocontrol initiative on Ascension from around the world for identification. This study Island, but sounds another note of caution about the took as its starting point the use of molecular limitations of agents deployed so far. The fifth article markers to confirm P. juliflora and P. pallida as dis- argues that biological control has not and will not tinct, closely related species. Also revealed was the provide a solution to managing Prosopis, and, fact that P. juliflora is a tetraploid species while P. pointing to the many uses of Prosopis in the New pallida is diploid. With the support of ploidy and the World, calls for utilization to be given a more promi- molecular studies, it has proved possible to develop nent role in integrated management strategies. simple identification keys based on foliar characters. Are we on your mailing list? Biocontrol News and Information is always pleased to receive news of research, conferences, new products or patents, changes in personnel, collaborative agreements or any other information of interest to other readers. If your organization sends out press releases or newsletters, please let us have a copy. In addition, the editors welcome proposals for review topics. 2N Biocontrol News and Information 27(1) To date, the authors have positively identified the Conservation. presence of either or both species in 28 countries. An (available on-line: www.kluweronline.com) important finding has been that the ‘common’ Pro- sopis in northeast Brazil, Cape Verde and Senegal is Pasiecznik, N.M., Harris, P.J.C. & Smith, S.J. (2004) actually P. pallida and not P. juliflora as generally Identifying tropical Prosopis species: a field guide. thought. Also, the recent identification of P. pallida HDRA, Coventry, UK. 30 pp. ISBN 0 905 343 344. in Kenya, Mauritania and India suggests that it is http://hdra.org.uk/international_programme/ more widely distributed than previously considered. ip_publications.htm This is especially significant considering that it is not only less invasive than P. juliflora but also one of the Pasiecznik, N.M., Felker, P., Harris, P.J.C., Harsh, most highly valued members of the genus, with much L.N., Cruz, G., Tewari, J.C., Cadoret, K. & Maldo- sweeter pods, a more erect form and generally fewer nado, L.J. (2001) The Prosopis juliflora – Prosopis thorns. If efforts are to be made to increase the utili- pallida complex: a monograph. HDRA, Coventry, zation of Prosopis where introduced (see other UK. 162 pp. ISBN: 0 905343 30 1. http://hdra.org.uk/ articles on Prosopis in this issue), P. pallida could international_programme/ip_publications.htm prove very useful, though not if permanently harmed by a biocontrol agent intended for its invasive and Ramírez, L., de la Vega, A., Razkin, N., Luna, V. & much more common relative, P. juliflora. Harris, P.J.C. (1999) Analysis of the relationship between species of the genus Prosopis revealed by The confirmation that this useful Prosopis species is the use of molecular markers. Agronomie 19, 31–43. more widespread than previously thought adds weight to the argument for restricting classical bio- control introductions to species-specific agents. By: N. M. Pasiecznik, P. J. C. Harris, E. J. Trenchard & S. J. Smith. Nonetheless, it may be that where very closely Email:[email protected]/ related species have been identified and all are tar- [email protected] gets for control, agents proven to be specific to the group of species or ‘species complex’ could be consid- ered. This may be appropriate for P. glandulosa, P. velutina and their hybrids for example. However, P. Prosopis in Australia: the Perils of Letting the juliflora and P. pallida, though morphologically sim- Genie out of the Lamp ilar and easily confused, have very different attributes in terms of invasiveness/utility. Clearly Unlike many invasive alien plants, Prosopis (mes- any intended biocontrol agent for use in Africa and quite) also causes serious problems in its native Asia must be shown to be specific to P. juliflora and range, in the New World, where it is highly invasive. After studying the largest Prosopis population in not to attack P. pallida; however, in Australia both Australia1, we believe that invasions in the tree’s are invasive weeds. introduced range may be even worse, and even more difficult to manage, than those in its area of origin. What may prove important is that the invasive P. This has important implications for its promotion as juliflora appears to be entirely tetraploid, whereas a multi-purpose plant through tropical parts of the the productive and potentially beneficial P. pallida world. is, in common with all other Prosopis species, entirely diploid. Resolution of the taxonomy of intro- A fire tolerant Prosopis hybrid (probably P. velutina duced Prosopis in Africa and Asia is on-going but far × P. glandulosa var. glandulosa × P. pallida) was from complete, and further detailed surveys and introduced to the semi-arid Pilbara region of analyses are still required. Until these are complete, Western Australia in the 1930s as a drought fodder classical biocontrol agent testing and introduction plant and as shade for livestock2. The natural vege- should proceed with caution.