Comparative Study of Resistance and Feeding Preference of 24 Wood Species to Attack by Heterotermes indicola ( Wasmann ) and Coptotermes heimi ( Isoptera : Rhinotermitidae ) in Pakistan

Termites are the major constituents of the forest ecosystem in the tropical and subtropical areas and they are well known for their capacity to damage and destroy wood and wood products of all kinds (Rashmi & Sundararaj, 2013). The interaction of soil type and moisture availability influences the distribution of foraging termites in microhabitats (Mary & Weste, 2010). A lot of research has been done on wood resistance against termites by using various timbers but very little on bamboos (Nirmala & Kenneth, 2011). Abstract The present study was conducted to evaluate the laboratory and field preference of 24 Pakistani wood species by termite species Heterotermes indicola and Coptotermes heimi. The wood species evaluated, regarding attack and damage were: Azadirachta indica (Neem), Pinus roxberghii (Chir), Dalbergia sissoo (Sheesham), Populus deltoides (Popular), Albizzia lebbeck (Shirin), Abies pindrow(fir), Alstonia scholaris (Alstonia), Erythrina suberosa (Gul-e-nister), Eucalyptus citriodora (safaeda), Ficus religiosa (Bohar), Heterophragma adenophyllum (Beeri Patta), Melia azedarach (Derek), Pinus wallichiana (Chir), Terminalia arjuna (Arjun), Acacia Arabica (Kikar), Betula utilis (Birch) Cedrus deodara (Deodar), Cordia oblique (Lasura), Mangifera indica (Aam),Ehretia serrata Moringa oleifera (sohanjana), Putranjiva roxburghii (Lucky bean), Syzygium cumini (Jaman)and Zizyphus jujube (Berry). Two weeks laboratory and four weeks field feeding trials were performed as described in standards of the American Wood Protection Association. Samples of each of the 24 wood species were individually exposed to 100 termites (10% soldiers); and termite mortality, wood mass loss and visual appearance of the samples (on a scale of 0-10) were recorded. Results indicated that by no choice feeding assay, Populus deltoides was the most preferred and Dalbergia sissoo was the least preferred among the 24 wood species tested in laboratory against Heterotermes indicola and Coptotermes heimi. Field studies by no choice feeding test against mixed termites and C. heimi indicated D. sissoo the least palatable and Mangifera indica the most palatable wood. So it is recommended that though all 24 species evaluated in the present study differ in their susceptibility to termite attack, they would require additional protection to avoid termite attack. Sociobiology An international journal on social insects


Introduction
Termites are the major constituents of the forest ecosystem in the tropical and subtropical areas and they are well known for their capacity to damage and destroy wood and wood products of all kinds (Rashmi & Sundararaj, 2013).The interaction of soil type and moisture availability influences the distribution of foraging termites in microhabitats (Mary & Weste, 2010).A lot of research has been done on wood resistance against termites by using various timbers but very little on bamboos (Nirmala & Kenneth, 2011).
In Pakistan, the most common termite species causing damage to wood and wooden structures are Coptotermes heimi (Wasmann) and Heteroterme indicola (Wasmann) and Microtermes obesi (Holmgren) and Odontotermes obesus (Rambur) Heterotermes indicola has become major structural pest of wood and wooden structures inside houses in Pakistan and has been ranked as the most destructive termite species of the Lahore.It not only destroys wood but has been found damaging paper, clothes and any cellulosic material (Manzoor, 2010) Coptotermes heimi (Wasmann) is a widely distributed termite in Pakistan and causes damaging effects in standing trees (Khalid & Hina, 2014).Termites are often regarded as decomposers of lignocellulosic waste (Lenz, M. et al., 2011;Shaomei et al., 2013).The ability of termites to degrade lignocellulose gives them an important place in the carbon cycle (Brune, 2014).Inside houses,the infestation of H. indicola is judged by galleries running on walls and ceilings.During survey of houses, it was also observed that it only eats softer part of wood and after attacking wood it always has connection with ground soil (its breeding place).Its tunnels can be observed as hanging food tunnels made of mud tubes (Manzoor, 2010).
Many wood species in Pakistan are utilized as food by termites and certain wood species are preferred by others.A study by Sheikh et al. (2010) showed that workers of O. obesus prefer Fagus sp.(beech) and Pinus wallichiana (kail) more whereas they least prefer Abies pindrow (pertal) and Cedrus deodara (diar).The importance of termite resistant (durable) timbers is environment friendly and cheap source to protect timber-in-service from attack and damage in Pakistan.Termite attack is related to the presence of resistant components which are not equally distributed to all part of plant.The occurrence of organic chemicals such as phenol, quinones, terpenoids and high concentration of lignin may also affect the areas where feeding takes place (Ayesha & Sumbal, 2012).Heartwood and sapwood contains maximum concentration of components and top of stem contains minimum (Henderson et al. 2001).Sometimes the presence of essential oils also protects plants from termite attack.Elahe et al. (2014) in their study found that Eucalyptus essential oil may be an effective toxicant with suitable contact and digestive toxicity on Microcerotermes diversus.Some of the tropical forest plantation species having natural resistance to termites may offer an alternative for the use of chemicals products (Peralta et al., 2004).Factors affecting wood consumption by termites are numerous and complexly related (Peralta et al., 2004).Most important factors are wood species, hardness, presence of toxic substances, feeding inhibitors or deterrents, presence or absence of fungi, degree of fungal decay, moisture content of wood and soil (Carter & Smythe, 1974;Nagnan and Clement, 1990).Qureshi et al. (2012) found in their study that the death of the termites is due to the mortality of their protozoan population during the period of experimentation which appears to be due to the toxic effect of corresponding wood and not because of non-feeding of the woods.It was also studied by Morales-Ramos and Rojas (2001) that different wood combinations offered to termites in laboratory trials are important in Choice feeding tests.
Keeping in view the significance of the above mentioned studies, the purpose of present study was to test the feeding preference of different wood species against two subterranean termite species in laboratory and field.The current study will also be effective in preliminary screening of naturally resistant timber species for chemical analysis in order to isolate the termite resistance components for commercial use as wood preservative and to determine which commercial species will require preservative treatment before use in regions with high termite hazard.

Laboratory bioassays
Termite source: Orphaned termite workers and third instar larvae of workers and soldiers were collected using bucket traps.The traps were brought to the laboratory, all the debris was removed and termites were kept in plastic boxes with moist filter paper.Before exposure to different wood species, termites were kept in the laboratory at (26 ± 2 o C, 80% R.H) to eliminate injured and inactive termites and kept in constant darkness.Only active and healthy termite workers were used for the experiments.Termites were kept in Petriplates (90mm×15mm) containing moist filter papers until the experiments were conducted.Termite species H. indicola and C. heimi were tested for feeding preference using No-Choice feeding test in laboratory and in field conditions.All bioassay termites were collected from three colonies i.e.LCWU, Jallo park and Changamanga.

Laboratory Preference Test
No choice laboratory tests were executed to study wood preference of two termite species H. indicola and C. heimi in the laboratory.Wooden blocks (20 x 20 x 20 mm) of each wood species were prepared, cleaned and pre weighed.Wooden blocks were dried at 100°C for 24 hours.Only one type of test or wooden block was placed in a glass Petri dish and 100 termite workers (with 10% soldiers, as naturally given in colonies) were released and kept in darkness at 26°C and 60 + 5% relative humidity for 14 days in controlled chamber.Filter paper treated with distilled water was used as control.The wooden blocks were kept suitably moist.Three replicates of wooden blocks were used for each wood.After test period the wooden blocks were recovered, dried at the same temperature at which they were dried before exposure to termite workers and the amount of wood consumed was calculated by weighing.

Field Wood Preference Test against H. indicola (Wasmann) and C. heimi (Wasmann)
The field trials were conducted at sites heavily infested with termites as evidenced from previous studies and where many active nests of H. indicola, M. obesi, Odontotermes obesi and C. heimi were located at the workshop area of Lahore College Women University, Lahore and Jallo Forest Park, Lahore.
Three replicates of each wood were prepared and wooden blocks were tied by copper wire into a bundle.Each bundle was buried at each site, 15-20 cm deep into the soil (so that they may reach the nest) for a period of one month.Each replicate was set 2 m apart from each other.At the end of experiment, wood samples were brought back to laboratory, cleaned, oven dried and weighed to determine the amount consumed.
Upon termination of experiment, wood samples were brought back to laboratory, cleaned, oven dried and weighed to determine the amount of wood consumed.Other recorded parameters were total termite-contact, which was based on either one of the three criteria: termite feeding, deposited faecal material or mud gallery built on the wood.
In both laboratory and field trials, tested wood specimens was assessed according to the Standard Method for laboratory evaluation to determine resistance to Subterranean Termites (AWPA,1997).Visual rating of the test blocks using the scale of 10 (sound, surface nibbles permitted), 9 (light attack), 7 (moderate attack), 4 (heavy attack), or 0 (failure).

Data analyses
Data in mass loss (g) were subjected to Mean, Standard Error and Analysis of variance, and difference in mass loss for each pair of wooden block was calculated by paired comparison t-test.Means were separated using Tukey's HSD test.

Results and Discussion
Results of the no-choice laboratory evaluations of the resistance and feeding preference of 24 wood species to the subterranean termites H. indicola Mcmahan (1966) studied wood feeding preference of different woods and observed that poplar and maple both ranked as "more preferred" woods, with maple being perhaps slightly above poplar, yet incipient colonies reared on poplar strongly preferred it over maple.
Results of No Choice feeding bioassay in the field for C. heimi confined to wooden blocks of different species of wood, the wooden blocks of the wooden blocks of D. sissoo, P. wallichiana, E. deodara, Pu.Roxberghii, C. deodara, A. arabica and C. oblique scored 10 for the mean visual rating, indicating that woods were sound and very resistant (VR) to termite attack with only surface nibbles were permitted.P. roxberghii, T. arjuna, A. scholaris, A.pindrow, M.azedarach, scored nine for the mean visual rating showing light attack and were identified as Resistant (R), A. lebbeck, Z. jujube, M. oleifera scored 7 for the mean visual rating, indicating moderate attacks and were identified as Moderate resistant (MR).F. religiosa, B. utilis, E. suberosa, P. deltoides and M. indica scored 4 for the mean visual rating, indicating susceptible (S) to termite attack (Table 2).So, it was observed that inside laboratory and in field studies the termites species C. heimi had the same mean visual rating.Regarding mean wood mass loss, the lowest mean wood mass loss was for D. sisso which was the least preferred while P. deltoides was the most preferred wood by the species C. heimi (Wasmann).
The results of no choice field feeding test against H. indicola indicating that damage to wooden blocks was noted at the end of the four-week test.The loss in weight of wooden blocks served as a measure of termite attack.Each block was then graded by the amount of termite damage by using an AWPA scale (1997).Analysis of variance also revealed mean difference were significantly different from one another (F, 7.859; d.f.3:8:11; P<0.001).
Regarding the mean wood mass, results also indicate that the highest mean mass loss was for H. indicola was for P. deltoides (0.42±0.0005) and lowest mean mass loss was for D. sissoo (0.019±0.00057).Similarly, the mean wood mass, results also indicate that the highest mean mass loss was for C. heimi was for P. deltoides (0.48±0.006) and lowest mean mass loss was for D. sissoo (0.04±0.006).The results indicated that the wood of D. sissoo was the least preferred and M. indica was the most preferred wood used for C. heimi.Analysis of variance also revealed that means difference were significantly different from one another (F, 7.617; d.f., 3:8, P<0.001).
Regarding feeding preferences of H.indicola and C. heimi, the basic purpose was to know which species of local timbers possesses natural resistance against termites and which timber species are palatable.Various researchers in Pakistan had studied the feeding preference of C. heimi, O.obesus and B.beesoni (Akhtar & Jabeen, 1981).Akhtar and Ali (1979) studied feeding preference of O. obesus and arranged the woods in the following descending order of preference: Populus eur-americana (S.W), Abies pindrow (H.W), Acacia arabica (H.W), Cedrus deodara (H.W), Mangifera indica, Morus alba (H.W), Pinus roxburghii (H.W) and Dalbergia sissoo (H.W).However, no comprehensive data on the feeding preferences of different wood species was available.Mcmahan (1966) studied wood feeding preference of different woods and observed that poplar and maple both ranked as "more preferred" woods, with maple being perhaps slightly above poplar, yet incipient colonies reared on poplar strongly preferred it over maple.
The present study was carried out to compare the feeding preference of two important species of termites.Regarding mean percentage mortality in laboratory trials, the highest mean percentage mortality (57.0±0.0005) for H.indicola was for the wood Pinus roxberghii and lowest mean percentage (0.045± 0.020) mortality was for Putranjiva roxburghii.For C.heimi, the mean percentage mortality in laboratory trials was highest for Cedrus deodara (73.88± 0.577) and lowest mean percentage (11.66±0.577)mortality was for Populus deltoids (Table 1).
If we compare laboratory and field wood preference for C.heimi results are almost similar, under field conditions three woods i.e.Populus deltoids, Elaeis guineensis and Mangifera are susceptible to termite attack and maximum mean wood mass loss is observed for them.
It is quite obvious that D. sisso is having high specific gravity as compared to Populus and is hard in nature, one factor may be it is less eaten by both termite species in the laboratory and in field also .Chaudhry et al., (1978) also studied natural resistance of twelve timbers to the attack of C. heimi and found that Cedrus deodara and Tectona grandis were resistant to termite attack, while Salmalia malabarica, Abies pindrow and Picea smithiana were the most susceptible.Akhtar (1981) reported that A. pindrow is resistant to C. heimi.In this study, our main question, to know which species of local timber was palatable but which possesses natural resistance against termites, was answered, and there is a need to further investigate the nature of compounds having anti-termitic properties within these woods.Manzoor et al. (2009) studied the comparative studies on two Pakistani subterranean termitespecies i.e.Coptotermes heimi and Microcerotermes championi (Rhinotermitidae, Termitidae) for Natural Resistance and feeding Preferences in Laboratory and field trials and the results of present study are in conformity with the previous ones so there is dire need to develop wood rating scales in Pakistan also.Similarly Rasib and Hina (2014) studied the feeding preferences of Coptotermes heimi and the feeding preference of C. heimiin descending order based on wood consumption as a quantitative parameter were as follows: P. euramericana > Ailanthus excelsa > Azadirachta indica > P. roxburghii > Butea monosperma > Morus alba > Bauhinia variegata > Albizia lebbeck > Dalbergia sissoo > Heterophragma adenophyllum > Erythrina suberosa > Cassia fistula > T. grandis > Mangifera indica > Eucalyptus camaldulensis > Jacaranda mimosifolia > Bambusa bamboo > S. cumini.

Conclusion
The present study was performed to determine the natural wood preferences of two subterranean species of termites C. heimi and H. indicola.Subterranean termites cause extensive damage to wood and cellulose products in temperate and tropical climates.Some wood species are preferred by termites over other species due to many factors e.g.palatability and digestibility of wood, essential oils and chemicals.Twenty four commonly used woods were tested in laboratory and field by choice and no choice feeding tests.So it was concluded that Populus deltoids and Mangifera indica were most preferred along with highest mass loss ratio, whereas Dalbergia sisso and Cedrus deodara were least preferred by the both termite species in laboratory and field tests.
and C. heimi are shown in Table1.Interpreting the objectives of the AWPA(1997)termite test relative to the present study, in No Choice feeding bioassays, the wooden blocks of D. sissoo, P. wallichiana,E.deodara,P.roxberghii,C.deodara, A. indica, A. arabica and  C.oblique scored 10 for the mean visual rating, indicating that these woods are sound and very resistant (VR) to termite attack with only surface nibbles were permitted.Pinus roxburghii, T. arjuna, A. scholaris, A. pindrow, M. azedarach, scored 9 for the mean visual rating, showing light attack and the woods were identified as Resistant (R), A. .deltoidesandM.indica scored 4 for the mean visual rating, indicating susceptible (S) to termite attack (Table1).In control, no termite mortality was recorded and tunnelling pattern was observed for both species.Inside petri dish, tunnels of H. indicola were thin and were highly branched while tunnels of C. heimi were wider and less branched.H. indicola makes tunnel to top but C. heimi makes few tunnels to top.

Table 1 .
Visual rating according to AWPA scale 1997 of 10(sound, surface nibbles permitted), nine (light attack), seven (moderate attack), four (heavy attack), or zero (failure).Difference in mass loss for each pair of wooden block indicated by *=0.05 and **=0.01 are significantly different (paired comparison t-test).Mean Visual Rating, Mean Wood Mass loss and mean percentage mortality of different wood species during (No Choice feeding) bioassay against H. indicola (Wasmann) and C. heimi (Wasmann) workers exposed under laboratory conditions. *

Table 2 .
Mean Visual Rating and Mean Wood Mass loss of various wood species during No Choice feeding bioassay against C. heimi (Wasmann) in the field.
Wood is soft, with a specific gravity of 0.59 and a calorific value of 4910 kcal/kg Hard, moderately strong Fuel, fruit, implements, erosion control and medicinal (fruit for cough, chest diseases)Appendix.Table showing Density, Strength and uses of different wood species used in the study.Hard, heavy and resilient Construction, fuel, fruit, medicinal (fruit is a carminative, seed for treatment of diabetes), tannin, shelterbelts, apiculture, paper pulp, shade, fodder and roadside planting 19 Syzygium cumini (S.C) Specific gravity of 0.70 and a calorific value of 4800 kcal/kg.Hard, heavy and resilient Construction, fuel, fruit, medicinal (fruit is a carminative, seed for treatment of diabetes), tannin, shelterbelts, apiculture, paper pulp, shade, fodder and roadside planting 20 Zizyphus jujube (Z.J) Specific gravity of 0.93 and a calorific value of 5900 kcal/kg.Strong and durable Fruit, lumber and construction, chipboard, ornamental, medicinal (ripe fruit is a laxative, seeds are astringent and vermifuge) and food pickels Appendix.Table showing Density, Strength and uses of different wood species used in the study (Continuation).