OPPORTUNITIES AND RISKS

TERMITES THREATEN INFRASTRUCTURE AND FOOD SECURITY

In many African countries, termites present a huge problem, threatening both infrastructure and food production and thus directly affecting human well-being and the potential for economic growth. Termites also pose significant threats to other goods including household furniture, paper products, many synthetic materials and food items. Globally, each year, hundreds of thousands of structures (bridges, dams, decks, homes, retaining walls, roads, utility poles, and underground cables and pipes) require treatment for the management of termites (UNEP/FAO/Global IPM Facility Expert Group on Termite Biology and Management 2003).

Africa has high termite diversity of about 1 000 different species, reflecting its topological and climatological diversity. In particular, the tropical forests of Central Africa and all of the countries in Southern Africa contain diverse and abundant termite fauna. Genera infesting wooden structures include Reticulitermes, Coptotermes, Psammotermes (Family Rhinotermitidae), Anacanthotermes (Hodotermitidae), and several species of Kalotermitidae. Mound-building species occur throughout most of the African landscape. Some species have been transported over much of Africa due to commerce and nomadic migration (UNEP/FAO/Global IPM Facility Expert Group on Termite Biology and Management 2003).

Some species directly threaten agricultural systems, as shown in Box 2. There are approximately 20-50 damaging termite species in savannah and forest ecosystems in the family Termitidae. The majority of species feed on plant material, living or dead, dung or soil rich in organic material. The greatest pest potential exists within the subfamily Macrotermitinae, which has a symbiotic association with the fungus Termitomyces (UNEP/ FAO/Global IPM Facility Expert Group on Termite Biology and Management 2003). The most economically important genera throughout Africa are Macrotermes, Odontotermes, Pseudacanthotermes, Ancistrotermes and Microtermes. These differ characteristically in their biology and mode of attack (UNEP/FAO/Global IPM Facility Expert Group on Termite Biology and Management 2003):

  • Macrotermes spp. build large mounds from which they forage outwards for distances up to 50 m in galleries. They attack plants at the base of the stem, ring-barking or cutting them through completely.
  • Odontotermes spp. build both subterranean and epigeal nests. Damage is due to feeding either under soil sheeting on the outer surface of the plants or on the roots.
  • Microtermes spp. and Ancistrotermes spp. have diffuse subterranean nests and attack plants from below ground by entering the root system and tunnelling up into the stem, hollowing it out and frequently filling it with soil.
Box 2: Major crops attacked by termites

Termites threaten key agricultural crops, which form the basis of household nutrition in much of Africa, including groundnuts, maize, sugar cane, yams and cassava. Cotton is also threatened.

Groundnuts Microtermes and Odontotermes species cause damage to groundnuts in semi-arid tropical countries of Africa, resulting in yield losses of between 10 and 30 per cent. Management measures include the use of resistant groundnut varieties, cultural practices, botanical insecticides and minimal application of synthetic insecticides either to the soil or as a seed dressing. These treatments form a barrier, which repels or kills foraging termites.

Maize Among cereal crops, maize is the most often damaged by termites. Yield losses of from 30 to 60 per cent have been reported in some parts of Africa. Microtermes and Ancistrotermes species attack maturing and mature maize plants, while Macrotermes spp. cause damage to seedlings. Species of Odontotermes, Allodontermes and Pseudacanthotermes can defoliate maize seedlings or consume the entire plant. Maize plants attacked early in the season can compensate damage with new growth. One of the options for farmers to manage termites is to sow at a higher rate. The other option is to dress the seeds with insecticides.

Sugar cane The most damage to sugar cane is done by genera Amitermes, Pseudacanthotermes, Macrotermes, Odontotermes, Microtermes and Ancistrotermes. Yield losses can be very high. In Sudan losses of 18 per cent have been recorded and in Central Africa losses of 5-10 per cent are common. In Nigeria plant germination failure of up to 28 per cent has been reported. The most common damage to sugar cane is the destruction of the planting material (setts). The usual method of prevention is to dip the setts in various formulations of chlorinated hydrocarbons before planting, or to spray them in the furrows before filling in.

Yams and cassava Yams and cassava are grown from tubers and stem cuttings, respectively, and are consistently attacked as seed pieces by Amitermes, a predominantly root-feeding species. Ancistrotermes, Macrotermes, Odontotermes, Microtermes and Pseudacanthotermes are also involved in damaging the maturing crops by hollowing out stems at ground level. The current management strategy consists of treating setts with aldrin dust.

Cotton Termite species in the genera Allondotermes, Ancistrotermes, Hodotermes, Microtermes and Odontotermes have been reported to damage cotton especially in the drier parts of Africa. Management measures include broad-scale application of chlorinated hydrocarbons or seed dressings, and baiting with chopped grass treated with insecticides.

Source: UNEP/FAO/Global IPM Facility Expert Group on Termite Biology and Management 2003

Termite control measures vary considerably across Africa, and range from manual removal of queens and nests by hand, to soil applications (topical and injection) with termicides, to baiting. For termites that attack dry wood, fumigation with methyl bromide and topical and subsurface chemical injections are the standard practice. Chlordane is widely used. The costs associated with chemical use are extensive and include (Mörner and others 2002):

  • health costs (treatment, working days lost by those ill and by those taking care of the ill);
  • costs of exceeded residue levels (leaving a proportion of produce unfit for marketing);
  • costs related to pesticide resistance and resurgence;
  • pesticide-related research;
  • costs of pesticide quality control and residue monitoring;
  • costs of pesticide regulation; and
  • costs of pesticide-related extension.

Alternatives to chemical use vary in efficiency depending on climatic factors and the species. It is imperative given the agreements under the Stockholm Convention on Persistent Organic Pollutants (Stockholm Convention) for countries to begin to develop management systems based on alternatives. Alternatives include improved building practices such as building design (site preparation, construction and regular building maintenance and inspections), physical barriers, using preservative treated timber, space fumigation, baiting systems, thermal and biological control, and safer chemicals (UNEP/FAO/Global IPM Facility Expert Group on Termite Biology and Management 2003). In general, however, changing from one chemical to another is not a long-term solution (UNEP/FAO/Global IPM Facility Expert Group on Termite Biology and Management 2003).

Complete prevention and eradication of termites is not a plausible management objective; instead the focus should be on better management, and on reducing the costs to people and the environment. Successful termite management is a process that includes the talents of construction, pest management, and building management professionals. Lastly, termite management systems are most successful and least expensive when implemented pre-construction. Conversely, they are often less successful and more expensive post-construction.