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Termite workers. Source: Wikimedia Commons http://en.wikipedia.org/wiki/File:Coptotermes_formosanus_shiraki_USGov_k8204-7.jpg
Termite workers. Photo: USDA, ARS (Public Domain). Source: http://en.wikipedia.org/wiki/File:Coptotermes_formosanus_shiraki_USGov_k8204-7.jpg
Termites, Generalised lifecycle. Source: http://www.zappestcontrolvirginia.com/pests/termites/
Maize stem damaged by termites. Image from: http://www.chem.unep.ch/pops/termites/pics/pics.htm, Photo by J.N.K. Maniania
Termite damage to maize field. Image from: http://www.chem.unep.ch/pops/termites/pics/pics.htm, Photo by J.N.K. Maniania
Termite damage to maize grain. Image from: http://www.chem.unep.ch/pops/termites/pics/pics.htm, Photo by J.N.K. Maniania
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 in
White ants, termites
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
Termites occur worldwide especially in the tropical and subtropical regions. Africa however, has the largest diversity of termites.
Termites are soft-bodied insects occurring in three forms (castes): reproductives, workers, soldiers. There are hundreds of species of termites in
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.
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 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.
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.
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.
Adult, specifically the workers will do the feeding damage.
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.
Commonly seedling and vegetative stage but all stages of growth are susceptible
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.
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.
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.
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:
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 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.
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Anne M. Akol, Makerere University; Maneno Y. Chidege, Tropical Pesticides Research Institute; Herbert A.L. Talwana, Makerere University; John R. Mauremootoo, BioNET-INTERNATIONAL Secretariat.
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).
BioNET-EAFRINET Regional Coordinator: [email protected]