Recent establishment of many alien insects in South Africa – a cause for concern

Any new alien insect that succeeds in reaching and establishing in South Africa is a cause for concern, especially if it is phytophagous and feeds on commercially important plants. It is important that this should be detected early and documented so that the status of the insect as a pest can be assessed. Where necessary, the agricultural sector, trading partners and neighbouring countries should be alerted and consideration given to the possibility of eradication. The rate at which these insects establish in a region gives an indication of the adequacy of phytosanitary procedures which are aimed at preventing this. The aim of this paper is to draw attention to the number of alien insect species (excluding pet insects and those introduced for the biological control of pest insects and weeds) which have recently (arbitrarily the last 12 years) established in South Africa, particularly in the Western Cape Province, and to consider possible pathways by which they have entered the country. Indications are that new introductions are taking place at an alarming rate, pointing to deficiencies in the regulatory procedures and constraints faced by the South African regulatory system. Long-distance range expansion of arthropods occurs when they are translocated from one continent or one country to another through human actions, such as travel, trade in commodities and the importation of plant material. This has often happened in the past in South Africa: a rough estimate shows that 53 of about 320 species of commercial importance discussed by Annecke & Moran (1982) have been introduced into South Africa. (In the estimate the species they consider to be ‘cosmopolitan’ and ‘African’ were regarded as being indigenous, although some of them may have been introduced into South Africa, which would increase the number of introduced species.) Among the introduced species are some of our most severe agricultural pests, like the codling moth, Cydia pomonella (L.) (Lepidoptera: Tortricidae), which arrived in South Africa in 1885 from Madeira (Giliomee & Riedl 1998). Some exotic species first arrived somewhere on the African continent and then gradually spread, reaching South Africa. Thus, the tobacco whitefly, Bemisia tabaci (Gennadius) (Hemiptera: Aleyrodidae), probably of Indian origin (Fishpool & Burban 1994), is widespead in Africa (Annecke & Moran 1982), and according to records in the National Collection of Insects, Pretoria, occurs in Gauteng, Mpumalanga, KwaZulu-Natal and the Eastern Cape Province as far south as East London. Recently, this whitefly was found at Lutzville (Northern Cape Province) and at Klipheuwel and Stellenbosch in the Western Cape (T. Swanepoel, Syngenta, pers. comm.). The potato leaf miner, Liriomyza huidrobensis (Blanchard) (Diptera: Agromyzidae), from South America is known to occur in Kenya and Zimbabwe, and was first detected in South Africa during 1999 in the Sandveld and Ceres regions (Western Cape Province), where it caused severe damage to potatoes (Visser 2000). The destructive Asian fruit fly Bactrocera invadens (Drew, Tsurutha & White) (Diptera: Tephritidae) was first noticed during 2003 in Kenya and Tanzania from where it rapidly spread in all directions (Drew et al. 2005), including southwards, to Namibia and Mozambique. In South Africa it was first caught during May 2010 in traps placed along the northern border of Limpopo, adjacent to Zimbabwe. An attempt is being made to eradicate it (http://www.hortgro. co.za/images/fresh%20notes2013%_july%2010. pdf). The larger grain borer, Prostephanus truncatus (Coleoptera: Bostrychidae), was introduced into Tanzania in the 1980s (Farrell 2000) and spread southwards to reach South Africa in 1999 (Roux 1999). Likewise, the Australian gall-inducing wasp, Leptocybe invasa Fisher & LaSalle (Hymenoptera: Eulophidae), was first detected in Africa in 2002 when it was discovered on Eucalyptus in Ethiopia. From there it moved southwards via Kenya, Tanzania and Zimbabwe and reached Pretoria in 2007 (Dittrich-Schröder et al. 2009). Two other Eucalyptus feeders probably arrived in South Africa directly from Australia. The sapsucking bug, Thaumastocoris peregrinus (Hemiptera: Thaumastocoridae), (previously thought to be