Termites

Summary

Often called“white ants�?. However, termites are not ants but fairly closely related to cockroaches, while ants are closely related to wasps. Termites are a very large, distinct insect group with hundreds of species occurring inAfrica. A number of these species are crop pests with maize being one of the most affected crops. Various species can cause damage to the stems and roots of seedlings and mature plants which can result in significant yield losses. Not all termite activity is detrimental to farmers however. Some termites may improve soil quality by building tunnels in the ground and improve penetration of air and water into the ground as well as adding organic matter to the soil.

Common Names

White ants, termites

Taxonomic Position

Phylum: Arthropoda;Class: Hexapoda (Insecta);Order: Isoptera;Family: Termitidae (Higher termites with intestinal bacteria) has the most numerous pestiferous groups; Genus: several but important  ones in East Africa (as pests) are Allodontermes species, Ancistrotermes species, Macrotermes species, Microtermes species, Odontotermes species and Pseudacanthotermes species

Origin and Distribution

Termites occur worldwide especially in the tropical and subtropical regions. Africa however, has the largest diversity of termites.

Description

Termites are soft-bodied insects occurring in three forms (castes): reproductives, workers, soldiers. There are hundreds of species of termites inAfrica that look similar but can be distinguished by experts by features of the head , particularly the mandibles (“jaws�?).

 

Reproductives

The reproductives are sexual forms and comprise the “queen�? and her consort, the “king�?. The reproductives have four wings that are similar in appearance and length and extend beyond the abdomen. They swarm in the wet/rainy seasons when the soil is soft and easy to penetrate. Often swarming termites are attracted to lights and might enter houses for that reason, but cannot build their nest there, nor do they cause damage when flying inside. In a number of regions swarming termites are collected and eaten as human food. The reproductives are generally darker in colour and bigger than the workers. Once the nest is established, the queen’s abdomen becomes enlarged, and she produces thousands of eggs from which nymphs (young termites) emerge. These either become soldiers, which protect the termite colony, or workers whose function is to feed the members of the colony.  Both soldier and worker forms are sterile and wingless.

 

Workers

The workers build and maintain the nest, conduct all the foraging and care for the eggs and young as well as caring for the sexuals. The workers are sterile, wingless and sometimes blind. Workers normally make up most of the individuals in the nest. In some species the workers have large and small forms; in the Macrotermitinae the larger workers are the males and the smaller workers the females.

 

Soldiers

Soldiers are specialised for defending the colony and are usually sterile females and wingless. Their heads are gold-brown in colour, greatly enlarged, heavily sclerotized (“armoured�?) with prominent asymmetric mandibles. Soldiers may also exist in different forms that show differences in mandibles and size of the insect.

Similar Species

Termites and ants are sometimes confused but there are many differences including the following: termites have straight antennae while those of ants are bent; termites have straight abdomens while ant’s abdomens have a distinct “waist�?; and winged termites have wings of equal length while those of winged ants are unequal in length. Also termites are more often found underground or in self-built galleries made of mud, while ants often prefer above ground activities. 

Life Cycle

Each termite colony is established and dominated by one queen and king. The queen produces thousands of eggs over her lifetime.

A new termite colony is usually founded when swarms of sexuals fly from their nests and to various places. After shedding their wings and following a short courtship the male and a female (future king and queen) will create a nest site with a nuptial chamber in which eggs are laid - in a crevice, by digging a hole in the soil or by excavating a tunnel in wood. Once the nuptial chamber is constructed the king and queen will mate. Initially, the queen lays only a few eggs which are looked after by her and the king. The eggs are normally laid singly. Incubation takes from 24 to 90 days. There are normally seven nymphal instars (stages) in established colonies but the number varies depending on temperature, age of colony, size of colony and relative humidity. The nymphs may grow into soldiers or workers. 

The worker’s life span is one to two years.  After a few years sexuals are released from the colony, who will in turn form new colonies.

All termites eat cellulose (e.g. from dead plant fibre) and many termites cultivate a fungus within the nest, which is a source of food (especially proteins) for the queen, king and the young.

Colonies vary considerably in size from a few thousand to millions of individuals. Nest form is variable too with drywood termites which form their (relatively small) nests in wood, subterranean termites which build their colonies below ground and those that build nests above ground that can turn into characteristic mounds. 

Pest Destructive Stage

Adult, specifically the workers will do the feeding damage.

Host Range

Termites attack a broad range of crops and other plants including trees that have a high cellulose content. Among cereal crops, maize is the most often damaged by termites.

Other crops which are damaged by termites are cotton, deciduous fruit trees, groundnuts, pasture grasses, plantation trees, sorghum, soybeans, sugar cane, tea, tobacco and wheat.   Plants are readily attacked when they have been damaged or have been under some form of stress, such as drought or sometimes even water logging.  Timber may also be damaged.

Incidentally some termites may improve soil quality by building tunnels in the ground and improve penetration of air and water into the ground as well as adding organic matter to the soil.

Host Lifestage Affected

Commonly seedling and vegetative stage but all stages of growth are susceptible

Host Plant Part Affected

Microtermes and Ancistrotermes species attack maturing and mature maize plants, while Macrotermes species cause damage to seedlings. Species of Odontotermes, Allodontermes and Pseudoacanthotermes can defoliate maize seedlings or consume the entire plant.

Damage Symptoms

Partial or total defoliation of maize seedlings but are principally damaging to maturing or mature maize plants. 

Wilting, drying up and lodging of plants when the termites attack the main root system, prop roots and stems.

Hollowed out stems or roots, often packed with soil or covered with a thin sheet of soil or galleries.

Pest Management

Detection methods

Presence of stems with galleries packed with soil or tunnels made of thin sheets of soil on soil or plant stems are indications of termite activity.

 

Cultural practices

The colony may be destroyed by excavating the mound to remove the queen but this may not work for groups that have the ability to quickly replace the lost queen. Excavating the mound may be an extremely laborious task, since the queen may be concealed at some depth.  Other cultural practices include the following:

  • Sow at a higher rate to compensate for yield losses to termites.
  • Adopt practices that promote conditions for healthy plant growth to prevent termite damage, for example, weeding, applying fertilizers, adequate irrigation, etc.
  • Plough the field to destroy the termites’ nests, runways, and tunnels and to expose them to predators, such as ants, birds, chickens, etc.
  • Practice crop rotation to reduce the build-up of termites, especially with legume crops.
  • Remove plant residues and other debris especially moist and decaying wood. 
  • Harvest at the right time, as termites often attack maize left in the field after maturity.

Biological control

Termites have a host of natural enemies that prey upon the colony-establishing alates (winged termites) during swarming and as pairs dig-in to establish new colonies, or on foraging termites or the individuals in the nest itself. Enhancing ant predation by putting out baits for predatory ants (e.g. fish bones) within the crop or transplanting of ant nests into the crop can interfere with termite foraging.  The use of entomopathogenic (insect-attacking) fungi such as Beauveria bassiana and Metarhizium anisopliae are reportedly effective against adult termites. Formulations of the fungi are applied to the stem bases or in planting holes at planting. However, termite control using predators or pathogens is not completely effective because of the termites’ social structure and behavioural responses to infected individuals and to loss of individuals to predators.

 

Chemical control

Chemical control of termites is difficult because they are difficult to access and their time of attack varies considerably. The application of chemical pesticides against termites is generally aimed at creating a barrier to prevent termite access to plants. Effective chemicals are those with a degree of persistence or are able to penetrate into the soil profile to provide any control.  Therefore, insoluble compounds or those that are not readily adsorbed onto clay particles would be of no use unless they were thoroughly mixed into the soil.   Pesticides are used principally in the form of seed dressings, applied to the planting hole or furrow treatments. Such measures are successful in field crops during seasons when termite attack is generally low but have no effect under conditions of high termite pressure.  Newer insecticides such as Fipronil give some success either as a seed dressing, or as a furrow treatment at planting, and another, imidachloprid, is effective when applied as a high-volume spray to the plant bases at the appropriate time (when attack is likely). Pesticides are poisons so it is essential to follow all safety precautions on labels.

Sources of Information and Links

Bakuneeta C. (1993). The importance of Macrotermes herus (Sjostedt) in Queen Elizabeth and Murchison Falls National Parks, Uganda. Unpublished M.Sc. Thesis. Makerere University.

Bigger M. (1966). The biology and control of termites damaging field crops in Tanganyika. Bulletin of Entomological Research, 56: 417-444.

Engel M.S. and Krishna K. (2004). Family-group names for termites (Isoptera).  American Museum Novitates, 3432: 1–9.

Harris W.V. (1949). Some aspects of the termite problem. East Africa. Agricultural Journal, 14, 155–161.

Okwakol M.J.N. (1992). The Termite Problem in Uganda. Termite Research Workshop Proceedings, August 17–19, 1992. Nairobi.

Rouland-Lefèvre C. (2011). Termites as pests of agriculture. In: Biology of termites: a modern Synthesis. David Edward Bignell, Yves Roisin and Nathan Lo (eds.). Springer

Sekamatte M.B. (2001). Options for integrated management of termites (Isoptera: Termitidae) in smallholder maize-based cropping systems in Uganda. PhD thesis. Kampala: Makerere University.

Sekamatte M.B., Ogenga-Latigo M. and Russell-Smith A. (2003). Effects of maize-legume intercrops on termite damage to maize, activity of predatory ants and maize yields in Uganda. Crop Protection, 22(1): 87–93.

Editors

Anne M. Akol, Makerere University; Maneno Y. Chidege, Tropical Pesticides Research Institute; Herbert A.L. Talwana, Makerere University; John R. Mauremootoo, BioNET-INTERNATIONAL Secretariat.

Acknowledgments

We recognise the support from the National Museums of Kenya, Tropical Pesticides Research Institute (TPRI) - Tanzania and Makerere University, Uganda. This activity was undertaken as part of the BioNET-EAFRINET UVIMA Project (Taxonomy for Development in East Africa).

Contact

BioNET-EAFRINET Regional Coordinator: [email protected]