DIVERSITY OF TERMITE FAUNA AND THEIR DAMAGE TO STRUCTURAL WOOD IN URBAN SYSTEMS

Transcription

1 DIVERSITY OF TERMITE FAUNA AND THEIR DAMAGE TO STRUCTURAL WOOD IN URBAN SYSTEMS 24

2 The great architect, Frank Lloyd Wright, once said "we may use wood with intelligence only if we understand it" (Hoadleg 1976). As a part of understanding wood one has to understand the role that insects play in its biodeterioration. It is possible to use wood in home construction and have it last for reasonable period of time without deterioration by insects provided proper care is taken, although long-term service of wood will vary according to the intensity and type of insect attack to which the structures may be naturally exposed. Termites are of principal importance as pests of wooden buildings or the wooden parts of the buildings. Although destruction by these creatures is relatively slow, insidious, and spotty, the total of the damage they cause places termites among the most important groups of insects (Abe and others 2000). Termites commonly known as white-ants, are medium sized, soft bodied insects with dull white to light or dark brown in colour. Thus, they are called "Kashtra Harika" (wood-feeding) in ancient Sanskrit literature. They live in colonies in nests (termitorium). They are present throughout the tropics other than the high-altitude zones. They also occur at a lesser degree in some temperate regions. Zimmerman et al., (1982) reported 70% of land being occupied by the termites in tropical and warm temperate areas of the world. Economically, they are not only the serious pests of agriculture and plantations but also they cause enormous damage to structural-wood in different types of houses in all tropical and sub-tropical countries. (Bignell and Eggleton, 1998 and 2000). The structural-wood both in urban and rural areas, is severely damaged by termites (Reddy 1982, Edwards and Mill 1986). It has been reported that subterranean termites, mainly Coptotermes species and Odontotermes species 25

3 account for 95% of the termite-damage of wood and wood-products (Roonwall 1979, Edwards and Mill 1986). Lefroy (1909) reported termites as structural-wood destroying pests as early as 1814 when the Government houses in Calcutta were damaged, and described that termite communities are so immense and their combined efforts are most effective in devastating not only wooden structures or dead plant tissue but also any material made up of cellulose (Harris 1961, Sands 1974). Harris, (1961) recorded termites as a major destroyer of insects which damage wood-works in buildings. Yule and Wylie, (1982) reported subterranean termites damaging buildings in Queenland. Akhtar, (1982 and 1983) described structural wood destroying termites and their pattern of attack in Pakistan. Harris, (1969) reported that among 1900 known species of termites approximately 151 are damageous to timber structures particularly the woodworks of buildings. Williams, (1976) reported eighteen species of termites as serious pests of timber in buildings. Of late, Edwards and Mill, (1986) reported that among 2000 or more species belonging to six families of termites, only 70 to 80 (about 4%) cause significant damage to buildings and another 4% occasionally damage the timber. In Indian sub-continent region i.e., India, Pakistan, Ceylon and Burma, out of approximately 180 species, nearly 58 were wood-destroyers damaging buildings (Roonwall and Chhotani, 1962). Bhartari, (1970) reported that more than 1800 species of termites have been identified of which 109 are known to attack structural timber. Sen-Sarma et al., (1974) reported about eight species of common structural-wood infesting termites. Reddy and Sammaiah, (1994) reported about six species of common structural wood infesting termites. 26

4 Termites are grouped according to their habitats, which are of considerable importance in determining the style of living and foraging methods. Appropriate methods to be used to prevent termite-damage, the major distinction lying between subterranean and dry-wood termites Bhartari (1970). Roonwal (1979) categorised termite as the wood-dwellers and ground-dwellers. For most practical purpose those engaged in pest control, can identify the families and group of termites into three main types such as subterranean, damp-wood and dry-wood termites, the fourth type being harvest termites. However, Karin et al,. (1987) reported that the termites have to be differentiated in two groups in relation to their way of life such as subterranean termites and dry-wood termites. Subterranean termites: They live in colonies constructing nests in soil, on the sides of trees or transmission poles, and depend principally on the soil for moisture (Karin et al., 1987). In search of food, they construct covered runways or shelter tubes or mud galleries on the ground, whenever necessary in order to protect the foraging workers (Bhartari, 1970; Roonwal, 1979; Edwards and Mill 1986). In their endless search for food, they attack any cellulose containing structures which includes papers, books, clothes, leather, carpets and different structuralwooden articles such as furniture, shelves and other indoor wood-works which are in contact with floor or wall. In exposed situations, some termites (Schedorhinotermes species and Odontotermes species) cover the wood with an extensive sheet of mud and feed underneath (Reddy 1982; Kaib 1985). 27

5 Dry-Wood termites: They live entirely within galleries in dry, sound and seasoned wood which is not in contact with the soil, as these insects able to exist without moisture (Heather, 1982; Karin et al., 1987) and thus, hardly need moisture and access to the soil (Bhartari, 1970; Edwards and Mill, 1986). They attack indoor wood-works in buildings. Their infestation increase slowly within the wood. They often remain undetected until serious structural damage has been caused. Dry wood termites are easily recognized by the presence of their granular fecal mass in galleries of the infested timber. Besides subterranean termites which are one of the most important groups of insect pests of structural wood in buildings, the dry-wood termites can also cause serious damage to structural-wood. Their incidence of attack varies from place to place. Dampwood termites: They live under high moisture condition in old trees, stumps, rotting logs and pieces of buried timber. Once established, however, they can move into sound structural wood in the buildings (Roonwal, 1979; Edwards and Mill, 1986). Among the subterranean termites, Coptoteremes sp. belonging to Rhinotermitidae are serious pests of structural wood. Bess, (1970) and Fujii, (1975) have reported Coptotermes formosanus as the most important structural pest in the Hawaiian Archiepelago. The damage of C. acinaciformes was recorded in a house in Melbourne and that of C havilandi was recorded on ceiling of a bank in Barbados. Some species of Coptotermes damaged window of different type s houses in Indonesia (Edwards and Mill, 1986). 28

6 Termites belonging to the family termitidae also cause extensive damage to structural-wood. Harris, (1961) recorded Odontotermes ceylonicus as a major pest of wood-works in building of Ceylon. Edwards and Mill (1986) reported the damage of O. badtus in the joists and door-frames in South Africa. Haverty, (1976) reported the ecology and economic significance of Microtermes annandalei. Farhat and Iqbal (1977) recorded Microerotermes heimi as a pest of man-made wooden and other cellulose structures. Harris,(1961) reported Nasutitermes ceylonicus (Holmgreen) as a major pest of wood-works in building in Ceylon. Edward and Mill, (1986) and Kumar and Thakur, (2010) have given detailed list of termites known to damage buildings in different parts of the world. They reported 16 species of sub-terranean termites in Asia (Middle East), 12 species in Far East of Asia, 5 species in Philippine Island region, 6 species in Malaysia and Indonesia, 6 species in Pacific ocean Islands, 15 species in Australia, 11 species in North America, 17 species in Central America and Caribbean region, 9 species in South America, 3 species in Europe, 8 species in North Africa, 24 species in Tropical Africa, 12 species from South Africa, 6 species in Indian ocean Islands and 3 species from Atlantic Ocean Islands. In Indian subcontinent 26 subterranean termite species have been reported as structural-wood pests (Edwards and Mill, 1986) Roonwal, (1979) has listed 19 species of subterranean termites causing major damage to structural-wood in South Asia. Subterranean termites of the genera Heterotermes extensively damaged building structures, stored products of cellulose nature, books in libraries and clothes (Roonwall, 1955). He reported H. indicola destroying a whole township seriously infesting the wooden structures in buildings. Mathur, 29

7 (1960) reported that greatest loss was caused to wood-works in buildings. Assmuth, (1913) described the nature of damage of C. heimi to wood. Roonwall, (1955) reported it as a serious pest of wooden structures in buildings. Thakur, (1980) reported C. bengalensis attacking dry and sound wooden structures like poles, doors, windows sills and rafters in Assam. Reddy (1981a) reported wooden door frames and threshold in concrete buildings in Nagaland, being heavily damaged and eaten away to the. point where they did not support the doors. Reddy and Sammaiah, (1987) reported C. ceylonicus damaging structural wood in different types of buildings in Kalaburagi urban system. Subterranean termites belonging to the genus-odontotermes were reported damaging old stored products (Kapur and Geeta Bose, 1972) and timber work in buildings (Sen-Sarma and Thakur, 1974). Roonwal and Chhotani, (1967) reported O. feae as one of the most destructive termites for wood-works in buildings and also recorded O. redemanni destroying wood-works in different types of houses. Sen-Sarma et al., (1975) reported O. distans as a wooddestroying termite infesting rotten stumps and logs and fallen timber of a variety of plants and identified it as one of the most important and common wood infesting termites in buildings. It damaged the wooden pillars supporting the walls of the Government quarters (Reddy, 1981a) O. obesus infestation was recorded on the wooden supporting of the ceilings (Reddy, 1981b). Reddy, (1982) recorded Odontotermes species as pest of building and transmission poles. Although Roonwal, (1958) reported that Microtermes obesi does not occur in buildings, Sen-Sarma et al., (1975) have reported it as one of the minor wood destroying termites infesting wood in buildings. Reddy, (1984) reported its 30

8 damage on the wooden supports of roofs and pillars of porticos of Assam type buildings. Besides destroying the structural-wood, termites also damage other cellulose materials such as bounded books and papers in libraries and houses (Johnson, 1981). Manzoor, et al., (2009); Nour, et al., (1966) reported dry wood termite Cryptotermes brevis attacking books in houses in Egypt. Harris (1969), Sand (1974) and Roonwal (1979) reported termite as pest of household materials like plastics, books and clothings. Edwards and Mill, (1986) and Sheik et al., (2010) has reported termite damage to bound books in South Africa and Barbados, and currency notes in Kenya. They have also reported Reticuloterm.es species damage to office records of French Government. Termites, thus, have a great economic impact on wood used in and around the buildings. However, it is difficult to establish the exact cost of termite damage and control. Further, the undetected or unchecked termite damage may result in large reported monetary loss. Many investigators have estimated the cost of termite control and repair of damaged wood (Mitchell, 2002; Aihetasham et al., 2014; Lund, 1967; Ebeling, 1968; Johnston et al., 1972; Moore, 1979; and Mauldin, 1982). Rizk et. al., (1982) and Khalil et al., (1982) reported damage due to termites in Egypt. Mackensen et al., (2003); Roonwal, (1979) reported loss incurred due to termite damage to structural-wood in India. However, no other literature is available on these aspects. The abiotic environmental factors influence the foraging activity and thus, the structural-wood destroying activity of termites (Waller and La Fage, 1987). Atmospheric temperature and relative humidity and rainfall play a vital role in the survival of termites. Nests in all termites including the wood 31

9 inhabiting ones provide an insulated environment for the inhabitants and their thermoregulation is governed by the nest's location internal construction and size (Sen-Sarma, 1988). In the fungus growing mound building termites constancy of temperature is maintained inside the mound throughout the year (Manohara et al., 2003; Reich 2014; Pan et al., 2011; Grasse and Noirot, 1958; Sen-Sarma, 1988). In Macrotermes species and Odontotermes species, architecture of the mound seems to play the most crucial role in thermoregulation (Lee 2007 and 2009; Sen-Sarma, 1988). Experiments have shown that air temperature and moisture content of available timber are the most important factors influencing the activity of dry wood termites (Prasad and Intodia, 2013; Williams, 1976; Steward, 1981& 1982). In Africa, some of these species need annual average temperature between 25.5 and 27.0 C whilst others can survive at a temperature as low as 19.0 C (Edward and Mill, 1986). Sen-Sarma, (1988) have provided an excellent account of relative humidity inside the mound of Neotermes exitosus and have reported that 96% of relative humidity prevailed throughout the year. High clay content inside some of mounds seems to assist in maintaining high humidity inside the nest (Sen- Sarma, 1988). Steward, (1982) have shown that C. brevis is able to accimilatise successfully to either moderately high (90%) or loss (60%) relative humidity at 29.0 C. In India, very little information is available on the effect of abiotic factors on termite activity. Agarwal (1979) has reported that the presence of alates inside the mound increased the mound temperature 30 C in May, which decreased to C soon after swarming of alates in O. microdentatus. Behaviour of the termites in response to relative humidity has been studied. 32

10 The optimum humidit y for Neotermes basei synder has been reported to be 96-98% (Sen-Sarma, 1972), for Heterotermes indicola it was % (Sen-Sarma, 1969), and for Microtermis beesoni synder it was 100% RH (Sen-Sarma, 1969), and for Microtermis beesoni synder it was 100% RH (Sen-Sarma and Chatterjee, 1966a & b). Agarwal (1979) has observed that relative humidity inside the mound of O. microdentatus fluctuated within a narrow range of 92-96% throughout the year. Similar is the case in O. obesus. High clay content inside the mounds seemed to assist in maintaining its high humidity (Sen-Sarma, 1974). However, no information is available on the influence of abiotic factors on structural-wood destroying activity of termites. Moreover, little information is available on the qualitative composition of structural-wood destroying termites and types of their damage arid their wood destroying activity in Indian urban or rural system. Not even a single research report has been published on economic loss caused by termites in different urban and rural areas in India (Reddy and Sammaiah, 1987). Therefore, the present investigation was undertaken with the objectives of identifying and understanding specific termite damages in different type of structural-wood in different types of houses, their relationship with the seasonal variation in abiotic environmental factors such as rainfall, temperature and relative humidity which influence the structural wood destroying activity of the termites, and the economic loss caused by them. 33

11 MATERIAL AND METHODS 34

12 Survey and Sampling Extensive surveys were conducted periodically during January 2012 to April 2014 which includes regular monthly surveys followed by the keen observation of termite damage to different types of structural wood in RCC, TR Houses and THs in various localities of Kalaburagi and Semi urban areas of Kalaburagi Urban systems. A total of 150 houses including Government School Buildings, Libraries, Banks and Government Office Buildings were inspected monthly in the entire urban system, selecting few standard houses of each type in a given locality. The house owners/persons concerned were requested for their co-operation required regarding the termite damage in their houses/offices. The indoor wood-works such as doors, frames, window panels, sashs, joists, rafters and wall supporting, door and window supporting frames of TH s were inspected for damage. Other cellulose material such as books in libraries, wooden almirahs in Government offices and banks including clothes used for wrapping the files in the offices and schools in all the three types of houses were also inspected for the signs of termite activity. The earthen-sheet coverings, runways (shelter tubes) and small channeled holes on the wood works made by the termites were inspected. Those found with any such type of sign of termite activity and damage were examined rending and exposing the interior portion by a sharp chisel. Presence of small mounds on the inner and outer walls and on the roof particularly on the top of the wall of these houses was also noted. 35

13 As the subterranean termites usually enter the houses through the cracks in foundations, floors and wall, spread runways up to the structural wood (Johnson, 1981), such types of cracks either in foundation or floor or walls of houses were also inspected. The termites particularly the soldiers and workers damaging there articles were collected in 80% ethanol for species identification. The intensities of the damage and deterioration were assessed by eye and quantified on the basis of five damage classes (Williams, 1973 and Beal 1979) and recorded. It has hither to been the usual evaluation method for field tests of wood samples. The five damage classes of structural wood, were given numerical symbols as follows. i) '0' no attack ii) + a few attack exploratory nibbles (10% damage) iii) ++Slight attack with the wood remaining serviceable(10% to 25% damage) iv) +++ moderate attack with wood rendered unserviceable (25% to 50% damage) v) ++++ Heavy attack with the wood rendered useless for any structural purpose (50 to 75% damage) 36