Identification, Symptoms and nature of Damage: Termites

IntroductionTermites are polymorphic social insects and live in large communities in above ground earthen mound called termitarium or in subterranean galleries. Termite nest is very intricate network of galleries and sub- and sub-sub galleries. Termites cause damage to crops, trees, timber, furniture, books and other materials in subtropical and tropical environments. In general, rainfed crops are infested more than irrigated ones.

Termite termitariaCourtesy: www.savethekimberley.com

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Identification

In India, termites belonging to families Macrotermitidae, Microtermitidae and Odontotermitidae are main termite species. Macrotermes are mound building species while Odontotermes make galleries underground and on trees. On the other hand, microtermes build perforated underground nest.

Four castes of termites are structurally and functionally distinct forms.

Termite queenCourtesy: Entomology Division, IARI, New Delhi

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Termite castesA. Primary reproductives: These have two

pairs of large membranous wings, which are shed after they have swarmed in the process of founding new colonies. Swarming takes place during evening hours after pre-monsoon showers. Primary reproductives are adapted for short aerial life after which they form queen and king of colony. King and queen live in royal chamber, several feet below soil surface. Queen is several inches long and functions as a egg laying machine. Queen may live for 15-50 years. Termite colonies may harbour over a million individuals derived from single pair of queen and king.

Swarming adults

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B. Supplementary reproductives: Members of this caste have no aerial life. These are not normally found in colonies headed by original king and queen. They appear after a lapse of several weeks if one or both of king or queen die.C. Workers: Workers are numerically the most important members of the community. Usually pale in colour, they look more like nymphs than adults of other castes. The head is directed downwards. Termites, which we generally see in field or in household are workers.

Termite workers

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Duties of workersThey take no part in reproduction on defence of colony. However, all duties practically devolve upon the members of this caste. They exhibit marked care for eggs and young ones and in times of danger remove them to safe places.They also feed and tend queen, forage for food and in fungus growing species, cultivate fungus gardens. In subterranean species, the workers excavate galleries and tunnels that serve as nest. In mound building species, they construct termitarium and repair damage to it. It is the workers that destroy crops, timber, wood-work and other materials.

Tree damaged by termites

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D. Soldiers

Soldiers constitute the most specialized members of the community. These can be readily recognized by strongly sclerotized heads. They are specialized for defence of the colony. They protect colony from ants and other vertebrate predators. The typical soldier attacks with its mandibles, which pierce and slice.

Soldier

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DamageTermites greatly damage crops and trees in subtropical and tropical environments. In general, rainfed crops are infested more than irrigated ones especially debilitated by stress such as drought or irregular rainfall. Damage to crops or structures is done by workers. They damage the crop from sowing to harvesting. Termites feed on underground plant parts such as roots and stems.

Termite galleries at soil surface

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As a result, plants get detached from their base and dry up. Infested plants can be easily pulled out. Soil also gets filled in stems of damaged plants.

Crops such as groundnut, sugarcane, sorghum, bajra, maize, arhar, wheat, gram, and fruit and forest trees suffer heavy termite damage.

TermitariaCourtesy: http://farm3.static.flickr.com

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Cultural and mechanical methods in termite management

Undertake deep summer ploughing to destroy termite galleries.

Destroy termitaria and fill exposed holes with water.

Kill queen through nest excavation. Dispose off crop residues. Apply only rotten FYM and never use fresh FYM. Use wood ash in nursery and around tree bases. Adopt appropriate intercropping. Maize and beans

intercropped together suffer less from termites.

Maintain crops in sound health through balanced fertilizer applications. Unstressed

crops are less damaged. Cover inter-row space with vegetative matter to

divert termites from crop plants.

Summer ploughing & flooding

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Let’s sum upTermites are polymorphic social insects and live in large communitiesin above ground earthen mound called termitarium or in subterranean galleries.

Four castes of termites are structurally and functionally distinct forms.

Queen may live for 15-50 years. Termite colonies may harbour over a million individuals derived from single pair of queen and king.

Soldiers constitute the most specialized members of the community. These can be readily recognized by strongly sclerotized heads. They are specialized for defence of the colony.

Workers are numerically the most important members of the community. All duties of the colony except reproduction practically devolve upon the members of this caste.

Termites greatly damage crops and trees in subtropical and tropical environments. They feed on underground plant parts such as roots and stems.

Deep summer ploughing, queen killing, clean cultivation, use of rotten FYM, mulching and irrigation etc. help to reduce termite incidence.

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