Proceedings of the Eighth International Workshop on Biological Control and Management of Chromolaena odorata and other Eupatorieae, Nairobi, Kenya, 1-2 November 2010. Zachariades C, Strathie LW, Day MD, Muniappan R (eds) ARC-PPRI, Pretoria (2013) pp 20-27 Recent spread and new records of Chromolaena odorata in Africa Costas Zachariades1,4*, Susan Janse van Rensburg2,5 and Arne B.R. Witt3 1Agricultural Research Council, Plant Protection Research Institute, Private Bag X6006, Hilton, 3245 South Africa 2Grumeti Fund, PO Box 65, Mugumu, Tanzania 3CABI Africa, ICRAF Complex, United Nations Avenue, Gigiri, Nairobi, Kenya 4School of Life Sciences, University of KwaZulu-Natal, Private Bag X01, Scottsville 3209, South Africa 5Current address: South African Environmental Observation Network, PO Box 13053, Cascades, 3202 South Africa *Corresponding author: [email protected] Two biotypes of Chromolaena odorata (L.) King & Robinson (Asteraceae: Eupatorieae) are invading sub-Saharan Africa. One (the Asian/West African biotype) is spreading from tropical West Africa and the other (the southern African biotype) from south-eastern Africa. The area invaded by the former is much greater than that invaded by the latter. Recent infestations of the Asian/West African C. odorata biotype have been confirmed from north-western Angola, the eastern Democratic Republic of the Congo, eastern Uganda, eastern Rwanda, south-western Kenya and north-western Tanzania. The infestation in north-western Tanzania, east of Lake Victoria, is large and dense and appears isolated from similar infestations, probably representing a discrete introduction. Unconfirmed reports (and therefore of unknown biotype) from southern Malawi, north-western Mozambique and north-eastern Tanzania need to be investigated. While the high altitude of regions of East Africa is expected to slow the rate of spread of C. odorata in some areas, the Rift Valley and the eastern coastline are highly suited climatically to the Asian/West African biotype and it is probably only a matter of time before these regions become invaded. It is likely that as the Asian/West African biotype spreads south, it will eventually become sympatric with the southern African biotype as it spreads north. However, it is unknown how these two biotypes will interact. It is recommended that an identification kit for C. odorata be developed and distributed, that early awareness and control programmes be developed, and that biological control be considered at an early stage of invasion in these areas. KEYWORDS: Angola; East African coast; invasive alien plant species; Kenya; Malawi; northern Mozambique; Rift Valley; Rwanda; Tanzania; Uganda INTRODUCTION morphology and aspects of its biology from the first (Zachariades et al. 2009). Strong genetic Two independent introductions of different evidence indicates that this biotype originates in biotypes of Chromolaena odorata (L.) King & Jamaica or Cuba (Paterson and Zachariades Robinson (Asteraceae: Eupatorieae) have been 2013). Both have become highly invasive and made into Africa. One biotype was probably damaging to agricultural and natural systems. introduced from Asia, where it was already a widespread invader, into West Africa (Nigeria The distribution of C. odorata in Africa was in the 1930s or early 1940s and possibly Côte most recently updated in Zachariades et al. d’Ivoire in the 1950s) (Zachariades et al. 2009). (2009). The biotype introduced into West The second biotype was first recorded as Africa, named the Asian/West African (A/WA) naturalised in South Africa in 1947 biotype, has since spread to the west as far as (Zachariades et al. 2011), and differs in the Gambia, to the north into southern Burkina 20 Zachariades et al.: New chromolaena records for Africa Faso and Chad, south-east as far as northern mosaics), C. odorata was recorded as forming a Angola, and east through the Democratic dense, tall infestation on either side of much of Republic of the Congo (DRC) (Gautier 1992; the 280km stretch of road and across all fallow Zachariades et al. 2009). The weed has and abandoned farmlands (B.J. Huntley, pers. probably reached its northerly limit in West comm. to G. Preston, 2010) (Table 1). Africa, as it has invaded the savannas adjacent to the arid Sahel region. The biotype introduced Surveys to the west as far as N’dalatando also into South Africa, named the southern African revealed the presence of C. odorata (Table 1). It (SA) biotype, has spread into much of the is likely that this is causing a high cost to the subtropical eastern parts of this country as well rural economy, now moving from food cash as into Swaziland and southern Mozambique. A crops to charcoal production. As a result, people specimen of C. odorata collected in northern are likely to become more dependent on aid Zimbabwe in the 1960s (Gautier 1992) appears from the World Food Programme (B.J. Huntley, to be of the Asian/West African biotype pers. comm. to G. Preston, 2010). (Zachariades et al. 2009), as is the weed on Mauritius (ARC-PPRI, unpubl.). Democratic Republic of the Congo Although the A/WA biotype of C. odorata is McFadyen and Skarratt (1996) and Kriticos et reported as having been present in the DRC al. (2005) showed that much of sub-Saharan since the mid-1970s (Gautier 1992), it was Africa, excluding very arid regions and those understood that infestations were restricted to south of 30°S, but including eastern the western parts of this large country. Recent Madagascar, were climatically suitable for C. reports of dense infestations of the weed, odorata. Kriticos et al. (2005) also showed that producing large numbers of seeds, in the east of the invasion of the SA C. odorata biotype the country, fairly close to the border with extended into cooler regions than would be Burundi (Namoya) and Uganda (Ituri) are predicted for the A/WA biotype. Thus the A/ therefore cause for concern (Table 1). They WA biotype of the weed, and probably the SA probably indicate that C. odorata has spread biotype, have not achieved their full invasive across the country from west to east, through ranges in Africa. dispersal of the seeds through wind, water and/ or human and mechanised traffic. Although This paper lists and describes recent confirmed both the Namoya and Ituri infestations are close infestations of C. odorata since Zachariades et to the upper limits of the reported altitudinal al. (2009), and discusses where the weed is range of C. odorata distribution, the dense likely to be already and which areas it may nature and high seed production, of the Namoya spread into, as well as giving recommendations infestation at least, imply that it is not marginal as to obtaining further locality records and habitat for C. odorata. control of incipient infestations. PREVIOUSLY UNCONFIRMED NEW LOCALITY RECORDS FROM COUNTRY RECORDS NOW COUNTRIES WHERE CHROMOLAENA CONFIRMED ODORATA WAS PREVIOUSLY CONFIRMED To confirm previous anecdotal reports of C. odorata or any other weed being present in a Angola country, it is desirable to obtain photographic The A/WA biotype has previously been records and preferably non-sterile herbarium recorded in northern Angola (Hoevers & specimens. This is illustrated by the M’boob 1996) and probably arrived in the late misidentification of Ageratina adenophora 1970s (see Gautier 1992). However, during (Spreng.) King & Robinson (Asteraceae: recent vegetation surveys conducted between Eupatorieae) as C. odorata in Zambia. This was Luanda and Uige to the north-west, through the only resolved once herbarium specimens had Dembos forests (forest and forest-savanna been identified (ARC-PPRI, unpubl. data). 21 Table 1. Countries in Africa in which Chromolaena odorata had previously been recorded, but for which new data are available. Country Coordinates Alt. (m) Year Locality description Description of infestation Observer(s) Angola 850.30'S 1314.07'E 50-850 2009 Road between Luanda Huge increase of C. odorata along B.J. Huntley (Luanda) to and N’dalatando all the roads in the moist areas on 917.83'S 1454.40'E the road to N’dalatando. (N’dalatando) of Management and Control Biological on Workshop Eighth International 850.30'S 1314.07'E 50-935 2010 Dembos forests along Tall, dense infestations along road B.J. Huntley (Luanda) to 737.0'S 15 road between Luanda and and in fields. 03.0'E (Uige) Uige DRC 4°00.12'S 27°32.90'E 960 ix.2008 Maniema Prov., Namoya, Open, artisanal goldmine. B. Bytebier, odorata Chromolaena top of Mwendamboko Disturbed, open secondary forest. W.R.Q. Luke Hill (EA 2749) 1°56.66’N 30°02.35’E 1,225 x.2010 Province Oriental, District Seems to have established itself W.R.Q. Luke, Ituri, west of Bunia, fairly recently but is very invasive; F. Bujo (+Sight 22 Mongbwalu Mine Site not as dense as Namoya site. Record) 097 and other Eupatorieae other and the and company thissugar linksbetween the Given reported in 2004 (Q. Mann, pers. comm. 2004). of Tanzania, north 366m above sea level), towards the north Mtibwa Sugar Estate (6°10.300’S 37°38.267’E, An unconfirmed sighting of reduce considerably. they which Sirari, 2km from the border with Kenya, after odorata west of Musoma, introduction from further west in Africa. North thick infestations the of DRC. non It eastern shores may of Lake Victoria is isolated, and represent indicates that the infestation a east of the south borders discrete with within Uganda north and the southern or western shores of Lake Victoria, Rwanda). This anywhere to the south Interestingly, no the Serengeti extends almost to Lake Victoria. about 50km south of Musoma, in an area where this infestation extends along road B6 only survey by oneto of us (A.B.R. Witt) indicated that >1000m above sea this area. level. The whole A area is infestations recent varied at from dense an to (2013) altitude sparse within of of about 80km by 2).